WO2023077111A1

WO2023077111A1 - Method for forming layered thermoset silicone and thermoplastic articles using additive manufacturing, articles formed therefrom and apparatus for use therein

Info

Publication number: WO2023077111A1
Application number: PCT/US2022/078943
Authority: WO
Inventors: Mookkan Periyasamy; Ronald R. Campbell; Elizabeth SASSANO; Wojciech Jan HADJUCZEK; Michael A. Hickner; Lachlan Peeke; Wenbo Liu
Original assignee: Greene, Tweed Technologies, Inc.
Priority date: 2021-10-29
Filing date: 2022-10-28
Publication date: 2023-05-04
Also published as: TW202335833A

Abstract

Methods are described for forming composite articles comprising thermoset silicon-containing polymers, that include providing a first composition comprising a first thermoset silicon-containing polymer; providing either a thermoplastic composition and/or a continuous long reinforcing fiber; printing a first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer using an additive manufacturing device; and printing either or both of an at least partial reinforcing layer comprising the thermoplastic composition using an additive manufacturing device and an at least partial layer of a long reinforcing fiber. Also described in are apparatuses for preparing composite articles comprising reinforced thermoset silicon-containing polymers that include an additive manufacturing printer having a printer drive mechanism, a first printing nozzle for forming a first layer of a first composition; and a second printing nozzle for forming a second layer of a second composition or a long reinforcing fiber, wherein the additive manufacturing printers are capable of providing two or more layers of each of the first composition and either a second composition or a long reinforcing fiber to form three-dimensional composite articles of the first and the second composition or the first composition and long reinforcing fiber or combinations thereof according to computer design models, wherein at least one of the first printing nozzle and the second printing nozzle is a pressurized printing nozzle comprising a heating mechanism in operable contact therewith.

Description

TITLE OF THE INVENTION

[0001] Method For Forming Layered Thermoset Silicone and Thermoplastic Articles Using Additive Manufacturing, Articles Formed Therefrom and Apparatus for Use Therein

CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This International PCT Patent Application claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 63/273,484, fded October 29, 2021, entitled “Method for Forming Layered Thermoset Silicone and Thermoplastic Articles Using Additive Manufacturing, Articles Formed Therefrom and Apparatus for Use Therein,” the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

[0003] The invention relates the field of additive manufacturing, particularly additive manufacturing of composites comprising thermoset elastomers, including composites having silicone-containing elastomers, through fused filament fabrication and deposition.

DESCRIPTION OF RELATED ART

[0004] Additive manufacturing, also commonly referred to as three-dimensional ("3D") printing, is increasing in popularity for rapid prototyping and commercial production of articles. Various types of additive manufacturing processes are known, including vat photopolymerization methods such as stereolithography ("SLA"), material or binder jetting methods, powder bed fusion methods such as selective laser sintering ("SLS"), and material extrusion methods such as fused deposition modeling ("FDM"), fused-filament fabrication ("FFF") and direct pellet extrusion, among others.

[0005] In vat photopolymerization methods, a liquid photopolymer resin is stored in a vat in which a build platform is positioned. An article can be formed based on a computer model of the article in which the article is represented as a series of layers or cross sections. Based on the computer model, a first layer of the article is formed using UV light to selectively cure the liquid photopolymer resin. Once the first layer is formed, the build platform is lowered, and the UV light is used to cure the liquid photopolymer resin so as to form a subsequent layer of the article on top of the first layer. This process is repeated until the printed article is formed.

[0006] In material jetting methods, an article is prepared in a layer-by-layer manner by depositing drops of a liquid material, such as a thermoset photopolymer, to form a first layer of the article based on a computer model of the article. The deposited layer of liquid material is cured or solidified, such as by the application of UV light. Subsequent layers are deposited in the same manner so as to produce a printed article. In binder jetting, an article is formed by depositing a layer of a powdered material on a build platform and selectively depositing a liquid binder to join the powder. Subsequent layers of powder and binder are deposited in the same manner and the binder serves as an adhesive between powder layers. [0007] In powder bed fusion methods, and specifically SLS, an article is formed by generating a computer model of the article to be printed in which the article is represented as a series of layers or cross-sections. To prepare the article, a layer of powder is deposited on a build platform and the powder is sintered by the use of a laser to form a layer of the article based on the computer model. Once the layer is sintered, a further layer of powder is deposited and sintered. This process is repeated as necessary to form the article having the desired configuration.

[0008] In material extrusion methods, such as FDM or FFF, a computer model of an article is generated in which the article is represented as a series of layers. The article is produced by feeding a filament of material to an extruding head which heats the filament and deposits the heated filament on a substrate to form a layer of the article. Once a layer is formed, the extruding head proceeds to deposit the next layer of the article based upon the computer model of the article. This process is repeated in a layer-by-layer manner until the printed article is fully formed. Similarly, in direct pellet extrusion, pellets rather than filaments are used as the feed material, and the pellets are fed to an extruding head and are heated and deposited onto the substrate.

[0009] A variety of polymeric materials are known for use in additive manufacturing methods. Common polymeric materials used in additive manufacturing include acrylonitrile butadiene styrene (ABS), polyurethane, polyamide, polystyrene, and polylactic acid (PLA). More recently, high performance engineering thermoplastics have been used to produce printed articles with improved mechanical and chemical properties relative to common polymer materials. Such high-performance thermoplastics include, polyaryletherketones, polyphenylsulfones, polycarbonates, and polyetherimides. [0010] While additive manufacturing methods can be used to rapidly form an article having any of various shapes and configurations, articles formed by additive manufacturing processes can suffer from weak inter-layer adhesion in the z-direction of the printed article. [0011] Currently, additive manufacturing using material extrusion three-dimensional printing (ME3DP) based on FFF and FDM is considered a highly flexible and efficient additive manufacturing technique. In this process, a thermoplastic filament is heated and then "extruded" and fused to an underlying layer. This technique is viewed in that art as potentially useful for developing manufactured components with more complex geometries using computer-assisted design.

[0012] In addition to using the materials used as noted above, there have been further attempts to develop techniques using FFF for printing soft thermoplastic elastomers such as ethylene vinyl acetate (EVA), ethylene-propylene diene monomer in a polypropylene matrix (EPDM + PP), acrylonitrile-butadiene-styrene (ABS) and styrene-ethylene -butadienestyrene (SEBS). However, such materials present challenges in processing using FFF to form articles. See, N Kumar et al., “3D Printing of Flexible Parts Using EVA Material,” Materials Physics and Mechanics 37, pp. 124-132 (2018); N. Kumar et al., “Additive Manufacturing of Flexible Electrically Conductive Polymer Compositions Using CNC- Assisted Fused Layer Modeling Process,” Journal of the Brazilian Society of Mechanical Sciences and Engineering, 40:175 (2018) and K. Elkins et al., “Soft Elastomers for Fused Deposition Modeling,” Virginia Polytechnic Institute and State University, presented in the International Solid Freeform Fabrication Symposium (1997).

[0013] As such materials are soft, they tend to lack adequate compression set and heat resistance for many applications. To provide better performance, they are generally prepared for use in the form of a compounded elastomer (i.e., a curable elastomer composition for vulcanization including a curable polymer, one or more fillers, and generally also a cure system). As such materials are processed, they form a network structure in the crosslinked rubber system that can negatively impact the ability to fabricate objects using layered FFF technology. There is a need in the art for development of such a technique as such networked structures offer the potential of finished products which should include strong interfacial bonding provided there was the ability to form them successfully with FFF or another additive technology.

[0014] It is further an issue in the art, for development of additive processible compounds in the elastomer area, that the processing characteristics of a fully compounded curable elastomeric composition are quite different from the processing characteristics of thermoplastics such as those noted above that are typically used in FFF processing. When attempting to introduce elastomers to additive manufacturing processes, particularly in the case of thermoset elastomers, in a curable compounded form, caution has to be taken to keep the materials below their cure temperature for the purpose of being able to process the material before curing it. Such materials when not sufficiently heated present further challenges for processing as they generally have a high viscosity (a problem usually addressed by application of heat). Thus, there is difficulty in maintaining processability while also trying to prevent or hold off the formation of crosslinks during processing and prior to intentional curing.

[0015] Feeding of flexible filaments using currently available three-dimensional printing equipment also poses a further challenge due to the presence of such viscosity materials and cure-prevention needs, including needing to prevent problems which arise due to buckling of the filament when heated for processing.

[0016] Such issues arise with the printing of silicone and its composites. Such materials have the potential to realize tunable functionality and heterogeneous, structural properties for a number of end applications requiring low modulus, elastomeric materials, such as medical devices, gasket and o-ring components, flexible soft electronics and food packaging, in a wide range of areas such as medical aerospace, consumer products and manufacturing industries. Molding such materials is feasible, but costly for large part manufacture, and molds and dies that cannot be re-used are costly. Changes in design need further development of new tooling. Thus, the ability to use additive manufacturing to forms such parts, while providing also reinforcement to make the additive manufacturing more feasible, is a need in the art.

[0017] In the additive manufacturing area, direct ink writing (DIW) has been used in meso- and micro-scale structures to create complex soft components. Fabricating three dimensional structures layer-by-layer in DIW, includes extruding a liquid-phase ink through a nozzle with specified pressure and depositing with digitally defined paths. In comparison with FDM, DIW typically will need to undergo a post-printing curing or sintering to consolidate the printed structure and achieve mechanical strength. Various types of DIW (e.g., droplet-based, or continuous paste-based) are available and DIW may be used for many types of materials. When preparing printed inks, rheological and mechanical properties are key considerations, the former controlling the ink’s formulation process to assess printability, and the latter properties, such as stiffness and strength must be selected to produce stable and functional structures without slump deformation or collapse. In additive printing of silicone, use of stereolithography and digital light processing are common methods for defining three-dimensional silicone structures using a single silicone ink. Such techniques, however, are relatively expensive for small quantity printing. DIW material extrusion is currently a well known way to print silicone as the nozzle dispensing method can meet deposition requirements of a wide range of fluids from low viscosity liquids to pastes. Pneumatic, pressure-actuated and mechanical systems are available for dispensing fluids for material extrusion.

[0018] However, the weakness of such materials persists, and finding a way to reinforce them adequately is a need in the art. Chopped fibers and short reinforcing fibers or additives can be used for inducing electrical properties or improve mechanical strength. Other techniques, such as changing fiber orientation and fine-tuning rheological or mechanical properties have been tried as well, including incorporation of natural fiber to reduce the cost of short fibers of carbon or glass, however, the need in the art remains. To truly increase the strength, long fiber reinforcement or other techniques are needed. Attempts to do this have included pre-impregnated filament as well as co-extrusion, fiber encapsulation and the like have also been attempted, but high cost, low adhesion and lack of external protection makes such methods not yet suitable for larger scale manufacturing.

[0019] Continuous fiber reinforced composites have been developed for additive manufacturing processes to prepare various complex structures that are light in weight with high mechanical properties. However, to date, additive printed materials have mechanical anisotropy due to the extrusion-based printing process which creates small changes in geometry during the deposition process, which influences directional strength of final parts. Thus, there is a desire to reinforce such materials.

[0020] Attempts have been made also to resolve the issue of structural support by using an extrusion head configured to extrude certain thermoplastics such as nylon or certain curable thermosets such as epoxy or urethane-based elastomers over fiber reinforcement in a single co-extruding three-dimensional printing apparatus head, wherein, in some instances, the fiber can be a single fiber or a pre-impregnated bundle. Nylon reinforced with carbon fiber, Kevlar®, or Fiberglass® printed materials made in this manner are available from Markforged, Inc. Coextruded fiber such as carbon fiber using certain elastomers including silicones are available from Continuous Composites, Inc. Such materials and process are also described, for example, in U.S. Patents Nos. 10,449,711 and 10,603,836, U.S. Patent Publication No. 2020/00369360 Al and International Patent Application Publication No. WO 2021/173795 A2. In some instances,

[0021] While developments have occurred to date, it would be desirable to find a method that would enable printing of high performance elastomers, such as silicone elastomers, that are formed from curable thermoset silicon-containing polymers that are also suitable for end uses such as, but not limited to, use in semiconductor, downhole tooling, medical devices, aerospace, defense and various other applications and markets, however, many such parts, in addition to having a broad range of operating environments, also require formation of complex geometries and require cost effective formation processes with stronger interlayer adhesion upon printing to meet end use demands.

[0022] The present invention presents ways to address the above-noted issues in the prior art. One way to reduce cost of formation of such parts and/or modify their properties to achieve acceptable end use properties that is introduced by applicants herein would be to adapt an additive manufacturing method that enables introduction of composites of difficult- to-print and/or expensive -to-print elastomers by introducing a further material with such elastomers. Forming such a composite prepared through additive manufacture provides one material in the composite to reinforce and help to strengthen the elastomer while also reducing the cost of manufacture and making the preparation of articles using such elastomers easier to print three-dimensionally. Another way, introduced by applicants herein, is to introduce a way to prepare long-fiber reinforced high performance elastomer materials formed by additive manufacturing. Thus, while there have been needs in the art for additive manufacturing of composite parts including high-performance elastomers that can provide a variety of versatile properties while maintaining an economical method for manufacture, such needs are met by the methods, composites and printed articles of applicants herein.

BRIEF SUMMARY OF THE INVENTION

[0023] The invention includes a method for forming composite articles comprising thermoset silicon-containing polymers, and articles formed therefrom as well as an apparatus related thereto. The disclosure includes one of more of the following embodiments.

[0024] In one embodiment, the invention includes a method for forming composite articles comprising thermoset silicon-containing polymers, comprising: providing a first composition comprising a first thermoset silicon-containing polymer; providing a thermoplastic composition; printing, using an additive manufacturing device: (i) a first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer using an additive manufacturing device; and (ii) an at least partial reinforcing layer comprising the thermoplastic composition, wherein the first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial reinforcing layer are printed either to be within the same layer or in successive layers.

[0025] In the method, the first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer may be printed on a substrate. The first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial reinforcing layer may be complete individual layers printed in at least two successive layers. In such embodiment, the first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer is printed on a substrate.

[0026] Alternatively, the first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial reinforcing layer may be printed so as to be within a single layer.

[0027] The first thermoset silicon-containing polymer may comprise at least one polymer selected from the group of a polysiloxane; a polyalkylsiloxane; a polydialkylsiloxane; and combinations, or co-polymers thereof. The first thermoset silicon- containing polymer may also comprises at least one functional group selected from the group consisting of hydroxyl, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkenoxy, alkynoxy, aryloxy, arylalkyl, arylalkoxy, arylalkenoxy, vinyl, carboxyl, carbonyl, halogen, heterocyclic, and fluorinated and perfluorinated groups thereof.

[0028] The first composition comprising the first thermoset silicon-containing polymer may comprise one or components selected from the group consisting of a curative, a cure catalyst, an organic peroxide, a hydrolytic crosslinker, a siloxane additive, an ultra-high- molecular-weight siloxane additive, clarifiers, UV absorbers, optical brighteners, pigments, colorants, stabilizers, flame-retardants, quartz, pyrogenic silica, carbon black, fluorinated or perfluorinated polymer additives, and nanosilica dioxide particles.

[0029] The thermoplastic composition may comprise at least one thermoplastic selected from the group consisting of polyolefins, polyoxymethylene, polyamides, polyesters, polyimides, polyarylene ethers, polyarylene ether ketones, polyarylene ether sulfones, polyphenylene oxide blended with polystyrene, polyacrylonitrile-butadiene-styrene, polystyrene-acrylonitrile, polyacrylonitrile, polystyrene, polyethylene terephthalate, polyethylene terephthalate glycol, thermoplastic elastomers and thermoplastic polyurethanes, and copolymers, blends, alloys and derivatives thereof. The reinforcing layer may comprise fibers. [0030] The method may further comprise printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer on the first at least partial layer thereof prior to printing the at least partial reinforcing layer.

[0031] The method may further comprise printing one or more additional at least partial reinforcing layers comprising the thermoplastic composition on the at least partial reinforcing layer.

[0032] The method may further comprise successively, and in an alternating manner, printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer and one or more additional at least partial reinforcing layers comprising the thermoplastic composition on the at least one reinforcing layer.

[0033] The method may further comprising compression molding the article formed by the method into a modified article.

[0034] The invention also includes a three-dimensional article formed from the various method embodiments noted above and described herein. The article may have a composite structure comprising at least one at least partial layer of the first composition comprising the thermoset silicon-containing polymer and at least one partial layer of the reinforcing composition comprising the thermoplastic.

[0035] The method may further comprise (e) providing a second composition comprising a second thermoset silicon-containing polymer; and (f) printing at least partial first layer of the second composition comprising the second thermoset silicon-containing polymer on the at least partial reinforcing layer using an additive manufacturing device. [0036] In such an embodiment, the first at least partial layer of the second composition comprising the second thermoset silicon-containing polymer may be a complete layer and the at least partial reinforcing layer may be a complete layer. Alternatively, the first at least partial layer of the second composition comprising the second thermoset silicon-containing polymer and the at least partial reinforcing layer may also be printed so as to be within a single layer, which may itself be a complete or partial layer or, in some embodiments a patterned layer.

[0037] The first thermoset silicon-containing polymer and/or any second thermoset silicon-containing polymer may each independently comprise at least one polymer selected from the group of a polysiloxane; a polyalkylsiloxane; a polydialkylsiloxane; and combinations, or co-polymers thereof.

[0038] The first thermoset silicon-containing polymer and/or the second thermoset silicon-containing polymer may also independently comprise at least one functional group selected from the group consisting of hydroxyl, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkenoxy, alkynoxy, aryloxy, arylalkyl, arylalkoxy, arylalkenoxy, vinyl, carboxyl, carbonyl, halogen, heterocyclic, and fluorinated and perfluorinated groups thereof.

[0039] The first composition comprising the first thermoset silicon-containing polymer and/or the second composition comprising the second thermoset silicon-containing polymer may independently comprise one or components selected from the group consisting of a curative, a cure catalyst, an organic peroxide, a hydrolytic crosslinker, a siloxane additive, an ultra-high-molecular- weight siloxane additive, clarifiers, UV absorbers, optical brighteners, pigments, colorants, stabilizers, flame -retardants, quartz, pyrogenic silica, carbon black, fluorinated or perfluorinated polymer additives, and nanosilica dioxide particles.

[0040] The first thermoset silicon-containing polymer and the second thermoset silicon- containing polymer may be the same or different.

[0041] The thermoplastic composition in this embodiment may comprise at least one thermoplastic selected from the group consisting of polyolefins, polyoxymethylene, polyamides, polyesters, polyimides, polyarylene ethers, polyarylene ether ketones, polyarylene ether sulfones, polyphenylene oxide blended with polystyrene, polyacrylonitrile-butadiene-styrene, polystyrene-acrylonitrile, polyacrylonitrile, polystyrene, polyethylene terephthalate, polyethylene terephthalate glycol, thermoplastic elastomers and thermoplastic polyurethanes, and copolymers, blends, alloys and derivatives thereof.

[0042] The method may further comprise printing one or more successive at least partial layers of the first composition comprising the first thermoset silicon-containing polymer on the first at least partial layer thereof prior to printing the at least partial reinforcing layer.

[0043] The method may further comprise printing one or more successive at least partial reinforcing layers comprising the thermoplastic composition prior to printing the first at least partial layer of the second composition comprising the second thermoset silicon- containing polymer.

[0044] The method may further comprise printing one or more successive at least partial layers of the second composition comprising the second thermoset silicon-containing polymer on the first at least partial layer of the second composition comprising the second thermoset silicon-containing polymer.

[0045] The method may further comprise successively, and in an alternating manner, printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer, one or more additional at least partial reinforcing layers comprising the thermoplastic composition, and one or more additional at least partial layers of the second composition comprising the second thermoset silicon-containing polymer according to a designed pattern on the first at least partial layer of the second composition comprising the second silicon containing polymer.

[0046] In the method, each of the at least partial layers of the first composition comprising the first thermoset silicon-containing polymer, each of the at least partial reinforcing layers comprising the thermoplastic composition, and each of the at least partial layers of the second composition comprising the second thermoset silicon-containing polymer may be printed as a complete layer. Alternatively, one or more of them may be printed in partial layers alone or together with other such polymer and reinforcing layers. [0047] The method may further comprise compression molding the article formed by the method into a modified article.

[0048] The method may further comprise repeating steps (c), (d) and (f) noted above to form an article based on a computer design model. The article may comprise a configuration that is a tubular or a cylindrical solid article.

[0049] A three-dimensional article may be formed by the embodiments of the method noted above having a first and second thermoset silicon-containing polymer and as described herein, may have a composite structure comprising at least one of the following at least partial layers formed of the first composition comprising the thermoset silicon- containing polymer, the reinforcing composition comprising the thermoplastic and the second composition comprising a thermoset silicon-containing polymer.

[0050] In one embodiment, the article may be, for example, and without intending to be limiting, an O-ring, a seal, a gasket, a medical device, a medical implant, or a component part thereof.

[0051] The three-dimensional article may be further subjected to compression molding to form a modified article.

[0052] The invention further includes an apparatus for preparing a composite article comprising thermoset silicon-containing polymers, comprising: an additive manufacturing printer having a printer drive mechanism; a first printing nozzle for forming a first at least partial layer of a first composition; and a second printing nozzle for forming a second at least partial layer of a second composition, wherein the additive manufacturing printer is capable of providing two or more at least partial layers of each of the first and the second composition to form a three-dimensional composite article of the first and the second compositions according to a computer design model, and wherein at least one of the first printing nozzle and the second printing nozzle is a pressurized printing nozzle comprising a heating mechanism in operable contact therewith. The first composition and the second composition may be the same or different. The first composition may comprise a first thermoset silicon-containing polymer and the second composition may comprise either a second thermoset silicon-containing polymer or a thermoplastic polymer.

[0053] The first composition may comprise the first thermoset silicon-containing polymer and the second composition may comprise the second thermoset silicon-containing polymer, and each of the first nozzle and the second nozzle may be a pressurized nozzle. In such an embodiment, the first thermoset silicon-containing polymer and the second thermoset silicon-containing polymer may be the same.

[0054] The apparatus may comprise a third printing nozzle for forming a third layer of a third composition. The third composition is the same as the first and/or the second compositions or may be different.

[0055] The at least one of the printing nozzles may be operably programmed in the computer design model to print an at least partial layer according to a design pattern. The at least partial layer that is in a design pattern may be a thermoplastic layer. The first and/or the second composition may be in the form of a filament.

[0056] The first nozzle and the second nozzle may be part of a nozzle assembly that further includes a mounting arm to stably hold the first nozzle and the second nozzle in position for tandem operation. The mounting arm may have a transversely extending support portion for supporting the second nozzle and a seat support portion having an opening therethrough to support the first nozzle.

[0057] The nozzle assembly may further comprise a nozzle assembly printer drive mechanism. The first nozzle may be a high pressure piston extruder. The first nozzle may be in communication with a pressurized source. The first nozzle may have a nozzle end portion and a heating band adapted to be positioned around the nozzle end portion for heating a composition having a thermoset silicon-containing polymer as it is printed by the nozzle.

[0058] The second nozzle may be a thermoplastic nozzle extruder. The second nozzle may be a fiber nozzle extruder.

[0059] In yet another embodiment herein, the invention includes a method for forming composite articles comprising thermoset silicon-containing polymers and long reinforcing fiber, comprising: providing a first composition comprising a first thermoset silicon- containing polymer; providing a continuous long reinforcing fiber; printing at least a partial layer of the first composition comprising the first thermoset silicon-containing polymer using a first nozzle of an additive manufacturing device; and printing at least a partial layer of long reinforcing fibers using a second nozzle of the additive manufacturing device, wherein the at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial layer of long reinforcing fibers are printed either to be within the same layer or in successive layers.

[0060] The at least partial layer of the first composition comprising the first thermoset silicon-containing polymer may be printed on a substrate. The at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial layer of long reinforcing fibers may be complete individual layers printed in at least two successive layers or one may be complete and the other partial or vice versa. The at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial layer of long reinforcing fibers may further be printed so as to be within a single layer.

[0061] The first thermoset silicon-containing polymer may comprise at least one polymer selected from the group of a polysiloxane; a polyalkylsiloxane; a polydialkylsiloxane; and combinations, or co-polymers thereof. The first thermoset silicon- containing polymer may also comprise at least one functional group selected from the group consisting of hydroxyl, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkenoxy, alkynoxy, aryloxy, arylalkyl, arylalkoxy, arylalkenoxy, vinyl, carboxyl, carbonyl, halogen, heterocyclic, and fluorinated and perfluorinated groups thereof. The first composition comprising the first thermoset silicon-containing polymer may also comprise one or more components selected from the group consisting of a curative, a cure catalyst, an organic peroxide, a hydrolytic crosslinker, a siloxane additive, an ultra-high-molecular-weight siloxane additive, clarifiers, UV absorbers, optical brighteners, pigments, colorants, stabilizers, flame -retardants, quartz, pyrogenic silica, carbon black, fluorinated or perfluorinated polymer additives, and nanosilica dioxide particles.

[0062] The long continuous reinforcing fiber(s) provided to the method and/or the long reinforcing fibers in the resulting articles may be selected from the group consisting of carbon fiber, glass fiber, boron fiber, alumina fiber, silicon carbide fiber, quartz fiber, aramid fiber, polybenzoxazole fiber, ultra-high molecular weight polyethylene fiber, polypropylene, polyethylene terephthalate, polyethylene, polyimide, polyarylesters, polyetherimide, polyvinyl alcohol, rayon, polyacrylonitrile fibers, and natural and synthetic fiber blends. The long reinforcing fibers in a further embodiment may be natural fiber(s) selected from the group consisting of keratin, flax, viscose, sisal, hemp and jute. The long reinforcing fibers are preferably selected from the group consisting of carbon fibers, aramid fibers, and glass fibers. The long reinforcing fiber may also be provided as one of a single fiber, a fiber tow, a fiber bundle, a braid, a blend of fibers, or as hybrid fiber bundles [0063] The method may further comprise cutting the long continuous fiber as the fiber leaves the second nozzle using a fiber cutting device.

[0064] Printing of the first thermoset silicon-containing polymer using the first nozzle may further comprise heating the first nozzle of the additive manufacturing device. Further, printing the long reinforcing fiber using the second nozzle may further comprise heating the second nozzle. The method may further comprise co-extruding a composition comprising an extrudable polymeric material over the long reinforcing fiber in the second nozzle. In such an embodiment, the extrudable polymeric material may be a thermoplastic composition or a second composition comprising a second thermoset silicon-containing polymer. The first thermoset silicon-containing polymer may be the same or different from the second thermoset silicon-containing polymer. The extrudable polymeric material may also be a thermoplastic composition that comprises at least one thermoplastic selected from, e.g., the group consisting of polyolefins, polyoxymethylene, polyamides, polyesters, polyimides, polyarylene ethers, polyarylene ether ketones, polyarylene ether sulfones, polyphenylene oxide blended with polystyrene, polyacrylonitrile-butadiene-styrene, polystyreneacrylonitrile, polyacrylonitrile, polystyrene, polyethylene terephthalate, polyethylene terephthalate glycol, thermoplastic elastomers and thermoplastic polyurethanes, and copolymers, blends, alloys, and derivatives thereof. The composition comprising the extrudable polymeric material may comprise one or more reinforcing fibers, such as short or chopped fibers, nanotubes, carbon nanostructures or whiskers. The first composition comprising the first thermoset silicon-containing polymer may also comprise such types of additional reinforcing fibers.

[0065] The method may further comprise printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer on the at least partial layer thereof prior to or after printing the at least partial layer of long reinforcing fibers. The method may also further comprise printing one or more additional at least partial layers of the long reinforcing fibers. The method may also further comprise successively, and in an alternating manner, printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer and one or more additional at least partial layers of the long reinforcing fibers wherein the long reinforcing fibers may optionally have a coextruded material composition extruded thereon, e.g. one comprising a thermoplastic as noted above.

[0066] The method may also further comprise printing the at least partial layer of the first composition comprising the first thermoset silicon-containing polymer in a generally transverse direction and printing the at least partial layer of the long reinforcing fibers in a second generally longitudinal direction. This pattern may also be reversed, where the first composition comprising the first thermoset silicon-containing polymer is printed in a generally longitudinal direction with the long reinforcing fibers being printed in a generally transverse direction.

[0067] The method may also further comprise compression molding the composite article formed by the method into a modified composite article.

[0068] The invention also includes in another embodiment three-dimensional composite article(s) formed from the embodiments of the method noted herein that have a composite structure comprising at least one of the at least partial layer of the first composition comprising the thermoset silicon-containing polymer and at least one of the at least one partial layer of the long reinforcing fibers. Such three-dimensional article(s) may be an O- ring, a seal, a gasket, a medical device, a medical implant, or a component part thereof or various other items as noted herein.

[0069] The method noted above in another embodiment herein may further comprise (e) providing a second composition comprising a second thermoset silicon-containing polymer; and (f) printing at least a partial first layer of the second composition comprising the second thermoset silicon-containing polymer on the at least partial layer of the long reinforcing fibers using the additive manufacturing device. The second composition comprising the second thermoset silicon-containing polymer may be introduced by alternating introducing through the first nozzle, by co-extruding that material over the long reinforcing fiber and/or by use of a third mounted nozzle dedicated to introducing the second composition comprising the second thermoset silicon-containing polymer. In such a method embodiment, the first at least partial layer of the second composition comprising the second thermoset silicon-containing polymer may be a complete layer. Further, the first thermoset silicon-containing polymer and the second thermoset silicon-containing polymer may be the same or different from one another.

[0070] The method may further comprise repeating steps (c), (d) and (f) to form an article based on a computer design model.

[0071] The method may further comprise, according to a designed pattern, printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer and one or more additional at least partial layers of the long reinforcing fibers.

[0072] The method in the embodiments noted above may also further comprise printing one or more additional at least partial layers of a second composition comprising a second thermoset silicon-containing polymer. [0073] The method in the embodiments noted above may further comprise repeating steps (c) and (d) to form an article based on a computer design model.

[0074] The invention further includes in yet another embodiment, an apparatus for preparing a composite article comprising thermoset silicon-containing polymers and long continuous fibers, comprising: an additive manufacturing printer having a printer drive mechanism, a first nozzle for forming an at least partial layer of a first composition; and a second nozzle for forming an at least partial layer of a long reinforcing fiber, a fiber cutting device positioned for cutting the long reinforcing fiber leaving the second nozzle, wherein the additive manufacturing printer is capable of providing one or more at least partial layer of each of the first composition and one or more of the at least partial layer of the long reinforcing fiber to form a three-dimensional composite article of the first composition and the long reinforcing fiber according to a computer design model, and wherein at least one of the first nozzle and the second nozzle is a pressurized printing nozzle comprising a heating mechanism in operable contact therewith.

[0075] In the apparatus, in the first nozzle, the first composition may comprise a first thermoset silicon-containing polymer. The apparatus may further comprise a third nozzle for forming a third layer of a second composition, wherein the second composition may comprise an extrudable polymeric material.

[0076] The first nozzle and the second nozzle may be configured so as to be heated in operation. The second nozzle may be configured to be capable of coextruding an extrudable polymeric material over the long reinforcing fiber.

[0077] At least one of the first and the second nozzles may be operably programmed in the computer design model to print an at least partial layer in a design pattern. The first and the second nozzles are preferably both operably programmed in the computer design model to print at least partial layers of the first composition and of the long reinforcing fiber in the design pattern.

[0078] The apparatus may be configured such that the first composition may be provided in the form of a filament. The first nozzle and the second nozzle may be part of a nozzle assembly that further includes a mounting arm to stably hold the first nozzle and the second nozzle in position for tandem operation. The mounting arm may have a support base for supporting the first and the second nozzle and is preferably operably and releasably connectable to the fiber cutting device, wherein the support base may further have respective openings therethrough to support the first nozzle and the second nozzle.

[0079] The first nozzle may be a high pressure piston extruder. The first nozzle is such an embodiment is preferably in communication with a pressurized source. [0080] The first nozzle may have a nozzle end portion having a heating band adapted to be positioned around the nozzle end portion for heating a composition having a thermoset silicon-containing polymer as it is printed by the nozzle. The second nozzle may be a long reinforcing fiber extruder. The second nozzle may also be configured to receive an extrudable polymeric material to co-extrude over the long reinforcing fiber. The fiber cutting device is preferably operable to continuously cut long reinforcing fiber at a controlled interval length while printing the at least partial layer of long reinforcing fiber. The second nozzle may have a nozzle end portion and a heating band that is adapted to be positioned around the nozzle end portion for heating the long reinforcing fiber.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) [0081] The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. At least one drawing executed in color is included herein. Copies of this patent or patent application publication with color drawings will be provided by the Office upon request and payment of the necessary fee. In the drawings:

[0082] Fig. 1 is a front perspective schematic view of an apparatus for use in embodiments of the methods herein;

[0083] Fig. 1A is a front perspective view of the apparatus of Fig. 1;

[0084] Fig. 2 is an enlarged front perspective view of a print nozzle and mounting arm for use in the apparatus of Fig. 1;

[0085] Fig. 3 is an enlarged front elevational view of the print nozzle and mounting arm of Fig. 2;

[0086] Fig. 4 is an enlarged top elevational view of the nozzle and mounting arm of Fig. 2;

[0087] Fig. 5 is a right side elevational view of the nozzle and mounting arm of Fig. 2;

[0088] Fig. 6 is a front perspective view of the mounting arm of Fig. 2;

[0089] Fig. 7 is a right side elevational view of the mount arm of Fig. 6;

[0090] Fig. 8 is a front elevational view of the mounting arm of Fig. 6;

[0091] Fig. 9 is a top elevational view of the mounting arm of Fig. 6;

[0092] Fig. 10 is a left side elevational view of the print nozzle and mounting arm of

Fig. 3; [0093] Fig. 11 is a longitudinal cross-sectional view of the print nozzle and mounting arm of Fig. 10 taken along line 11-11;

[0094] Fig. 12 is a front perspective view of a thermoplastic extruder head and a nozzle and mounting arm assembly for use in the apparatus of Fig. 1;

[0095] Fig. 13 is a bottom perspective view of the assembly of Fig. 12;

[0096] Fig. 14 is a rear perspective view of the assembly of Fig. 12;

[0097] Fig. 15 is a process flow diagram for additive printing using the apparatus of Fig. 1;

[0098] Fig. 16 is a photographic representation of an example composite part formed using the apparatus of Fig. 1 and the method herein using an embedded nylon mesh design layer and silicone;

[0099] Fig. 17 is a photographic representation of a composite article in the process of printing showing a layer of mesh nylon under a partial layer of silicone;

[0100] Fig. 18 is a photographic representation of a completed composite article showing a dark mesh seen through layers of silicone;

[0101] Fig. 19 is a photographic representation of a printed silicone and acrylonitrile- butadiene-styrene (ABS) composite article with layers of silicone (in white) and layers of ABS (in black) as a reinforcing layer;

[0102] Fig. 20 is a graphical representation of capillary rheometer data the relationship between apparent shear viscosity (in Pa-s) against the apparent shear rate (1/s) of a silicone polymer used in the Examples herein at varying temperatures to evaluate the viscosity range for evaluating the material for printing;

[0103] Fig. 21 is a photographic image of a three-dimensional tubular composite article formed using layers of silicone and nylon filament in layered composite in the Examples herein;

[0104] Fig. 21A includes SEM representations of the sample in Fig. 21;

[0105] Fig. 22 is graphical representation of a peel test used for measuring inner-layer adhesion in a three layer flat composite article for testing;

[0106] Fig. 22A is a front perspective of a test machine used in the Examples herein;

[0107] Fig. 23A is a photographic representation of a composite article formed using a

0-20-340 nylon 6,6 mesh reinforcing layer with a layer of silicone;

[0108] Fig. 23B is a photographic representation of a composite article formed using a triangle nylon 6.6 nylon 6,6 mesh reinforcing layer with a layer of silicone;

[0109] Fig. 24A are photographic representations of composite articles in the form of O- rings formed using nylon 6,6 and silicone layers; [0110] Fig. 24B is a three dimensional complex composite article formed using nylon 6,6 and silicone layers;

[0111] Fig. 25 is a representative screen capture of a three-dimensional model from SolidWorks® used in Example 4;

[0112] Fig. 26 is example of an .STL format file showing the differences between a curved model identified as CM and an exported .STL model identified as ES for explaining the print procedure in Example 4 herein;

[0113] Fig. 27 is a representative example of a screenshot of a Cura™ LulzBot™ 3.6.20 interface;

[0114] Fig. 28 is an example of several lines of G-Code employed in the software associated with printer used in Example 4 herein;

[0115] Fig. 29 is a top plan view and photographic image of the tubular item printed using the procedure in Example 4 herein showing an internal shell of reinforcing TPU (red) and an exterior shell of silicone (white);

[0116] Fig. 30 is a perspective view of the tubular item of Fig. 29.

[0117] Fig. 31 is front elevational representative view of a printing apparatus for use in a further embodiment of the methods herein for printing of a composition such as a composition including a thermoset silicone polymer through a first nozzle and printing a long reinforcing fiber with a second nozzle including a fiber cutting device;

[0118] Fig. 32 is a perspective view of the apparatus of Fig. 31;

[0119] Fig. 33 is a top perspective view of an assembly of a mounting arm, two printing mechanisms and a fiber cutting device used in the apparatus of Fig. 31;

[0120] Fig 34 is a bottom perspective view of the assembly of Fig. 33;

[0121] Fig. 35A is a top, front perspective view of a releasably attachable cutting device assembly;

[0122] Fig. 35B is a bottom, front perspective view of the cutting device assembly of Fig. 35A;

[0123] Fig. 35C is a top, rear perspective view of the cutting device assembly of Fig. 35A;

[0124] Fig. 35D is a bottom, rear perspective view of the cutting device assembly of Fig. 35A;

[0125] Fig. 35E is a side elevational view of the cutting device assembly of Fig. 35A;

[0126] Fig. 36 is a schematic perspective view of an embodiment of a cutting device for use in a cutting device assembly such as that of Figs. 35A-35E; [0127] Fig. 37 is an enlarged view of an interior portion of the apparatus of Fig. 31 in a portion of the long reinforcing fiber printing mechanism having a tube support, such as polytetrafluoroethylene (PTFE) tube support, for the continuous fiber passing through the long fiber printing mechanism to the printing nozzle thereof;

[0128] Fig. 37A is a front perspective view of the second nozzle shown in Fig. 37;

[0129] Fig. 37B is a front elevational view of the second nozzle shown in Fig. 37;

[0130] Fig. 37C is a rear elevational view of the second nozzle shown in Fig. 37; [0131] Fig. 37D is a rear perspective view of the second nozzle shown in Fig. 37;

[0132] Fig. 38 are photographic representations of printed composite specimens printed in Example 5 including (a) a printed composite of thermoset silicone in a parallel orientation to printed Kevlar® long reinforcing fiber; (b) a printed composite of thermoset silicone in a perpendicular orientation to printed Kevlar® long reinforcing fiber; (c) a printed composite of thermoset silicone in a parallel orientation to printed carbon long reinforcing fiber; and (d) a printed composite of thermoset silicone in perpendicular orientation to printed carbon long reinforcing fiber;

[0133] Fig. 38A are photographic representations of further printed composite specimens from Example 5 printed in (a) a perpendicular direction without a long reinforcing fiber; (b) a perpendicular direction with a long reinforcing fiber layer extending in a longitudinal direction; (c) a parallel direction without a long reinforcing fiber; and (d) a parallel direction with a layer of long reinforcing fiber extending also in a longitudinal direction;

[0134] Fig. 39 is a graphical representation showing the relationship of tensile stress against strain to illustrate the tensile strength of additive printed silicone material printed in a longitudinal direction in comparison with additive printed composites of silicone material printed in a longitudinal direction with and without a carbon fiber layer using samples as in Fig. 38A.

[0135] Fig. 40 is graphical representation showing the relationship of tensile stress against strain to illustrate the tensile strength of additive printed silicone material printed in a transverse direction in comparison with additive printed composites of carbon fiber and silicone material wherein the silicone material is printed in a transverse orientation and a layer of carbon fiber is printed in a longitudinal direction so that the carbon fiber has a perpendicular orientation to the silicone printed layer in the composite as in the samples of Fig. 38A.

[0136] Fig. 41 is photographic representation of a disc-shaped, carbon fiber-reinforced silicone composite part additively printed in Example 5 herein; [0137] Fig. 41A is a representative graphical representative of a design model for a curved, cylinder-shaped carbon fiber-reinforced silicone composite part for printing using the method and apparatus described herein;

[0138] Fig. 42B is a photographic representation of the top view of a curved, cylindershaped carbon fiber-reinforced silicone composite part additively printed using the design of Fig. 41 A in Example 5 herein;

[0139] Fig. 42C is a photographic representation of the left terminal end view of the composite part of Fig. 42B;

[0140] Fig. 42D is a photographic representation of the right terminal end view of the composite part of Fig. 42B;

[0141] Fig. 43 is a graphical representation of a stress v. strain curve of two samples each of additive printed slab composites of silicone and Kevlar® long reinforcing fiber in which the silicone is printed both perpendicular to and parallel to the long reinforcing fiber direction which extends longitudinally through the slabs;

[0142] Fig. 44 is a graphical representation of a stress v. strain curve of two samples each of additive printed slab composites of silicone and carbon long reinforcing fiber in which the silicone is printed both perpendicular to and parallel to the long reinforcing fiber direction which extends longitudinally through the slabs;

[0143] Fig. 45 is a schematic representation of a control circuit for the operation of the cutting device and control system for feeding the continuous long fiber;

[0144] Fig. 46 is a flow chart of printing operation steps for integrating the cutting device into the printing operation of the embodiments herein providing extruded long continuous fiber to forma composite article;

[0145] Fig. 47 is a graphical representation of apparent viscosity as a function of shear rate for various silicone materials in Samples A-C according to Example 6; and

Fig. 48 is a graphical representation of extrusion speed as a function of the pressure applied to the first pressurized nozzle according to Samples A-D in Example 6.

DETAILED DESCRIPTION OF THE INVENTION

[0146] The present invention includes methods and an apparatus for forming composite three-dimensional elastomer articles formed using additive manufacturing, including composites including a thermoset silicon-containing polymer. The composites may also include a reinforcing layer(s) of thermoplastic material.

[0147] In the description herein, words like “inner” and “outer,” “upwardly” and

“downwardly,” inwardly” and “outwardly,” “right” and “left,” “upper” and “lower,” “distal” and “proximal” and words of similar import refer to directions in the drawings for assisting in clarifying the features of the invention unless otherwise specified.

[0148] As used herein a “thermoset silicon-containing polymer” may be any of a variety of silicone homopolymers and co-polymers that are curable to form a silicone elastomer (also referred to as a silicone rubber). Silicones are generally polymers that incorporate at least silicon, oxygen and hydrogen in their chemical structure. Curable thermoset silicon- containing polymers (silicones) which may be used to form silicone elastomers include polymers having a backbone as classified by the Standard Rubber Nomenclature definitions provided by ASTM International in ASTM D 1418- 17 as VMQ (silicones), PVMQ (phenylsilicones) and FVMQ (fluorosilicones). However, silicones that are not readily classified by ASTM D 1418- 17 may also be used provided they demonstrate useful additive manufacturing printable characteristics as described herein.

[0149] “Curing” as used herein is meant to encompass any method of providing an elastomeric structure to a silicone by either vulcanization, chemical crosslinking, catalyzed cross-linking and the like. After curing, thermoset silicon-containing polymers (silicones) form silicone elastomers. An “elastomer” (also sometimes referred to as a rubber) as used herein is intended to mean a polymeric material that has viscoelastic properties, and that upon application of a stress will deform, but after removal of the stress, will recover a portion of its original form. The degree to which the material recovers its original form is an elastomer property typically measured through its “compression set” resistance (the percentage of the elastomer that is not recovered upon removal of stress, thus the lower the percentage of compression set resistance, the stronger the elastomeric recovery). Other elastomer properties typically measured include elongation at break, Young’s modulus, tensile modulus, viscosity, and other physical properties. Thermal behavior of elastomers and their cure system’s impact on such properties are also useful for evaluation of an elastomer for various end use applications.

[0150] In additive manufacturing, the thermal behavior, flowability and viscosity are all properties that must be evaluated as the silicone will behave differently depending on thermal properties, including its glass transition temperature (Tg), its speed of curing and its state of curing during printing. As most silicone elastomers are thermosetting in nature, they are more difficult to use in applications where thermoplastics are more readily useful and economically feasible. Thus, there is still a need in the art for methods for using silicone elastomers in additive printing that is addressed herein.

[0151] In an uncured state, a silicone is typically a liquid or an adhesive gel. Silicones for forming silicone rubber can be cured using a variety of curing systems, including catalyst cure systems, typically using a platinum-based catalyst, a condensation curing system, a peroxide cure system and an oxime cure system.

[0152] In platinum catalyst curing, crosslinks are formed using functional silicone polymers such as vinyl-functional silicones and hydride-functional silicones through addition reactions to form the crosslinks. Such reaction leaves no byproducts and so is a preferred pathway for curing in the art.

[0153] Condensation systems typically involve a crosslinking material that is activated in some manner. In a common one-part system, functional silicones are employed that when contacted with water at room temperature will undergo hydrolysis and the hydrolyzable groups (hydroxyl or silanol groups) will initiate the curing reaction. The hydrolysis reaction once initiated continues until curing is done, and can take place at room temperature. Crosslinking materials include for condensation systems including functional silanes having active oxygen containing groups such as alkoxy, acetoxy, ester, enoxy or oxime silanes, e.g., methyltrimethoxysilane, methyltriacetoxysilane and similar materials. Such substituted groups and/or functionalized groups can be catalyzed as well if desired using organometallic catalysts such as tetraalkoxytitanates, chelated titanates, tin catalysts (e.g., dibutyl tin dilaurate and acetoxy tin).

[0154] In a two-part condensation, the crosslinking material and any catalyst is retained in one container while the curable silicone polymer composition (absent those materials) is retained in a separate container. The curing is initiated upon mixing of the materials in the two containers.

[0155] Other silicone cure systems for forming silicone elastomers include peroxide cure systems that can crosslink through a reactive silicone site forming an Si-R-Si link between silicone chains.

[0156] Such systems are well known in the art, and any silicone that upon curing using such systems known or to be developed may be employed herein provided the curable material is able to exhibit Bingham plastic behavior during the additive manufacturing printing process. That is, the silicone must be flowable and the curing controlled through the speed, temperature and material properties to allow for the silicone to be flowable through the equipment to print layers in a timely manner before becoming too viscous to process. A Bingham plastic is a viscoplastic material that remains solid until a level of stress is applied and it becomes flowable as a viscous fluid. Such a material is an elastic solid at a shear stress, T, that is less than a critical value, To. Once the shear stress exceeds the critical shear stress, also referred to in the art as the “yield stress,” the material flows in such a way that the shear rate, du/dy, is directly proportional to the amount by which the applied shear stress exceeds the yield stress and the following equation applies:

[0157] If such properties are achievable by a curable silicone than such a silicone can be employed in an additive manufacturing method and also printed using the apparatus herein. Various silicone properties may exhibit such properties and/or can be modified, such as by use of additives, to exhibit desired Bingham plastic behavior.

[0158] Preferably the silicone polymers used herein are one or more of polysiloxanes, polyalkylsiloxanes, polydialkylsiloxanes, polyarylsiloxanes, polyaralkylsiloxanes, and blends, alloys or copolymers of these materials with each other or with thermoplastic materials as described herein. Further, such thermoset silicon-containing polymers may have one or more hydrogen or one or silicon-bonded bonded group(s) on the silicon atoms in the main chain substituted with one or more groups, each of which substituted groups may further be functionalized or further substituted. Such substituted or functional groups may be branched and/or straight chain groups, including but not limited to hydroxyl, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkenoxy, alkynoxy, aryloxy, arylalkyl, arylalkoxy, arylalkenoxy, vinyl, carboxyl, carbonyl, halogen, heterocyclic, and fluorinated or perfluorinated groups.

[0159] Compositions including silicone-containing polymers herein may include curatives, cure initiators, crosslinkers such as a hydrolytic crosslinker, cure catalysts such as an organic peroxide, and other cure system components as noted above and as are known in the art or to be developed. Additives and/or modifiers may further be incorporated into the composition including silicone containing polymer(s), such as, but not limited to, siloxane additives, ultra-high molecular weight siloxane additives, clarifiers, processing aids, stabilizers, thixotropic agents, rheological agents, compatibilizers, colorants such as pigments and dyes, fillers, such as carbon black, quartz, silica, pyrogenic silica, carbon nanotubes, glass fiber and optional coupling agents, aramid fiber, olefinic fibers, carbon fibers, UV absorbers, UV stabilizers, lubricants, such as waxes, fatty acids and other rheological additives, flame retardants, polyols, amides, fluoropolymers, fluorinated or perfluorinated polymer additives, nanosilica (i.e., nanosilicon dioxide) particles, polysiloxanes, antiblocking aids such as silica and talc, optical brighteners, dispersants, wetting agents, compatibilizers and any other suitable silicon-containing polymer additive and/or modifier known or to be developed for providing desired composition properties, provided such additive(s) do not block, prevent or substantially impede the ability to print the composition having a thermoset silicon-containing polymer by additive manufacturing. [0160] Preferred additives for use in a thermoset silicon-containing polymer composition herein curatives such as peroxide curatives, typically incorporated in about 0.5 to about 5.5 parts per 100 parts of the silicone polymer, or in other systems a platinum catalyst in an amount of about 0.0005 to about 0.0015 parts per 100 parts of silicon- containing polymer. Other preferred additives include colorants and pigments such as white (titanium oxide), yellow (iron oxide or azo), blue (phthalocyanine GS or ultramarine), and/or green (phthalocyanine BS) in amounts that may vary but typically individually up to about 1.0 parts per hundred parts silicon-containing polymer or collectively up to about 1.5 parts per 100 parts silicon-containing polymer.

[0161] Such additives, other than any specific cure system, such as rheological or thixotropic agents are optional and may be incorporated in amounts up to a total of about 50% by weight.

[0162] Depending on the cure system used, the degree of relevant curative may be adjusted for the system. As such cure systems are known in the art, the same systems may be used herein as noted above. Preferred examples of thermoset silicones for use within the invention include commercially available silicones such, for example, but not limited to two-part silicones with platinum cure systems, including the following materials available from Dow Chemicals: DowSilOSE 1700, Xiameter™ RBL 2004-50, Silastic™ 9200-50, Silastic™ 3D LC-3335 and Silastic™ 7-5860; Liveo™ C6-770 from DuPont; and AMSil™ 20501-50, and AMSil™ 20501-70 from Elkem, and one-part silicones with a peroxide cure system, such as AMS silicone type 3302H, available from Primetech® Silicones. Such systems may be used and combined as recommended by their manufacturers. Other silicones that meet similar criteria and capabilities may also be used herein. Without intending to limit the scope of the invention, preferred silicones for use herein that operate, for example, at a target extrusion speed of about 10 mm/s to about 100 mm/s, so as to have a high viscosity at a zero shear rate, for example, those having viscosities at zero shear rate of about 20,000 poise to about 100,000 poise and/or those having a low viscosity at a high shear rate, for example, those having viscosities of about 2,000 poise to about 18,000 poise at about 100/s to about 1,000/s, wherein high shear rate means a shear rate on silicone of about 100/s to about 1000/s. Such materials are also preferred that may exhibit Bingham plastic behavior as noted herein.

[0163] A thermoplastic composition herein includes at least one thermoplastic material(s) for use herein in one or more reinforcing layer may be any suitable thermoplastic capable of printing through additive manufacture, including but not limited to polyolefins including polyalkylenes such polypropylenes, polyethylenes, polybutylenes and polyethylene terephthalates, polyamides, polyesters, polyimides, polyarylene ethers, polystyrenes, polystyrene -butadiene, polyacrylonitriles, polyacrylonitrile-butadiene-styrene, polystyrene-acrylonitrile, polyphenylene sulfides, polyphenylene oxides, polyphenylene oxide blending with polystyrene, polyalkylene oxides and polyalkylene ethers, polyoxymethylenes, polyester polyols or polyalkylene polyols such as polyethylene terephthalate glycol, polyacrylates, polyalkylacrylates, polyvinyl acetates, polyvinylchorides, polyvinylidene chlorides, polyvinyl acetates, polyvinyl alcohols, polyacetals, polyvinyl ethers, polyvinylidene fluoride, melt-processible fluoropolymers (including FEP, PFA, ETFE), and polyarylene ethers, polyarylene ether ketones, polyarylene ether sulfones, and other aromatic polymers as described in co-pending U.S. Patent Application No. 16/568,125, thermoplastic elastomers (TPEs) and thermoplastic polyurethanes (TPUs). Suitable commercial thermoplastic polyurethanes include Ninjaflex® TPU, Cheetah® TPU, and Armadillo® TPU, each available from NinjaTek®. Suitable thermoplastic elastomers (TPEs) include Taulman® PCTPE (a plasticized copolyimide TPE), available from Taulman3D.com as well as polyether block amide (PEBAs) under the tradenames of Pebax®, available from Arkema or 3DXtech.com, and Vestamid® E, available from Evonik Industries. Fluorinated TPEs may also be used and are available from Solvay and Daikin Industries. Further, thermoplastic(s) as noted above, for use herein within a reinforcing layer, may include copolymers (made through random, block or graft polymerizations), alloys, blends and complex or cross-linked structures of these various thermoplastic materials, provided they are each capable of being processed through an additive manufacturing apparatus, and preferably also they are capable of providing reinforcement to a layer of a composition comprising a thermoset silicon- containing polymer as described above.

[0164] Such thermoplastic compositions may include one or more additives and/or modifiers, as are known in the art or to be developed for thermoplastic compositions, which may be incorporated into the composition for printing, including clarifiers, processing aids, stabilizers, colorants such as pigments and dyes, fillers, such as carbon black, silica, quartz, pyrogenic silica, nanosilica particles, glass fibers and optional coupling agents, aramid fibers, carbon fibers, whiskers, carbon nanotubes, UV absorbers, UV stabilizers, lubricants, such as waxes, fatty acids and other rheological additives, flame retardants, polyols, amides, fluoropolymers in micropowder form, fluorinated or perfluorinated polymer additives, antiblocking aids such as silica and talc, optical brighteners, tensile modifiers, surface modifiers, slip agents, dispersants, wetting agents, adhesion promoters, antistatic agents, antimicrobial agents, desiccants and other suitable thermoplastic additives known or to be developed, provided such additives and/or modifiers do not block, prevent or substantially impede the ability to print the thermoplastic composition by additive manufacturing. Such additives are optional and may be incorporated in varying amounts depending on the intended end properties of the composition, provided the compositions are still printable in an additive printer apparatus.

[0165] In one embodiment of a method herein, the first composition including a first thermoset silicon-containing polymer is provided, and a thermoplastic composition is provided which may be as described above. An at least partial layer of the first thermoset silicon-containing polymer is printed herein and in one embodiment herein, an at least partial layer of the thermoplastic composition is also printed. The layers are each preferably printed using an additive manufacturing device. As used herein, the term “layer” or “at least partial layer” include complete or partial deposition of a first thickness of a design layer in a computer design model (as the thickness may be set by the extruder nozzle tip or head) in an additive manufacturing apparatus, and may be a solid (complete) layer extending across the entire design width of the article in that particular layer, or only a partial layer. Partial layers are those that do not extend across the entire design width of the article, and may be, for example, a patterned layer that has a design, pattern or discontinuity across all or a portion of the design width of the article (which may or may not include more than one material), a partial layer of two different materials arranged within a single layer either in a patterned print as noted above or arranged so that the partial materials layers are in a juxtaposed side-by-side position with respect to each other over the entire design length or only a portion thereof.

[0166] As an example, a partial layer in a design pattern, e.g., a mesh design pattern or other design pattern or discontinuous layer may be incorporated as a reinforcing layer within the composite or a substantially complete layer may be formed as a reinforcing or other layer within the composite article. This enables localized layers of reinforcement points in an otherwise solid print layer and/or intermingling of multiple polymers printed independently as separately printed layers but that occur at the same level of z-direction depth in the article e.g., a mesh design pattern layer of a thermoplastic polymer and a fill layer of a thermoset silicon-containing polymer that may fill the openings in the mesh and/or overlay the openings also with a substantially complete layer of thermoset silicon- containing polymer). [0167] As another example, if printing a reinforced article of a circular cross-section, either a solid cylinder or tubular article with an opening extending therethrough, each printed layer may include more than one material of varying widths to form the circular shape. In the case of the tubular article, one or more gaps in printing in layers defining the opening would be left in printed layers that are partial layers, once a layer height is reached where the opening is to be defined that would include one or more of the materials, such as, for example, a partial layer print of the first thermoset silicon-containing polymer over a portion of the width of the article on outer portions of a layer, and, on inside portions of the width of such layer partial layer prints of a reinforcing composition including a thermoplastic material may be printed which are juxtaposed to the outer partial print layer leaving a central gap for defining the print of the opening. Thus a two layer composite with an opening may be printed by using complete layers and partial layers or leaving gaps to accommodate a design.

[0168] As used herein, when referring generally to the term “layer”, one skilled in the art would thus understand based on this disclosure and the applicant herein intends that use of the term “layer” includes fully complete, partial, or patterned and partial layers and may include one or more materials within a given layer (i.e., a first thickness of a design layer having a given design width and length within a computer design model), unless the layer is otherwise expressly described to be a particular type of layer. The term “at least partial layer” is intended to be used interchangeably with “layer” but is intended to clarify that some portion of the layer includes a material being printed and that material may be printed over some, most or all of the layer depending on the design.

[0169] The first composition including the first thermoset silicon-containing polymer and the thermoplastic composition in the invention are thus printed in one embodiment herein so as to each form layers that are at least partial layers so that they may be printed successively or within the same layer as noted above. In one embodiment, the first composition including the first thermoset silicon-containing polymer is printed first, and may be printed on a substrate. A reinforcing layer, that may be at least a partial layer or a complete layer, including the thermoplastic composition may be printed on the layer of the first composition including the first thermoset silicon-containing polymer or, may be printed in the same layer if each is only a partial layer. Such layers may be printed as noted above, or may be reversed, such that the thermoplastic composition is printed as a first at least partial layer, and the thermoset silicon-containing polymer composition is printed on a layer of the thermoplastic composition or within the same layer (as a partial layer) as the thermoplastic composition. However, as the thermoplastic composition is intended in the composites herein as primarily a reinforcement layer, in preferred embodiments herein, it is preferred that the thermoset silicon-containing polymer composition is printed in a first layer and the reinforcing agent is printed on the first layer.

[0170] In one embodiment, multiple layers (complete or partial) of the thermoset silicon-containing polymer composition may be printed on or as a first layer (wherein a first layer may in this case include multiple layers) prior to printing one or more reinforcing layer(s) of the thermoplastic composition. It is also possible in another embodiment herein, to print a layer of the thermoset silicon-containing polymer composition, a reinforcing layer of the thermoplastic composition and then one or more additional layers of the thermoplastic composition on top of the reinforcing layer. Thus, in varying embodiments herein, a layer of the composition including a thermoset silicon-containing polymer and a reinforcing layer including the thermoplastic composition may be layered as noted, layered in reverse, layered successively and in an alternating manner, or layered in alternating layers the each include within them successive layers of a single composition. Each of such layered printed structures forms a composite printed article having at least one printed layer of the thermoset silicon-containing polymer composition and at least one reinforcing layer including the thermoplastic composition. Each such layer within such structures may also include partial layers as noted above and other materials printed within the same layer.

[0171] The resulting composite articles may be used as-is after additive manufacturing in a layer-by-layer process to form a composite article. Such three-dimensionally printed composite articles may be used as-is as a new part formed as an alternative to directly compression molded-articles, or may be further heat treated by annealing, oven treatment, compression molding or other forming process know for plastic articles in the composite arts for strengthening or for other processing.

[0172] In addition, the three-dimensionally printed composite articles formed by additive manufacturing may be further used as feed or forming materials, e.g., they may be printed into the form of blocks, spheres or the like and/or further pelletized or ground into smaller articles, and such feed or forming materials may be the basis of forming a further shaped article through other heat molding techniques, such as to form rods, rings, or other three-dimensional objects. Used three-dimensionally printed articles or articles formed therefrom may further be recycled using recycling techniques known or to be developed such as drawn into filament for further use in subsequent additive manufacturing methods or in heat molding processes.

[0173] In further embodiments herein, a second composition comprising a second thermoset silicon-containing polymer may be introduced into the composites herein. Such a second composition can be printed on the first composition including the first thermoset silicon-containing polymer or on the at least one reinforcing layer, and may also be printed within one of the other layers as a partial layer, such as in a juxtaposed or patterned configuration. The reinforcing layers may also be distinct or partial if desired. For example, at least one first silicone-containing composition layer(s) may be formed, at least one first reinforcing layer(s) having a first thermoplastic may be printed on the first silicone- containing composition layer(s). Between those layers, on top of them or within them in a partial or patterned manner, a second composition having a second silicone polymer may be optionally printed. Optionally, also a further reinforcing layer having a second thermoplastic material may be printed between or in any or all of the above-mentioned layers. In one embodiment, the one or more additional at least partial layer(s) of the second composition having a second thermoset silicon-containing polymer, as well as the at least partial layer(s) of the first silicon-containing composition and the at least partial layer(s) of the first thermoplastic, are printed in accordance with a design patterned.

[0174] In such embodiments having the second composition having a second thermoset silicon-containing polymer, the second composition having the second thermoset silicon- containing polymer may have the same or a different thermoset silicon-containing polymer than the first composition containing the first thermoset silicon-containing polymer. Thus, the compositions may vary by additives, blending or addition of other polymers within the printed layer using the same thermoset silicon-containing primary polymer, so long as both compositions are flowable using the characteristics of a Bingham plastic and are able to be printed using an additive manufacturing apparatus. Alternatively, two different thermoset silicon-containing polymers may be used in the first and second thermoset silicon- containing polymer compositions, in addition to which the additives and/or modifiers or other polymers, if any, in the compositions may also be the same base composition or may be varied.

[0175] Similarly, there may be more than one type of thermoplastic used in a thermoplastic composition and there may be more than one thermoplastic composition in different reinforcing layers. Such composites may be varied by layers and compositions, provided that at least one layer of a first composition having at least one first thermoset silicon-containing polymer and at least one reinforcing layer including at least one thermoplastic composition are incorporated into the composite printed, whether such layers are complete over the full design length or partial and/or whether layers include one or more materials within the same design layer. [0176] Such further embodiments of the composite, as with the previous embodiments, may also be further processed post-printing or used in a printed article in the printed state. Further processing may include surface finishing, polishing, annealing or further heatmolding of the finished, printed three-dimensional article formed from the composites noted herein using an additive manufacturing apparatus. In such an apparatus, the composites are formed layer-by-layer using a computer design model as is known in the additive manufacturing art in which case, a three dimensional object and its pattern are preprogrammed into existing software installed on the three-dimensional printing apparatus or open source software designed for this purpose. However, as for such composites having multiple layers of different materials, for the multi-layer composites formed herein, a preferred apparatus has been further developed by applicants that be used having a capacity for multi-layer printing such that the composites may be made at a faster and more precise manner than with a standard additive manufacturing apparatus.

[0177] Figs. 1 and 1 A show views of a preferred embodiment of an additive manufacturing apparatus 100. Fig. 1 provides a schematic representation of the apparatus, and Fig. 1 A is a perspective view of an apparatus installed for formation of three- dimensional composite articles according to the present invention as described above. [0178] As shown, a gantry assembly 102 having a plurality of longitudinal frame members 104 on either side of the assembly 102 and transversely extending frame members 106 for supporting a nozzle assembly 114 slidable along one or both of the transversely extending frame members 106. The frame member 106 are connected on either end to a slidable members 118 which are slidable supports mounted on the longitudinal frame members 104 on either side of the assembly. A drive motor 116 is positioned on one of the sliding members 118 (as shown it is on the left hand side) in operative communication with a programmable controller 120 and a printer drive mechanism 132 that operates the nozzle assembly 114 and with an additive manufacturing printer 134.

[0179] A base support frame 108 that may be movable and/or in slidable engagement with a lower gantry member 138 is provided. The support frame 108 includes a slidably engaged platform 110 that can support a substrate 112 for receiving a three dimensional printed article. The platform 110 includes mounting posts 140 for stabilizing the position of the central surface 142 that supports the substrate 112.

[0180] The arrangement of the overall three dimensional printer can be found in most additive manufacturing apparatus and as shown includes a Lulzbot Workhorse Edition printer. Other suitable commercial printers that have these features may also be used within the scope of the invention. [0181] The nozzle assembly herein was developed by the applicants herein to function on a variety of commercially available three-dimensional printers in an additive manufacturing apparatus having a suitable sliding gantry such as that shown in Fig. 1 A. [0182] The nozzle assembly 114 includes a first nozzle 126 for printing a first composition including a thermoset silicon-containing polymer. The first nozzle 126 is preferably a pressurized nozzle and is in communication such as through tube 125 with a source of pressurization 124. The source of pressurization can be run through the controller 120 for adjustment of pressure while printing and pressurization may be provided by any acceptable pressurization source, such as pressurized gas, which may be pressurized air, or an inert gas such as nitrogen or another pressure source. The source of pressurization 124 can be a compressed cylinder or other in-line air or gas source. Preferably any such compressed air or gas source has a control valve and pressure relief valve as is known in the art.

[0183] The first nozzle 126 is mounted in a mounting arm 128 that is configured to support the first nozzle 126 while also extending away from the nozzle to support a second nozzle 130 situated proximate to the first nozzle 126, but independently and stably mounted to the mounting arm 128. Also situated on the mounting arm 128 is a printer drive mechanism 132 for operably introducing a thermoplastic polymer filament 123 into the second nozzle 130. The thermoplastic filament 123 may be introduced from a drive roller 122 and passes into the nozzle at a controlled speed by means of the printer drive mechanism 132.

[0184] The first nozzle as a pressurized nozzle may be operated such that the pressurization source 124 is operably connected to a high pressure extruder assembly 144 including as shown herein in Figs. 1-5 and 10-14. The high pressure extruder assembly 144 may include a high pressure piston 148 which as shown in Fig. 11 includes an extending piston feature 149 to compress flowable material which is slidably operable within a syringe barrel 146 of the first nozzle 126. The outlet of the nozzle 150 may include a nozzle extruder tip 154 for controlling the width of the extruded thermoset silicon-containing polymer for printing. The extruder assembly is in communication with a heat source. As shown, a heated band or collar 152 may be positioned around the nozzle end 156 of the nozzle 126. The heated band 152 is preferably in operative communication with the controller 120 for controlling the temperature of the nozzle end 156 or hot end of the nozzle. [0185] The second nozzle 130 may be any suitable additive manufacturing nozzle configured for printing a thermoplastic polymer through the nozzle opening 158 thereof. The second nozzle 130 is preferably also in operative communication with the controller for setting a suitable temperature for extruding the thermoplastic chosen and for setting a drive speed for the filament through the printer drive mechanism 132.

[0186] The controller is also preferably programmed by modifying the open source or commercial software available with the additive manufacturing device to have a computer design model that allows for alternative, successive or other mapping of different layers of polymer from one nozzle at a time.

[0187] As noted above, the first nozzle 126 may print a first at least partial or complete layer of an article, and the program may then engage a second nozzle 130 to print a full or partial layer on the first at least partial layer, and further layers, such as a third or further layers of either material may then be printed over the full or partial layer form the second nozzle 130 and so on according to a design pattern. The pattern, extent and width of a design layer and/or its thickness may be programmed into the computer design model to allow for use of the nozzles individually.

[0188] The mounting arm 128 as shown in Figs.1-14 is configured to have an extending support portion 160 that extends transversely from a support seat 162 configured to hold the pressurized first nozzle 126. The support seat 162 defines an opening 164 through which the lower nozzle portion 156 of the first nozzle may pass and beneath which the heated band 152 may be positioned. The extending support portion is configured to be sufficient to support the first nozzle 130 and the nozzle assembly 114 printer drive mechanism 132. The second nozzle 130 is shown as a heated extruder, such as a commercial extruder, Lulzbot Thermoplastic Extruder. Other similar commercial extruders capable of printing thermoplastics may also be used. The first nozzle 126 may be adapted as any suitable pressurized nozzle, and a suitable such nozzle is available commercially as a Nordson high pressure extruder.

[0189] The mounting arm may be mounted through fasteners extending through openings 166 on a rear portion thereof which may mount to transverse members 106 allowing for the nozzles to be moved side to side and lower and higher on the gantry assembly 102 of the apparatus 100. The base support frame may also be used for adjustment of the printing of the article.

[0190] Other robotic arms or gantry assemblies may be readily adapted to controllably position the dual mounted nozzles 126, 130. Further the mounting arm 128 may be extended transversely in rearward or forward direction to accommodate a third nozzle which may be the same as either of nozzles 126 or 130 as would be understood by one skilled in the art based on this disclosure within the scope of the invention by extending either the support portion 160 or forming a second pressurized nozzle seat such as support seat 162 on the mounting arm. It is also within the scope of the invention that a second nozzle assembly including a second mounting arm identical to that shown is controllably mounted on the same transverse members or on independently suspended and slidably operative transverse arms of the gantry assembly. Such a second nozzle assembly can enable a second composition containing a silicon polymer or a second thermoplastic polymer to be printed in the same configuration and in the same composite matrix if desired, provided that the computer design model is modified to accommodate such printing.

[0191] In yet a further embodiment herein a method and apparatus are provided for forming composite articles comprising thermoset silicon-containing polymer.

[0192] For embodiments herein in which a composition having a first and/or a second thermoset silicon-containing elastomer are used (i.e., a curable thermoset silicone) to be printed in a composite comprising continuous long reinforcing fiber in a silicone/long reinforcing fiber composite, it is preferred that the continuous long reinforcing fiber incorporates one or more of continuous: carbon fiber, glass fiber, boron fiber, alumina fiber, silicon carbide fiber, quartz fiber, and various organic or para-aromatic fibers such as aramid fiber (such as Kevlar®), polybenzoxazole (PBO) fiber, ultra-high molecular weight polyethylene fiber, polypropylene, polyethylene terephthalate, polyethylene, polyimide, polyarylesters, polyetherimide, and polyvinyl alcohol, and synthetic organic fibers such as rayon and polyacrylonitrile fibers, and natural and synthetic fiber blends. Natural fibers may also be employed alone, or together with other organic or synthetic fibers as noted above including keratin, flax, viscose, sisal, hemp and jute. It is preferred for tensile strength and preferred manufacturing composite properties, that carbon, aramid, glass or thermoplastic fibers are used, with carbon, aramid and glass particularly preferred. Such fibers may be provided as single fibers, fiber tows, braids, blends and hybrid fibers, however, it is preferred that the fibers are provided to the process as continuous fiber so as to be fed through a nozzle. Fibers may optionally include sizing, coatings or treatments or agents to enhance adhesion within the printed elastomer article. Fibers may also have a coextruded coating as discussed further herein.

[0193] As a continuous fiber is extrusion fed into the additive printing process, a cutting device is preferably employed as described below that is set to cut the continuous reinforcing fiber into programmed long fiber reinforcement lengths to provide unidirectional or bidirectional long fiber reinforcement to the additive printed composite. As used herein, a long fiber reinforcement within the printed composite may vary greatly depending on the printing process and size of the composite being printed. Fiber may be provided as individual fiber, including monofilament, or in bundles also known as tows. Preferably fibers are provided in fiber bundles, wherein a diameter of the long reinforcing fiber bundles, wherein the individual fibers therein have diameters of about 10 microns to about 50 microns and the bundles have a diameter of about 200 microns to 2 mm.

[0194] In the printed composite, it is preferred that the long fiber reinforcement in an at least partial layer within the printed composite makes up about 5% by volume or more, preferably about 10% to about 60% by volume, and may be up to about 99% by volume of the printed composite. It is preferred that the long fibers in the printed silicon/long fiber composite are about 5% to about 30% by volume of the composite, and most preferred that they are about 10% to about 20% by volume of the composite.

[0195] The long fiber used in the composite materials in this embodiment may be provided from a continuous fiber roll, chuck or other continuous fiber feeding device into the fiber extruder as described further herein below, or as a fabric or the like. In a preferred embodiment, the continuous long fiber is provided using a pinch roller that is electronically controlled by additive manufacturing apparatus. As used herein, continuous fibers when incorporated into the composite as long reinforcing fibers are cut to a particular length measured in the long dimension of the cut fiber which is generally greater than about 0.5 inches (1.27 cm) and up to a length of about 10 in. (25.4 cm), preferably about 1 in. (2.54 cm) to about 6 in. (15.24 cm). In larger printed composites, the size may be varied for larger structures, for example, those up to about 3 ft. (91.44 cm), however, the size of the structure and fibers are not intended to be limiting to the scope of the invention. A long fiber is generally a fiber that has a length to diameter ratio (ltd) of greater than about 100.

[0196] By varying the length when cutting the continuous reinforcing fiber fee, a variety of long reinforcing fibers may be laid into and printed into a thermoset silicon-containing polymer that is curable so that printed and then cured articles formed hereby create a long- fiber reinforced composite that can provide varying degrees of long fiber reinforcement either in the longitudinal direction of the composite or in a transverse direction in the composite depending on the printing design, and further the long reinforcing fiber may be laid into the composite in varying directions in the same or different layers, which layers, as noted above may be partial layers or complete layers. In addition, the thermoset silicon- containing polymer may be printed in layers in a direction that is parallel to or perpendicular to the direction of printing of the continuous fiber into long reinforcing fibers within the composite. These directions may also be varied and the layers varied as partial or complete layers to create varying designs of material and varied composite properties.

[0197] For example, in the method, one may print the at least partial layer of the first composition comprising the first thermoset silicon-containing polymer in a generally transverse direction and print the at least partial layer of the long reinforcing fibers in a second generally longitudinal direction. This pattern may also be reversed, where the first composition comprising the first thermoset silicon-containing polymer is printed in a generally longitudinal direction with the long reinforcing fibers being printed in a generally transverse direction.

[0198] The method for forming composite articles in the present embodiment includes providing a first composition including a first thermoset silicon-containing polymer. The thermoset silicon-containing polymer may be any of the curable silicon-containing polymers herein, including those identified above as being the most useful for holding composite three dimensional shape such as those that at a target extrusion speed of about 10 to about 100 mm/s that have a high viscosity at zero shear rate of about 20,000 poise to about 100,000 poise and/or those that have a low viscosity (about 2,000 poise to about 18,000 poise) at high shear rates of 100/s to about 1,000/s. The composition may include one or more of such silicon-containing polymers, and may further include any of the suggested additives and curatives as noted above, including agents to modify viscosity if needed or any suitable reinforcing fiber (such as chopped fiber and whiskers) provided such additives and reinforcing materials do not substantially impact the printing capability of the composition at the given printing conditions.

[0199] Preferred silicon-containing polymers noted above include at least one polymer selected from the group of a polysiloxane; a polyalkylsiloxane; a polydialkylsiloxane; and combinations, or co-polymers thereof. The first thermoset silicon-containing polymer may also comprise at least one functional group selected from the group consisting of hydroxyl, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkenoxy, alkynoxy, aryloxy, arylalkyl, arylalkoxy, arylalkenoxy, vinyl, carboxyl, carbonyl, halogen, heterocyclic, and fluorinated and perfluorinated groups thereof. The first composition comprising the first thermoset silicon- containing polymer may also comprise one or more components selected from the group consisting of a curative, a cure catalyst, an organic peroxide, a hydrolytic crosslinker, a siloxane additive, an ultra-high-molecular-weight siloxane additive, clarifiers, UV absorbers, optical brighteners, pigments, thixotropic agents, rheological agents, compatibilizers, colorants, stabilizers, flame-retardants, quartz, silica, pyrogenic silica, carbon black, fluorinated or perfluorinated polymer additives, and nanosilica dioxide particles.

[0200] The first composition provided is printed in an “at least partial layer,” as defined above, of the first composition having the first thermoset silicon-containing polymer. Such composition may be printed on a substrate or another layer of an existing composite. The substrate may be flat, curved or pre-shaped into a specific configuration. The layers may be at least partial or complete individual layers printed in one or more successive layers or in alternating layers with layers of the reinforcing fiber. Further, the first composition having the silicon-containing polymer and the long reinforcing fiber may be printed individually in partial layers that are overlapping or that are coextensive wherein both the first composition and the long reinforcing fibers are within a single layer according to a design layer, which layer may itself be partial or complete as defined above.

[0201] Printing of the first thermoset silicon-containing polymer preferably is done as noted above and as described for a further embodiment of an additive printing apparatus below, using a first nozzle of the additive manufacturing device that is preferably heated and that is also preferably suitable for pressurized printing of the silicon-containing polymer. [0202] As noted above, the method can include printing one or more additional at least partial layer(s) of the first composition having the first thermoset silicon-containing polymer on a first at least partial layer thereof before or after printing the at least partial layer of long reinforcing fibers, which may be printed also in additional at least partial long reinforcing fiber layers. It is possible to print these at least partial or complete layers successively and in an alternating or designed layering manner, printing one or more additional at least partial layers of the first composition having the silicon-containing polymer and one or more additional at least partial layers of the long reinforcing fibers comprising the thermoplastic composition on the at least one reinforcing layer. Such layers would each be printed according to a preferred design pattern and programmed to be controlled through the additive printing device.

[0203] After providing a continuous long reinforcing fiber(s), such fiber(s) is/are preferably printed using a second nozzle of the additive manufacturing device in an at least a partial layer on one or more of an at least partial layer of the first composition having the first thermoset silicon-containing polymer that were printed using a first nozzle of the additive manufacturing device. The second nozzle in this embodiment is a fiber extrusion nozzle as described further below. The at least partial layer of the first composition having the first thermoset silicon-containing polymer and the at least partial layer of long reinforcing fibers are thus printed through respective nozzles either to be within the same layer, successive or alternating design layers.

[0204] As the continuous long reinforcing fiber is printed, it is preferably cut into long continuous fiber as the fiber leaves the second nozzle using a fiber cutting device. As noted herein, the fiber length of the long reinforcing fiber can by printed to a desired length enabling a variety of reinforcing patterns and locations within the resulting printed composite. Further, printing the long reinforcing fiber using the second nozzle preferably also includes heating the second fiber extrusion nozzle.

[0205] In one embodiment, the long reinforcing fiber printed to the be within the composites herein is simultaneously co-extruded through the second nozzle with a composition that includes one or more extrudable polymeric materials over the long reinforcing fiber in the second nozzle. Thus, in such an embodiment, the second nozzle may be a coextrusion nozzle. Such nozzles are known in the art for providing coating continuous reinforcing fiber created in situ. Such co-extruded fibers having an extrudable polymeric material thereon, may be introduced in a coextrusion second nozzle for use in particular composites wherein a coated or protected fiber is desired for additional reinforcement within the matrix, to enhance interlayer adhesion or to provide better compatibility or strength between the fiber and the matrix of the thermoset silicon- containing polymer. The extrudable polymeric material in such an embodiment, may be a variety of thermoplastic or thermoset materials or may be a second composition comprising a second thermoset silicon-containing polymer. The second thermoset silicon-containing polymer may be the same or different from the first thermoset silicon-containing polymer as described herein. The extrudable polymeric material may also be a thermoplastic or thermoset polymer composition using any of the thermoplastic or thermosetting polymers listed above for use in forming a thermoplastic reinforcing layer in the previous embodiment, provided it is co-extrudable material for use in co-extrusion over a fiber in a co-extrusion extruder nozzle.

[0206] Examples of thermoplastic extrudable materials include at least one thermoplastic selected from, e.g., the group consisting of polyolefins, polyoxymethylene, polyamides, polyesters, polyimides, polyarylene ethers, polyarylene ether ketones, polyarylene ether sulfones, polyphenylene oxide blended with polystyrene, polyacrylonitrile-butadiene-styrene, polystyrene-acrylonitrile, polyacrylonitrile, polystyrene, polyethylene terephthalate, polyethylene terephthalate glycol, thermoplastic elastomers and thermoplastic polyurethanes, and copolymers, blends, alloys, and derivatives thereof. The composition comprising the extrudable polymeric material may comprise one or more reinforcing fibers, such as short or chopped fibers, nanotubes, carbon nanostructures or whiskers. Thermosetting polymeric materials are as noted above for using in a reinforcing layer. A second thermoset silicon-containing composition may be any of those thermoset- silicon containing polymers noted for use in the first thermoset-silicon-containing composition, including the same selection of additives, curatives and reinforcing fibers within the composition provided the resulting composition is co-extrudable over a continuously fed reinforcing fiber(s) and, preferably also provided it may be cut if desired while depositing the co-extruded polymer coated reinforcing fiber in an at least partial layer in the additively printed composite.

[0207] In a preferred embodiment herein, the reinforcing fiber is not coextruded but printed directly using a heated second nozzle that is a fiber extrusion heated extruder having a heated second nozzle. In any of the above-noted types of continuously fed and preferably chopped reinforcing fiber/silicon-containing polymer composite printing embodiments, the method may also include compression molding the resulting composite article formed by the method into a modified composite article.

[0208] The resulting articles may be three-dimensional composite article(s) formed from this embodiment of the method noted herein that have a composite structure including at least one of the at least partial layer(s) of the first composition having the thermoset silicon-containing polymer and at least one of the at least one partial layer(s) of the long reinforcing fiber(s). In one embodiment, it may also include at least partial layer(s) of a second or more thermoset silicon-containing polymer(s) as well as further types of continuously fed and cut-to-size reinforcing fiber(s) of one or more types noted herein. In addition, such continuous fiber(s) in layer form may be provided in a variety of types such as sized fiber, unsized fiber, dried fiber, pre-treated fiber or fiber co-extruded with an extrudable polymer material as noted above.

[0209] Such three-dimensional article(s) may be O-rings, seals, gaskets, medical devices, medical implants, or component parts of such devices and implants or any other items that may be additively printed including various other items as noted herein.

[0210] The method in this embodiment may also include providing a second composition having a second thermoset silicon-containing polymer; and printing an at least partial first layer of the second composition having the second thermoset silicon-containing polymer on the at least partial layer of the long reinforcing fibers using the additive manufacturing device or printing each of these layers in an alternating or sequential manner according to a design pattern. Such a second composition having a second thermoset silicon-containing polymer may be introduced by alternating its introduction through the same first nozzle used to introduce the first composition having the first thermoset silicon- containing polymer, by co-extruding the second composition having the second thermoset silicon-containing polymer material over the long reinforcing fiber (using a coextrusion nozzle as the second fiber extruding nozzle herein) and/or by introducing a third mounted nozzle dedicated to introducing the second composition including the second thermoset silicon-containing polymer. [0211] In such a method embodiment, the first at least partial layer of the second composition having the second thermoset silicon-containing polymer may be a complete layer or a partial layer, and the first thermoset silicon-containing polymer and the second thermoset silicon-containing polymer may be the same or different from one another. It may be useful to use the same polymer, for instance, in a co-extrusion embodiment to compatibilize or introduce fiber that may be otherwise more difficult to print and lay into the silicon-containing polymer matrix.

[0212] The method may further including repeating steps the various steps noted above according to a computer design model to form a three-dimensional or other article using an additive printing device, preferably the additive printing device noted herein.

[0213] The method may also include introducing into the silicone/long reinforcing composites formed herein a further thermoplastic reinforcing layer, by alternating a feed through the first nozzle, or using a third or fourth additional heated nozzle to create a composite of one or more at least partial layer(s) of thermoset silicon-containing polymer(s), one or more at least partial layer(s) of a thermoplastic reinforcing layer(s) and one or more partial layer(s) of a long reinforcing fiber(s) which may, if desired also incorporate a co-extruded layer thereon. Such thermoplastic reinforcing layer(s) may be as described above in the first embodiment herein.

[0214] The method may also include, using and following a designed pattern to print a composite article having one or more additional at least partial layers of the first composition having the first thermoset silicon-containing polymer and one or more additional at least partial layers of the long reinforcing fiber(s), as well as any optional at least partial layer(s) of a second composition of a second thermoset silicon-containing polymer, and any optional thermoplastic reinforcing layer(s) as well as optionally use of an at least partial layer of long reinforcing fiber(s) having coextrudable polymer material extruded thereon. The method includes repeating the various printing steps to form an article based on a computer design model.

[0215] In this embodiment of the composite having long reinforcing fiber printed therein, as with the previous embodiments, the articles formed may also be further processed post-printing or used in a printed article in the printed state. Further processing may include surface finishing, polishing, annealing or further heat-molding of the finished, printed three-dimensional article formed from the composites noted herein using an additive manufacturing apparatus.

[0216] In such an apparatus, the composites are formed layer-by-layer using a computer design model as is known in the additive manufacturing art in which case, a three dimensional object and its pattern are pre-programmed into existing software installed on the three-dimensional printing apparatus or open source software designed for this purpose. However, as for such composites having at least one layer of a thermoset silicon-containing polymer, and a layer of a reinforcing long fiber, and perhaps further layer(s) of the same or different materials, a further embodiment of a preferred apparatus has been developed by applicants that can be used and that has the capacity for multi-layer printing such that the long-fiber reinforced composites may be made at a faster and more precise manner than with a standard additive manufacturing apparatus.

[0217] In this embodiment incorporating long reinforcing fiber in a printed thermoset silicon-containing composite, a further embodiment, referred to herein as embodiment 200, of the additive manufacturing apparatus is described herein and shown in Figs 31-37D and 45. In this application, in embodiments 100 and 200, use of like reference numbers indicates an analogous part or component. For example, reference number 126 is intended to refer to the first nozzle in the first embodiment 100 of the additive manufacturing device/apparatus described herein and reference number 226 is intended to refer to the first nozzle in the second additive manufacturing device/apparatus of the second embodiment 200. While the two nozzles need not be identical, to the extent they are analogous items, they have analogous reference numbers. To the extent the element is different in a matter material to the embodiment, a new number is provided or the difference described herein. However, as many of the elements in each of embodiment 100 and 200 may be created using different brands or types of component elements, some of which are commercially available, variations and modifications of the components as shown, unless noted to be limited, are within the scope and spirt of the invention.

[0218] Figs. 31 and 32A show a front elevational view and a top front perspective view, respectively of a preferred embodiment of an additive manufacturing apparatus 200 for use in printing a composite having a thermoset silicon-containing polymer and a long reinforcing fiber therein. Fig. 31 provides a schematic representation of the apparatus as installed for formation of three-dimensional composite articles according to the embodiment of the invention using a long reinforcing fiber as described above.

[0219] As shown, a gantry assembly 202 having a plurality of longitudinal frame members 204 on either side of the assembly 202 and transversely extending frame members 206, and a support drive pulley mechanism 207 for supporting and operating a nozzle assembly 214 slidable along one or both of the transversely extending frame members 206. The frame members 206 are connected on either end to a slidable members 218 which are slidable supports mounted on the longitudinal frame members 204 on either side of the assembly. A drive motor 216 is positioned on one of the sliding members 218 (as shown it is on the left hand side) in operative communication with a programmable controller 220 and a printer drive mechanism 232 that operates the second nozzle 230 in nozzle assembly 214, and with an additive manufacturing printer 234.

[0220] A base support frame 208 that may be movable and/or in slidable engagement with a lower gantry member 238 is provided. The support frame 208 includes a slidably engaged platform 210 that can support a substrate 212 for receiving a three dimensional printed article. The substrate may have an upper friction surface, carrier sheet or release sheet over the underlying substrate surface, each of which is optional, or be open substrate surface as shown in embodiment 200 in Figs. 31-37D and 45. Such an additional surface is optional in both embodiments. The platform 210 includes mounting posts 240 for stabilizing the position of the substrate 212.

[0221] The arrangement of the overall three dimensional printer can be found in most additive manufacturing apparatus and as shown includes a Lulzbot TAZ 5 printer having a Lulzbot TAZ Dual Extruder Tool Heat vl as a printhead (available from Aleph Objects, Inc. Loveland, CO). Other suitable commercial printers that have these features may also be used within the scope of the invention.

[0222] The nozzle assembly herein was developed by the applicants herein to function on a variety of commercially available three-dimensional printers in an additive manufacturing apparatus having a suitable sliding gantry such as that shown in Fig. 31 and 32.

[0223] The nozzle assembly 214 includes a first nozzle 226 for printing a first composition including a thermoset silicon-containing polymer. The first nozzle 226 is preferably a pressurized nozzle and is in communication such as through tube 225 with a source of pressurization 224. The source of pressurization can be run through the controller 220 for adjustment of pressure while printing and pressurization may be provided by any acceptable pressurization source, such as pressurized gas, which may be pressurized air, or an inert gas such as nitrogen or another pressure source. The source of pressurization 224 can be a compressed cylinder or other in-line air or gas source. Preferably any such compressed air or gas source has a control valve and pressure relief valve as is known in the art.

[0224] The first nozzle 226 is mounted in a mounting arm 228 that is configured differently from the mounting arm 128 of first embodiment in that it is supporting a different second nozzle configuration than that of the first embodiment. The mounting arm 228 of embodiment 200 is configured to support the first nozzle 226 (which may be the same as that of the first nozzle 126 of the first embodiment 100), while also extending rearwardly from the first nozzle 126 to support a second nozzle 230 situated proximate to the first nozzle 226, but independently and stably mounted on and to the mounting arm 228. Also situated on the mounting arm 228 is a printer drive mechanism 232 for operably introducing a reinforcing fiber 233 into the second nozzle 230. As best shown in Figs. 37A- D, a reinforcing fiber 233 may be supported by a nozzle inlet opening support 235 having a seated support tube 237 to support the entering reinforcing fiber 233 as it enters the second nozzle 230. In a preferred embodiment, the support tube 237 may be made of a variety of preferably inert materials that do not bind to or otherwise impact the passing reinforcing fiber 233, for example, polytetrafluoroethylene (PTFE) or a similar molded copolymer thereof, such as a copolymer of tetrafluoroethylene and perfluoralkylvinyl ether, or a copolymer of tetrafluoro ethylene and hexafluoropropylene, or other comparable material that introduces little or no frictional resistance and does not react to or create a significant impact on feed rate of the extruded reinforcing fiber or cause significant adhesion or damage to the fiber.

[0225] The continuous reinforcing fiber 223 may be introduced from a pinch motor feed mechanism including drive motor 232. However, any suitable, stable and preferably programmable feed mechanism may be used.

[0226] The first nozzle 226 as a pressurized nozzle may be operated such that the pressurization source 224 is operably connected to a high pressure extruder assembly 244. The interior of this assembly 244 is the same as that of high pressure assembly 144 in embodiment 100 and so may be shown with reference to Figs. 1-5 and 10-14. The high pressure extruder assembly 244 may include the same high pressure piston 148 which as shown in Fig. 11 that includes an extending piston feature 149 to compress flowable material which is slidably operable within a syringe barrel 146 of the first nozzle 126, and would operate in the same manner in the first nozzle 226. As shown in Figs. 33 and 34, the outlet 250 of the nozzle 226 may include a nozzle extruder tip 254 for controlling the width of the extruded thermoset silicon-containing polymer for printing. A silicon-containing polymer composition is fed into the nozzle as in a flowable form or paste and is extruded under pressure and heated for printing a silicone composition.

[0227] The extruder assembly 244 is in communication with a heat source. As shown, a heated band or collar 252 may be positioned around the nozzle end 256 of the nozzle 226. The heated band 252 is preferably in operative communication with the controller 220 for controlling the temperature of the nozzle end 256 or hot end of the nozzle. [0228] The second nozzle 230 may be any suitable fiber extruding nozzle useful for extruding a long reinforcing fiber and configured for printing such a fiber through the nozzle opening 258 thereof. The second nozzle 230 is preferably also in operative communication with the controller 220 for setting a suitable temperature for extruding the reinforcing fiber 233 chosen and for setting a drive speed for the fiber that operates also in a preferred embodiment herein in operable correlation with a cutting device 270 and that incorporates a printer drive mechanism 232 which includes a drive motor to operate the continuous fiber feed to the second nozzle in a controlled manner.

[0229] The controller 220 is also preferably programmed by modifying the open source or commercial software available with the additive manufacturing device to have a computer design model that allows for alternative, successive or other mapping of different layers of thermoset polymer from one nozzle and reinforcing fiber from the second nozzle whether delivered subsequently or simultaneously.

[0230] As noted above, the first nozzle 226 may print a first at least partial or complete layer of an article, and the program may then engage a second nozzle 230 to print a full or partial layer of reinforcing fiber on the first at least partial layer, and further layers, such as a third or further layers of either material may then be printed over the full or partial layer from the second nozzle 230 and so on according to a design pattern. The pattern, extent and width of a design layer and/or its thickness may be programmed into the computer design model to allow for use of the nozzles individually.

[0231] The mounting arm 228 as shown in Figs. 31-37D is configured to have an extending support portion 260 that extends longitudinally to from a support seat 262 configured to hold the pressurized first nozzle 226. The support seat 262 defines an opening 264 through which the lower nozzle portion 256 of the first nozzle may pass and beneath which the heated band 252 may be positioned. The extending support portion is configured to be sufficient to support the first nozzle 226 and the nozzle assembly 214 as well as the second nozzle 230 which is positioned in a rearward portion 231 including the printer drive mechanism 232 attached as a pinch motor as shown. The second nozzle 230 is shown as a reinforcing fiber extruder, such as a commercial extruder available, for example, from Markforged™. A lower portion 239 of the second nozzle 230 is preferably also heated. As shown the heated lower portion 239 may also have a heated band or a commercial hot end, such as an E3D V6 hotend may be used. The second nozzle 230 may also have a nozzle tip 258 for extruding the heated continuous reinforcing fiber. Other similar commercial continuous fiber extruders capable of printing or laying down a continuous reinforcing fiber may also be used, including such extruders as may include a reservoir for an extrudable polymeric material (or are capable of receiving such a material from an external source) and a coextrusion pathway for enabling an extrudable polymeric material to pass through the nozzle tip 258 around the continuous fiber.

[0232] The first nozzle 226 may be adapted as any suitable pressurized nozzle, and a suitable such nozzle is available commercially as a HPx Nordson high pressure extruder available from Nordson EFD, Westlake, OH, and using a high precision controller, such as an Ultimus V, also available from Nordson EFD. However, any suitable extruder that can capably extrude a composition including a thermoset silicon-containing polymer may be used with comparable capability.

[0233] The mounting arm 228 may be mounted through fasteners extending through openings 266 on a portion thereof which may mount to transverse members 206 directly or indirectly allowing for the nozzles to be moved side to side and lower and higher on the gantry assembly 202 of the apparatus 200. The base support frame may also be used for adjustment of the printing of an article.

[0234] Other robotic arms or gantry assemblies may be readily adapted to controllably position the dual mounted nozzles 226, 230. Further the mounting arm 228 may be extended transversely or in rearward or forward directions to accommodate a third nozzle (not shown) but which may be of the same configuration as either of nozzles 226 or 230 or nozzles 126 or 130 of embodiment 100 as would be understood by one skilled in the art based on this disclosure within the scope of the invention by extending either the support portion 260 or forming a second pressurized nozzle seat such as support seat 262 on the mounting arm. It is also within the scope of the invention that a second nozzle assembly including a second mounting arm identical to that shown may be controllably mounted on the same transverse members or on independently suspended and slidably operative transverse arms of the gantry assembly. Such a second nozzle assembly can enable a second composition containing an optional second silicon polymer, an optional a thermoplastic polymer or an optional second reinforcing fiber(s) to be printed in the same configuration and in the same composite matrix if desired, provided that the computer design model is modified to accommodate such printing.

[0235] The mounting arm 228, as shown in Figs. 33-36 includes in a preferred embodiment herein a portion 241 having fasteners 243 for receiving an extended mounting arm portion in the form of a support seat 245 for an optional cutting device 247. The cutting device as shown is a modified commercial cutting device having a motor 249, such as a servo motor or similar device, such as, for example a NEMA 17 stepper motor having a motor drive module, for operating the cutting device 247, an optional solenoid 251 or other pneumatic device for operating the cutter 253 that is positioned on an underside of the cutting device 247. A cutting frame for the device with operable motion arms 255 which are actuated and moveable by the motor having a stepper drive module for positioning the cutting device in operation and controllable by controller 220 or a separate controller. Preferably, it may be controlled by the controller of the printer, e.g., the RAMBo 1.3 Board for a LulzBot TAZ 5 printer.

[0236] The solenoid 251 or a similar pneumatic or mechanical device may similarly be driven by the controller for the stepper motor or an alternate controller to operate the opening and closing operation of the cutter 253 so that the cutting steps are moved into place as reinforcing fiber leaves the fiber extruder nozzle 230 and before printing or laying down of the fiber on a printed thermoset silicon-containing polymer layer. A graphical circuit representation of this control arrangement is shown in Fig. 45.

[0237] The cutting device may also include various spring-loaded support frame arms 257 for supporting and positioning the device in operable position against the rear of the mounting arm 228 as best shown in Figs. 33-35. As shown in Fig. 36, such frame arms may have a somewhat different configuration such as using an ABS clamping frame 257’ with an alternate spring locking mechanism 259’ to mount the frame on a fiber extruder. The solenoid 251 may have a limiter 261 ’ as shown in Fig. 36. The embodiment of a cutting device 247 in Fig. 36 also includes an optional arm clamp 263’ and corner spacers 265’. It will be understood that a variety of cutting devices may be used for cutting the reinforcing fiber 233 as it is extruded from the second nozzle 230. Commercial cutting devices may be used or modified to be controllable and mounted to the rear of the mounting arm or in tandem or other arrangement provided the cutter 253 is positioned to controllab ly cut the fiber at a given size and rate of motor speed as controlled by the printing software to work in correlation to the first and second nozzles 226, 230. Examples include but are not limited to (i) a rotational cutting blade devices having a hear motor, synchronous belt transmission, and a mounted cutting blade; (ii) a rotating cutting cylinder mechanism; (iii) a dual roller head cutting mechanism; (iv) an extending, piston operated cutting blade and the like. Any such cutting device may be used, but must be securely mounted and positioned in a controllably operable manner to correlate with the nozzle operation as programmed in the additive manufacturing device.

[0238] Each of the first and the second nozzles 226, 230 are preferably operably programmed in the computer design model to print an at least partial layer in a design pattern. If employed, the optional cutting device is similarly operated to work in tandem with the operation of the nozzles 226 and/or 230. The first and the second nozzles are preferably both operably programmed in the computer design model to print at least partial layers of the first composition and of the long reinforcing fiber in the design pattern.

[0239] The apparatus may be configured such that the first composition, preferably the first thermoset silicon-containing polymer, may be provided in the form of a filament. The first nozzle and the second nozzle may be part of a nozzle assembly that further includes a mounting arm as described above to stably hold the first nozzle and the second nozzle in position for tandem operation. The mounting arm and its support base for supporting the first and the second nozzle is preferably operably and releasably connectable to the fiber cutting device, wherein the support base may further have respective openings therethrough to support the first nozzle and the second nozzle. If the cutting device is used, as shown in Figs. 33-36, the cutting device seat, instead of or in addition to the mounting arm 228 may include mounting holes and fasteners for connecting the cutting device seat to the gantry frame members.

[0240] The first nozzle 226 as noted above is preferably a high pressure piston extruder which is preferably in communication with a pressurized source and also controllable using the controller noted herein.

[0241] The first nozzle 226 preferably includes a nozzle end portion as noted above having a heating band or other heating device adapted to be positioned around the nozzle end portion 256 for heating a composition having a thermoset silicon-containing polymer as it is printed by the nozzle. The second nozzle 230 is preferably a long reinforcing fiber extruder as described above. The second nozzle 230 may also be configured to receive, in one embodiment hereof, an extrudable polymeric material that may be optionally coextruded over the long reinforcing fiber within the nozzle.

[0242] The fiber cutting device 247 is preferably operable to continuously cut long reinforcing fiber at a controlled interval length, which is determined at least in part by the desired printing speed and time for laying down various layers in the printed composite, while printing the at least partial layer of long reinforcing fiber. The second nozzle 230 may have a nozzle end portion 239 and a heating band or, as shown, a hot end that is adapted to be positioned around the nozzle end portion for heating the long reinforcing fiber. As shown in preferred embodiments, illustrated in Fig. 45, the fiber printing may be controlled and programmed to cut at a certain rate and timing depending on print speed of the silicone and fiber cutting and printing lay down of the long reinforcing fibers. In a first step 301, using the preferred apparatus as shown in Figs. 31-36, the entire printhead (second nozzle) is lifted up a sufficient distance to enable space for the cutting device cutter to advance. In step 302, the cutting device is rotated downward to be located in a manner that the cutting blade is located beneath the second nozzle 230 introducing the continuous long reinforcing fiber. In step 303, the cutting blades are activated and cut the fiber at a programmed length. The cutting device in step 304 is rotated back to its initial position behind the second nozzle printhead. In step 305, the printhead is then lowered again to continue to print the fiber and/or the silicone according to the programmed design.

[0243] It is further understood that it is within the scope of the apparatus as shown that the filament fed to the second nozzle may be changed in between layers to a second thermoplastic composition and the thermoset silicon-containing polymer composition in the first nozzle may be changed to a second thermoset silicon-containing polymer composition in the same nozzle to also accommodate printing more than two compositions in the same composite structure.

EXAMPLES

[0244] Example 1 : Printing Method

[0245] With reference to Fig. 15, a basic printing method is outlined that was adapted for use in the Examples herein. In a first printing step 168 involved slicing the file in Lulzbot Cura software for use with a Lulzbot additive manufacturing printer adapted to have preferred features as noted above, including a first nozzle for printing a thermoset silicon- containing polymer composition and a second nozzle for printing a thermoplastic composition reinforcing layer, each mounted on a mounting arm as described further below. The slicing involved a custom design model that took into account the offset of the two nozzle extruders which was calculated and the settings input into the slicing software using slicing techniques known to those of ordinary skill in the art. The code was post-processed for each material. In a second step 170, a GCode (machine code) was generated for each layer of the print for each of two compositions being printed to form a composite article.

[0246] In a further step 172, the GCode was loaded onto a memory card and inserted into the additive manufacturing apparatus.

[0247] A silicone composition was prepared for printing using DowSil™ SE 1700 with a platinum catalyst curable silicone. A first two-part thermoset DowSil™ SE 1700 silicon was prepared as follows. In a 500 ml plastic jar, 136.4 g of Part A DowSil™ SE 1700 (10 parts) and 13.6 g of Part B (1 part) DowSil™ SE 1700 were added. The combined parts A and B mixture were thoroughly mixed until uniform appearance was achieved to avoid an incomplete cure. The uniformity was checked by the absence of light-colored streaks or marbling after thorough mixing. After verifying the uniformity of the mixture, it was deaired in a vacuum oven using 28-30 in. Hg vacuum at room temperature to remove air bubbles. Then the mixtures was used for additive printing as described below as the silicone composition.

[0248] In a step 174, a silicone composition as noted above was loaded into the syringe barrel of a high-pressure dispensing tool by Nordson EFD mounted in a nozzle assembly according to the present invention, and a thermoplastic polyamide, nylon, sold as Lulzbot Taulman 618 Nylon, at 3 mm diameter (white) was loaded into a Lulzbot extruder mounted on the mounting arm of the nozzle assembly. As the filament absorbs water, the plastic is periodically run through drying cycles at 110 °C. The dispensing tips for the Nordson extruder were metallic tips with PTFE lining which provide a smooth surface and allow material to flow readily through the nozzle. A heating band as described above was attached to the Nordson nozzle extruder and a sensor was provided to control the temperature, which is preferably set at about 80°C to about 100°C for high viscosity silicones. The pressure fed to the piston mechanism of the Nordson nozzle was controlled by the Ultimus V Precision Dispenser which was in operable communication with and wired to the main controller’s board on the Lulzbot Workhorse 3D printer apparatus.

[0249] The nozzle assembly allowed the two extruders to move in tandem. The mounting arm was designed to minimize the amount of movement of the nozzles from vibration as well as to ensure the equipment cleared all parts of the additive manufacturing printer on which the nozzle assembly including the mounting arm was installed. The mounting arm used was as shown in the drawings herein.

[0250] The Nordson piston extruder is rated to produce up to 400 psi of extrusion force. The additive manufacturing device (a Lulzbot Workhorse Edition printer) was operated to print with the controller and code allowing for the automatic printing of composite sample parts formed incorporating both materials. The printer used is a fused filament fabrication (FFF) 3D printer by Aleph Objects. The printer was chosen for its large build volume and integrated calibration system.

[0251] The printer controller was able to turn the pressure and flow of material on and off by changing the state of the FAN 0. This allows the printer apparatus to print both materials from the two separate nozzles without human interaction. This implementation was directly integrated into the slicing software so that code generation was done automatically. The Cura slicing software was initially developed by Ultimaker and modified by Aleph Objects to work with the Lulzbot line of additive manufacturing printers. The Lulzbot Cura was the main slicing software used herein to prepare the composite parts made. [0252] An optional step 176 is optionally employed for thermoset silicone which may require additional thermal cycles (such as post-cure or annealing) to fully set the material. [0253] The same procedure was also carried out using a thermoset AMS 3302H silicone that is peroxide curable. The silicone was prepared and in a 10 mL high-pressure Nordson dispensing syringe, 8 g of Primetech AMS 3302H was loaded and compressed by hand to expel most of the air pockets. The syringe was then placed into the high pressure Nordson syringe booster. The syringe band heater was slowly heated to the desired temperature for silicone extrusion (80-110 °C), and the printing was commenced with the temperature and flow of the silicone reached a steady state.

[0254] Example 2: Silicone and Thermoplastic Fiber Composite Materials

[0255] To evaluate suitable curable thermoset silicon-containing polymers for forming silicones for use in the present invention, several commercial silicone materials were evaluated based on their rheological properties including their apparent shear viscosity (in Pa-s) and apparent shear rate (/s) at varying temperatures. Initial tests using as an example, PrimeTech™ AMS3302H commercially available silicone at 100°F, 150°F, 200°F, 250°F and at room temperature provided capillary rheometer data as shown, e.g., in Fig. 20 and were also evaluated using moving die rheometer data. This allowed for identification of a suitable temperature range and shear rate to achieve a desired viscosity range for printing of that material. Similar tests may be run for varying silicones to select operating parameters for printing.

[0256] Using those parameters and the process noted above in Example 1, a sample composite article in the form of a reinforced elastomeric tube was formed including a silicone layers and a polyethylene terephthalate reinforcing layer. The article is shown in Fig. 21. The article was analyzed using SEM imaging and the scans are shown in Fig. 21 A. The layer thicknesses were measured each at four points and the average layer thicknesses are provided below in Table 1.

TABLE 1

[0257] A test developed by applicant for measuring interlayer adhesion was employed to test the sample material and a test machine is shown in schematic form in Fig. 22 and perspective view of the machine is shown in Fig. 22A. In the test, a four-layer composite was printed as noted above, as a flat layer composite and the sample cut on one end to separate layers 1 and 2 from layers 3 and 4. A fixed lower seat stably holds layers 3 and 4 while a moving jaw lifts and is pulled by a machine applying a IkN load cell. The grip separation is 3 inches and the test rate is 10 in/min. The test specimen was placed in the grips so that there was minimum tension on the specimen. The test started and the grips were separated at a rate of 10 in/min until the specimen began to peel apart. The maximum load was recorded and the load was plotted against the extension.

[0258] Other tests that may be used to evaluate the samples include an Instron pull test using a Type A tensile bar according to ASTM D412.

[0259] Photographic representations of complex three dimensional printed composite articles formed using nylon 6,6 as a reinforcing material with silicone include O-rings and gaskets as shown photographically in Fig. 24A and formed using nylon 6,6 and silicone layer.

[0260] Example 3: Additive Manufacturing Printed Composites of Silicone with a Nylon 6,6 Reinforcing Design Layer

[0261] Figs. 23A and 23B show silicone layers printed on varying thermoplastic nylon 6,6 structures printed according to a design pattern. In this particular example, the design pattern provided a mesh design. In Fig. 23 A, a 0-20-340 mesh was printed as a reinforcing layer and in Fig. 23B, a triangle mesh was printed. Three layer structures with two silicone layers surrounding the mesh design layer are shown, and were printed and compared to a three layer composite formed by compression molding silicone layers and a polyethylene terephthalate reinforcing layer. A further test was run to compare the three layer structure with the four layer structure formed with the same materials but as described above in Example 2. The results are shown below in Table 2.

TABLE 2

[0262] Various composite parts were prepared using the nozzle assembly and apparatus herein and using a silicone polymer and mesh reinforcement layer. Fig. 16 shows a Nittany Lion Penn State logo pattern composite using a layer of nylon mesh under a layer of silicone and each was consistent to form the complex shaped article.

[0263] Fig. 17 shows a composite printing in process with a layer of silicone having a nylon 6.6 mesh reinforcement layer, with a partial silicone layer printed on top of the mesh layer.

[0264] Fig. 18 shows a finished square composite print with a nylon 6,6 mesh layer printed mesh layer visible through silicone layers.

[0265] Fig. 19 shows an interface of silicone and acrylonitrile-butadiene-styrene (ABS) in a part in which the silicone print can be seen as white as well as the black print of ABS. [0266] In each of the composite articles printed, a polytetrafluoroethylene covered steelbased baking sheets. The non-stick surface was used to ensure silicone-based composites made could be cleanly removed after thermal cycling and the steel enabled the surface to withstand the thermal cycles without melting. When new tips were provided, a calibration was carried out to determine the settings that would work best for printing speed and resolution desired. Travel speed for the high pressure extruder nozzle is directly related to the length of the material extruded out of the nozzle tip per time interval (z.e., mm/s). Layer height was adjusted to be 10% less than the inner diameter of the nozzle opening so that the layers had the opportunity to merge together. These settings can be incorporated into the slicing software.

[0267] Example 4: Tubular Structure Three-Dimensional Additive Printing Using Thermoset Silicone and Thermoplastic Reinforcement

[0268] This Example was prepared to describe the workflow and machine process for the additive printing of a silicone (in this case a Primetech™ AMS3302H silicone) and a thermoplastic reinforcement using as an example a thermoplastic polyurethane (TPU) in a tubular structure (i.e., in a structure containing both complete and partial layers to define an opening therethrough). The tube design used was made in accordance with development of multi-material tube shapes within a requested design envelope.

[0269] Tube shapes are modeled in a variety of computer aided design (CAD) software, such as AutoCAD® or AutoCAD® LT software, as well as SolidWorks® by Dessault Systems and Fusion 360® by Autodesk. Fig. 25 herein shows a screen capture of a three dimensional model from SolidWorks®. [0270] Once a series of three-dimensional models is completed in the CAD software package, the shapes are exported to a .STL file format. Such .STL file format is known as a surface tessellation language that simplifies the complex mathematical curvatures of the three-dimensional model into flat triangular shapes to reduce the complexity and computational power needed to perform the tool path design for three-dimensional printing. For multi-material printing, it is known to export the differing material shapes as separate .STL fdes to be designated in the print set-up software.

[0271] Fig. 26 is an Internet (Wikipedia) example of an .STL format file showing he differences between a curved model identified as CM and an exported .STL model identified as ES.

[0272] After the .STL models are ready, the printing plater and parameters are set up. The software used in this Example was Cura™ LulzBot™ edition 3.5.20. Cura™ (by Ultimaker) is an open-source universal print set up interface. The base printer (from Aleph Objects) used was provided also with a complimentary software print set up version of Cura™. This is the LulzBot™ edition of Cura™.

[0273] In this software, the .STL files are arranged in the digital build volume, given a specific nozzle to be printed with, and parameters are set for the process. The parameters vary based on the shape and the materials to be used. Some parameters including speed, extrusion temperature, and layer height. In Cura™, there are over 100 parameters that may be used to control the toolpath, i.e., the motion and direction, of the printer. Fig. 27 shows an example of a Cura™ LulzBot™ 3.6.20 interface.

[0274] When all parameters were set, the STL model was “sliced,” meaning the internal calculations were done to convert a three-dimensional STL model int a series of two- dimensional layers that are stacked to represent the three-dimensional model for printing. These two-dimensional layers are parsed into line-by-line coordinate machine code, known as G-Code. This code serves as the instructions directing motors to turn to specific angles at specific times to mode the nozzles around in three-dimensional space. The machine is able to extrude enough material out of both nozzles to product a close representation of the three- dimensional model using thousands of precise moves. Fig. 28 includes an example of a few lines of G-Code.

[0275] The combination of a three-dimensional model, printing parameters, and well- tuned hardware reliably produces desired shapes. For the tube shape shown in Fig. 25, the part was printed with two .STL files that were nested inside each other on the build plate. As the nozzles deposit material at independent speeds, temperatures and shapes, each layer may include silicone, thermoplastic or combinations of both of these materials (including leaving gaps where needed). The materials are isolated in the roads or beads of material as extruded.

[0276] When the G-Code is loaded in the machine, the printer follows the steps of:

[0277] (1) begin reading the model-specific G-Code file;

[0278] (2) heat-up thermoplastics printing nozzle and optionally, the build plate;

[0279] (3) move to home position to locate the origin reference point;

[0280] (4) start print code:

[0281] (a) extrude the thermoplastic (if any). In this example, a thermoplastic polyurethane was used;

[0282] (b) move the silicone extruder with nozzle to center;

[0283] (c) extrude silicone (via signal from printer to pressure regulator);

[0284] (d) move up to the next layer;

[0285] (e) extrude silicone;

[0286] (f) move the extruder with nozzle for the thermoplastic (TPU) to center;

[0287] (g) extrude the thermoplastic (TPU);

[0288] (h) move up to the next layer; and

[0289] (i) repeat from (4)(a) until print is complete

[0290] (5) return to home position;

[0291] (6) cool down heated elements; and

[0292] (7) End G-Code

[0293] After printing, the multi-material print was subjected to a curing cycle at 185°C for two hours to fully cure the specific silicone used (noted above) and to attain the desired tubular structure.

[0294] Figs. 29 and 30 show, respectively a top plan view and a perspective view of a tubular item printed using the above-noted procedure having an internal shell of reinforcing TPU (red) and an exterior shell of silicone (white) according to the programmed shape in Fig. 25.

[0295] Example 5: Silicon Composite Structures with Continuous Carbon Reinforcement

[0296] Two types of thermoset silicon-containing polymers capable of curing to silicone were used in the Examples, a one-part thermoset silicon and a two-part thermoset silicon polymer.

[0297] The one part thermoset silicon-containing polymer was a Primetech™ AMS 3302H silicon polymer. In a 10 mL, high pressure Nordson™ Ultimus V dispensing syringe, 8 g of the Primetech AMS 3302H silicone were loaded and compressed by hand to expel most of the air pockets. The syringe was then placed into a high pressure Nordson HPx syringe booster including a syringe band heater. The syringe band heater was slowly heated to the desired temperature for extrusion of the silicone (80°C -110°C).

[0298] The two-part thermoset silicon-containing polymer included Dow® Xiameter™ RBL 2004 Part A and Part B components mixed in a 1:1 ratio. Metered mixing equipment was used which pumped, metered and mixed the two components without incorporation of air. If air bubbles were entrapped during mixing, the air was degassed under vacuum.

[0299] The thermoset silicon-containing polymers were printed using a dual printhead design assembly is shown in Figures 33-35 and 37. For silicone printing in a first nozzle according to the invention, a high-pressure piston (Nordson™ HPx High Pressure Dispensing Tool, available from Nordson EFD, Westlake, OH) was used with a pneumaticbased high precision controller (Ultimus V, also available from Nordson EFD, Westlake, OH) with a maximum pressure of 100 psi (7 bar).

[0300] For printing of the continuous fiber using a second nozzle according to the invention, a Markforged™ fiber nozzle was installed on an E3D V6-all metal hot end (available from E3D-Online, Oxfordshire, UK). A Markforged™ desktop fiber extruder was fitted with the attached E3D hot end for fiber supply. Both nozzles, having the cylinder syringe and the E3D hot end were installed in LulzBot TAZ Dual Extruder Tool Head vl (Aleph Objects, Inc., Loveland, CO) as the print head using a mounting arm as shown in Figures 31-35 herein. As the continuous fiber needed to be cut regularly during the dual printing process, an automated wire cutter was designed, as shown in Figs. 33-35, 37D and 45. The fiber printhead and cutter were installed in a LulzBot TAZ 5 printer for dualextrusion printing.

[0301] The silicone printing temperature needed to be maintained at approximately 85- 90°C for good flow viscosity which was accomplished by attaching a 110 V 380 W heating element band heater (110 V 380 W, 35 x 35 mm, Nxtop™ of Shenzhen, China) having a connection to a PID controller and a thermocouple (ITC-106VH, Inkbird™ of Shenzhen, China) on the cylinder syringe of the dispenser. The diameters of the two types of continuous fibers used in this Example (carbon fiber and Kevlar® fiber) were 0.4 mm, which is considerably smaller than the 1.75 mm diameter of traditional FDM-type filaments. [0302] A PTFE tube as shown in Fig. 37 was inserted and connected to the second fiber nozzle to prevent any buckling and jamming of the fiber filament entering the hot end supply tube. [0303] A Nema 17 stepper motor and an A4988 stepper motor driver module as shown in Fig. 45 were applied to control the cutting mechanism rotation and cutting motions of the cutting device used. To cut the fiber at the top of the current printed layer, the printhead was set to lift up before the cutter rotated down to perform the cutting motion according to the steps in Fig. 46. During the lifting motion, the fiber extruder was set to continue extruding to prevent the extruder from gripping and dragging the deposited carbon fiber and unintentionally separating the fiber from the current printed layer. Therefore, the fiber extrusion was coordinated with the lifting and cutting motion of the printer in the design of the print process.

[0304] To promote good adhesion between the layer of printed silicone and layer of the long reinforcing fiber cut and printed from the extruded continuous reinforcing fiber, the fiber extrusion nozzle was found to operate best by being calibrated to align with the silicone syringe tip. When the fiber nozzle was positioned too low, some damage was experienced to the previously printed silicone layer. When the fiber nozzle was positioned too high, the reinforcing fiber did not adhere as well to the silicone layer. Based on the materials used in this process, and due to the small diameters of continuous fibers (0.4 mm) used in this Example, the layer height was set to 0 mm for good adhesion of the reinforcing fiber with silicone layer. For each printing road, the fiber needed to be pre-extruded a short length. Then the reinforcing fiber printhead moved to the fiber printing start position and stopped there for 10 s, so the print head could pre-extrude a length of reinforcing fiber and ensure that the reinforcing fiber fully touched the silicone layer surface. After such contact, the reinforcing fiber printhead continued to move forward to finish the deposition of the continuous fiber.

[0305] The printing parameters are listed in Table 3. The silicone section of specimens in this study was 3D printed with an 18-gauge, 1.041 mm precision dispensing nozzle (Fisnar™ Micron-S) with a 1 mm/s printing speed and an extrusion pressure of 63 psi. The silicone layer height and supply pressure used may be adjusted in further printing systems for different nozzle sizes. TABLE 3

[0306] Fig. 38A provides a photo of dog bone samples prepared as described below. Carbon fiber reinforced silicone composites were investigated for evaluating fiber reinforcement and anisotropy. Four types of dogbone-shaped tensile specimens prepared according to the standards in ASTM D412 by printing using the apparatus noted above. In Fig. 38 A, the samples are shown printed using (a) a perpendicular silicone orientation print direction (transverse direction), but without continuous long reinforcing fiber; (b) a perpendicular orientation as in (a) but including printing of continuous fiber in the form of long reinforcing fibers laid into a layer within the printed silicone; (c) a parallel orientation printing of silicone (in the longitudinal direction) without use of continuous reinforcing fiber; and (d) a parallel orientation silicone printing as in (c) but including use of continuous fiber to provide long reinforcing fibers in a layer within the printing.

[0307] In Fig. 38 A, the specimens had a “sandwich” structure when fiber was used with four fibers being printed between two layers of silicone. Tensile tests were performed at ambient temperature of about 20 °C on MTS Criterion® Electromechanical Test Systems equipped with 50kN load cell with 12 mm/min tension speed. The fiber reinforcement effect was evaluated by comparing the specimens either print direction, with and without use of continuous long fiber. The anisotropy effect was evaluated by perpendicular and parallel orientations. [0308] The dogbone-shaped tensile specimens of Fig. 38A were printed by the dualextrusion printer with the printing procedure described herein. The silicone section of specimens was printed by an 18-gauge, 1.041 mm precision dispensing nozzle (Fisnar Micron-S, Fisnar Inc., Wayne, NJ) with 1 mm/s printing speed, 85 °C printing temperature, 1 mm layer height, and an extrusion pressure of 63 psi. The carbon fiber section of specimens was printed by Markforged™ fiber nozzle with 0.5 mm/s printing speed, 270 °C printing temperature, and 0 mm layer height.

[0309] Figs. 39 and 40 show the strain-stress curves obtained from tension tests. Under stress, the silicone section of the specimens still fully gripped and stretched even under stretched tension and the slipping of the fibers. Fig. 39 shows the tensile test results comparing the parallel printed specimens with and without continuous fiber. With the reinforcement of fiber, the maximum tensile strength of the specimens before slipping is 14.49 MPa, which is around three times the tensile strength of the parallel specimens without fiber (4.40 MPa). The tensile test results of perpendicular printed specimens with and without continuous fiber are shown in Figure 40. The maximum tensile strength of fiber-reinforced perpendicular specimens is 17.25 MPa, but the specimens without fiber can only reach 2.83 MPa.

[0310] A comparison of the data from the different print directions demonstrated that without fiber reinforcement, specimens printed in a parallel (longitudinal) direction reached a higher tensile strength and a higher ultimate strain than specimen printed in a perpendicular (transverse) direction. Anisotropy is mainly attributed to voids in between adjacent printing lines and layers. Certain void volume is inevitably generated during the filament deposition and stacking up process of additive manufacturing printing. Thus, one can conclude that different printing directions likely is the result of different void volume fractions, which caused certain mechanical anisotropy.

[0311] Although the anisotropy exists in specimens without fiber reinforcement, the perpendicular specimens with fiber reinforcement were able to provide up to four times the tensile strength as the parallel specimens without fiber. Therefore, although silicone specimens without fiber demonstrate anisotropy in three-dimensional additive manufactured printed parts, fiber reinforcement may thus be employed to mitigate this issue. The anisotropic effect can be controlled and minimized by adjusting the volume ratio and orientation of continuous fibers in printed composites. In addition, continuous fibers with different mechanical and adhesion properties can be selected to achieve various anisotropy ratios and desired properties for resulting composites. [0312] Figure 38 shows additional tensile specimens printed in silicone with long reinforcing fiber. The silicone extrusion was oriented in both a parallel and a perpendicular direction with respect to the printing direction of the reinforcing fiber. Specimens using both Kevlar™ fiber and carbon fiber are shown. In this Example, the direction of fiber orientation is in a longitudinal direction of the tensile specimen. However, as noted elsewhere herein reinforcing fibers can be printed so as to be oriented in any direction in a reinforcing layer with respect to the direction of the layer of the extruded silicone and the longitudinal or transverse orientation of the printed specimen.

[0313] Fig. 38 shows (a) longitudinally extending Kevlar® fibers extending in the longitudinal direction of the printed slab specimens. The thermoset silicone-containing polymer is printed also in a parallel orientation with respect to the reinforcing fiber layer which is also in the longitudinal direction of the specimen. In Fig. 38 in specimen (b), the Kevlar® fiber layer is again printed in the longitudinal direction by the printed silicone layer in this example are printed in an orientation perpendicular to the reinforcing fiber and the printing extends in the transverse direction along the specimen. Fig. 38 in parts (c) and (d) are in the same orientations as Fig. 38 parts (a) and (b) respectively, but instead of Kevlar® reinforcing fiber, carbon reinforcing fiber was used in (c) and (d). Each of the specimens were printed to be 18 mm in width measured in the transverse direction, 88.9 mm in length measured in the longitudinal direction, where the transverse and longitudinal dimensions are in an x-y plane, and 1.3 mm in thickness measured in a z-direction perpendicular to the plane of the length and width across the specimen. The fiber tows were printed so as to have a 2 mm spacing transversely between each fiber tow. The layer height for each silicone-printed layer was 0.686 mm, and one layer of fiber.

[0314] Figure 38 shows photographic images of the printed silicone specimens in slab form reinforced with Kevlar fiber tows or carbon fiber tows as noted above, wherein the silicone was printed for each type of fiber in the longitudinal (parallel) and transverse (perpendicular) directions of printing and with respect to the fibers which were laid in the longitudinal direction during the additive printing of the specimens.

[0315] The tensile data shown below was taken in the direction of the fibers. Figures 43 and 44 show stress-strain curves from the tensile specimens in Figures 38 (specimens (a), (b), (c) and (d)). As can be observed in Figs. 43-44, the samples showed high stress (between 10 and 18 MPa) at low extensions between 20 % and 150 % elongation. At this point, the samples yielded, and the fibers began to slip in the silicone matrix. The high extension portion of the curves, above 150 % to 200 % elongation, illustrates the effect of the stretching of the silicone matrix after the fibers experienced slippage. Both Kevlar and carbon fiber tows showed similar behavior and slippage. Fiber tow slippage can be reduced or minimized in a number of ways, including use of sizing agents on the fibers, coextrusion onto the fibers as described above in this disclosure, designed interfacial chemistry, functionalization of the silicone or any sizing or coating on the fibers, interfacial or matrix crosslinking, use of adhesives, or other strategies to help to bind the silicone matrix more tightly to the fiber tows.

[0316] Fig. 41 shows an example of a fiber-reinforced silicone ring printed three- dimensionally using the apparatus described in this example and the conditions as noted above. Figs. 42A-42D illustrate a three-dimensional model for a curved tube with long fiber reinforcement (Fig. 42A) along with views of the top (Fig. 42B) and left and right ends (Figs. 42C and 42D, respectively) of a three-dimensional printed object printed using the apparatus described in this Example. Other shapes and configurations may be similarly printed.

[0317] Example 6: Identification of Key Factors for Preferred Three Dimensional Additive Manufacturing Printing of Articles Using Silicone

[0318] As part of this Example, the applicant evaluated the impact of viscosity on printing by employing a high viscosity at a zero shear rate and using low viscosity at high shear rates to identify preferred parameters for preferred silicon-containing polymers, i.e., printing silicone while achieving preferred printed articles having desired properties using silicone. Sample A (a Dow Xiameter™ RBL 2004-50 silicone) was sheared at rates in the range of 10/s to 950/sec and the corresponding apparent viscosity data was measured. Similar experiments were carried out for several silicones, including Sample B (Elkem 20501-50) and Sample C (a mixed blend of 50 parts by weight of Xiameter™ RBL 2004-50 part A silicone and 50 parts by weight Xiameter™ 2004-50 Part B silicone, per 100 parts by weight of total elastomers, and including 3 parts per 100 parts by weight of the total elastomers of Evonik Aerosil® R972 to modify the Bingham plastic behavior of the Xiameter silicones). This data is shown in Fig. 47 as a graphical representation of the shear rate against the apparent viscosity of Samples A-C, which data was extrapolated to obtain the apparent viscosity of Samples A-C at zero shear rate.

[0319] To identify the range of preferred applied pressure for achieving a desired additive manufacturing printing latitude, further evaluation was conducted. It is preferred to have a broad additive manufacturing printing speed range for printing articles from various silicones. For example, a one-part peroxide curable silicone, Primetech™ AMS 3302H, exhibits excellent shape-holding at a very high zero shear viscosity of greater than about 100,000 poise. However, that same silicone exhibits very poor shear thinning and as a result, printing speed for that material is less than 1 mm/s even when applying a high pressure of about 120 psi. By comparison, a two-part, platinum-curable silicone in Sample D (Dow SE-1700), has a printing speed that can be increased from a low printing speed of about 2 mm/s to a high printing speed of about 70 mm/s quickly by increasing pressure from about 2 psi to about 15 psi. The other two-part silicones tested, such as Samples A-C noted above also have a broad printing speed range of about 2 mm/sec to 70 mm/sec by increasing the pressure in the range of 20 to 100 psi as shown in Fig. 48.

[0320] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Claims

CLAIMS We claim:

1. A method for forming composite articles comprising thermoset silicon-containing polymers, comprising:

(a) providing a first composition comprising a first thermoset silicon- containing polymer;

(b) providing a thermoplastic composition;

(c) printing, using an additive manufacturing device:

(i) a first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer using an additive manufacturing device; and

(ii) an at least partial reinforcing layer comprising the thermoplastic composition, wherein the first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial reinforcing layer are printed either to be within the same layer or in successive layers.

2. The method according to claim 1, wherein the first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer is printed on a substrate.

3. The method according to claim 1, wherein the first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial reinforcing layer are complete individual layers printed in at least two successive layers.

4. The method according to claim 3, wherein the first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer is printed on a substrate.

5. The method according to claim 1, wherein the first at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial reinforcing layer are printed so as to be within a single layer.

6. The method according to claim 1, wherein the first thermoset silicon-containing polymer comprises at least one polymer selected from the group of a polysiloxane; a polyalkylsiloxane; a polydialkylsiloxane; and combinations, or co-polymers thereof.

7. The method according to claim 1, wherein the first thermoset silicon-containing polymer comprises at least one functional group selected from the group consisting of hydroxyl, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkenoxy, alkynoxy, aryloxy, arylalkyl, arylalkoxy, arylalkenoxy, vinyl, carboxyl, carbonyl, halogen, heterocyclic, and fluorinated and perfluorinated groups thereof.

8. The method according to claim 1, wherein the first composition comprising the first thermoset silicon-containing polymer comprises one or components selected from the group consisting of a curative, a cure catalyst, an organic peroxide, a hydrolytic crosslinker, a siloxane additive, an ultra-high-molecular-weight siloxane additive, clarifiers, UV absorbers, optical brighteners, pigments, colorants, stabilizers, flame-retardants, quartz, pyrogenic silica, carbon black, fluorinated or perfluorinated polymer additives, and nanosilica dioxide particles.

9. The method according to claim 1, wherein the thermoplastic composition comprises at least one thermoplastic selected from the group consisting of polyolefins, polyoxymethylene, polyamides, polyesters, polyimides, polyarylene ethers, polyarylene ether ketones, polyarylene ether sulfones, polyphenylene oxide blended with polystyrene, polyacrylonitrile-butadiene-styrene, polystyrene-acrylonitrile, polyacrylonitrile, polystyrene, polyethylene terephthalate, polyethylene terephthalate glycol, thermoplastic elastomers and thermoplastic polyurethanes, and copolymers, blends, alloys, and derivatives thereof.

10. The method according to claim 1, wherein the reinforcing layer may comprise fibers.

11. The method according to claim 1 , further comprising printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon- containing polymer on the first at least partial layer thereof prior to printing the at least partial reinforcing layer.

12. The method according to claim 1, further comprising printing one or more additional at least partial reinforcing layers comprising the thermoplastic composition on the at least partial reinforcing layer.

13. The method according to claim 1, further comprising successively, and in an alternating manner, printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer and one or more additional at least partial reinforcing layers comprising the thermoplastic composition on the at least one reinforcing layer.

14. The method according to claim 1, further comprising compression molding the article formed by the method into a modified article.

15. A three-dimensional article formed from the method of claim 1, having a composite structure comprising at least one at least partial layer of the first composition comprising the thermoset silicon-containing polymer and at least one partial layer of the reinforcing composition comprising the thermoplastic.

16. The method according to claim 1, further comprising

(e) providing a second composition comprising a second thermoset silicon-containing polymer; and

(f) printing at least partial first layer of the second composition comprising the second thermoset silicon-containing polymer on the at least partial reinforcing layer using an additive manufacturing device.

17. The method according to claim 16, wherein the first at least partial layer of the second composition comprising the second thermoset silicon-containing polymer is a complete layer and the at least partial reinforcing layer is a complete layer.

18. The method according to claim 16, wherein the first at least partial layer of the second composition comprising the second thermoset silicon-containing polymer and the at least partial reinforcing layer are printed so as to be within a single layer.

19. The method according to claim 16, wherein the first thermoset silicon-containing polymer and/or the second thermoset silicon-containing polymer comprise at least one polymer selected from the group of a polysiloxane; a polyalkylsiloxane; a polydialkylsiloxane; and combinations, or co-polymers thereof.

20. The method according to claim 16, wherein the first thermoset silicon-containing polymer and/or the second thermoset silicon-containing polymer comprise at least one functional group selected from the group consisting of hydroxyl, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkenoxy, alkynoxy, aryloxy, arylalkyl, arylalkoxy, arylalkenoxy, vinyl, carboxyl, carbonyl, halogen, heterocyclic, and fluorinated and perfluorinated groups thereof.

21. The method according to claim 16, wherein the first composition comprising the first thermoset silicon-containing polymer and/or the second composition comprising the second thermoset silicon-containing polymer comprises one or components selected from the group consisting of a curative, a cure catalyst, an organic peroxide, a hydrolytic crosslinker, a siloxane additive, an ultra-high-molecular-weight siloxane additive, clarifiers, UV absorbers, optical brighteners, pigments, colorants, stabilizers, flame -retardants, quartz, pyrogenic silica, carbon black, fluorinated or perfluorinated polymer additives, and nanosilica dioxide particles.

22. The method according to claim 16, wherein the first thermoset silicon-containing polymer and the second thermoset silicon-containing polymer are the same.

23. The method according to claim 16, wherein the first composition comprising the first thermoset silicon-containing polymer and the second composition comprising the second thermoset silicon-containing polymer are the same.

24. The method according to claim 16, wherein the thermoplastic composition comprises at least one thermoplastic selected from the group consisting of polyolefins, polyoxymethylene, polyamides, polyesters, polyimides, polyarylene ethers, polyarylene ether ketones, polyarylene ether sulfones, polyphenylene oxide blended with polystyrene, polyacrylonitrile-butadiene-styrene, polystyrene-acrylonitrile, polyacrylonitrile, polystyrene, polyethylene terephthalate, polyethylene terephthalate glycol, thermoplastic elastomers and thermoplastic polyurethanes, and copolymers, blends, alloys, and derivatives thereof.

25. The method according to claim 16, further comprising printing one or more successive at least partial layers of the first composition comprising the first thermoset silicon-containing polymer on the first at least partial layer thereof prior to printing the at least partial reinforcing layer.

26. The method according to claim 16, further comprising printing one or more successive at least partial reinforcing layers comprising the thermoplastic composition prior to printing the first at least partial layer of the second composition comprising the second thermoset silicon-containing polymer.

27. The method according to claim 16, further comprising printing one or more successive at least partial layers of the second composition comprising the second thermoset silicon-containing polymer on the first at least partial layer of the second composition comprising the second thermoset silicon-containing polymer.

28. The method according to claim 16, further comprising successively, and in an alternating manner, printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer, one or more additional at least partial reinforcing layers comprising the thermoplastic composition, and one or more additional at least partial layers of the second composition comprising the second thermoset silicon-containing polymer according to a designed pattern on the first at least partial layer of the second composition comprising the second silicon containing polymer.

29. The method according to claim 28, wherein each of the at least partial layers of the first composition comprising the first thermoset silicon-containing polymer, each of the at least partial reinforcing layers comprising the thermoplastic composition, and each of the at least partial layers of the second composition comprising the second thermoset silicon- containing polymer is printed as a complete layer.

30. The method according to claim 16, further comprising compression molding the article formed by the method into a modified article.

31. The method according to claim 16, further comprising repeating steps (c), (d) and (f) to form an article based on a computer design model.

32. The method according to claim 16, wherein the article comprises a configuration that is a tubular or a cylindrical solid article.

33. A three-dimensional article formed from the method of claim 16, having a composite structure comprising at least one at least partial layer of the first composition comprising the thermoset silicon-containing polymer, at least one at least partial layer of the reinforcing composition comprising the thermoplastic and at least one at least partial layer of the second composition comprising a thermoset silicon-containing polymer.

34. The three-dimensional article according to claim 33, wherein the article is an O-ring, a seal, a gasket, a medical device, a medical implant, or a component part thereof.

35. The three-dimensional article according to claim 33, wherein the three-dimensional article is further subjected to compression molding to form a modified article.

36. An apparatus for preparing a composite article comprising thermoset silicon- containing polymers, comprising: an additive manufacturing printer having a printer drive mechanism, a first printing nozzle for forming a first at least partial layer of a first composition; and a second printing nozzle for forming a second at least partial layer of a second composition, wherein the additive manufacturing printer is capable of providing two or more at least partial layers of each of the first and the second composition to form a three- dimensional composite article of the first and the second compositions according to a computer design model, and wherein at least one of the first printing nozzle and the second printing nozzle is a pressurized printing nozzle comprising a heating mechanism in operable contact therewith.

37. The apparatus according to claim 36, wherein the first composition and the second composition are the same.

38. The apparatus according to claim 36, wherein the first composition comprises a first thermoset silicon-containing polymer and the second composition comprises either a second thermoset silicon-containing polymer or a thermoplastic polymer.

39. The apparatus according to claim 38, wherein when the first composition comprises the first thermoset silicon-containing polymer and the second composition comprises the second thermoset silicon-containing polymer, each of the first nozzle and the second nozzle is a pressurized nozzle.

40. The apparatus according to claim 38, wherein the first thermoset silicon-containing polymer and the second thermoset silicon-containing polymer are the same.

41. The apparatus according to claim 36, wherein the apparatus comprises a third printing nozzle for forming a third layer of a third composition.

42. The apparatus according to claim 41, wherein the third composition is the same as the first and/or the second compositions.

43. The apparatus according to claim 36, wherein at least one of the printing nozzles is operably programmed in the computer design model to print an at least partial layer in a design pattern.

44. The apparatus according to claim 43, wherein the at least partial layer in the design pattern as a thermoplastic layer.

45. The apparatus according to claim 36, wherein the first and/or the second composition is in the form of a filament.

46. The apparatus according to claim 36, wherein the first nozzle and the second nozzle are part of a nozzle assembly that further includes a mounting arm to stably hold the first nozzle and the second nozzle in position for tandem operation.

47. The apparatus according to claim 46, wherein the mounting arm has a transversely extending support portion for supporting the second nozzle and a seat support portion having an opening therethrough to support the first nozzle.

48. The apparatus according to claim 46, wherein the nozzle assembly further comprises a nozzle assembly printer drive mechanism.

49. The apparatus according to claim 36, wherein the first nozzle is a high pressure piston extruder.

50. The apparatus according to claim 49, wherein the first nozzle is in communication with a pressurized source.

51. The apparatus according to claim 49, wherein the first nozzle has a nozzle end portion and a heating band is adapted to be positioned around the nozzle end portion for heating a composition having a thermoset silicon-containing polymer as it is printed by the nozzle.

52. The apparatus according to claim 36, wherein the second nozzle is a thermoplastic nozzle extruder.

53. The apparatus according to claim 36, wherein the second nozzle is a fiber nozzle extruder.

54. A method for forming composite articles comprising thermoset silicon-containing polymers and long reinforcing fiber, comprising: (d) providing a first composition comprising a first thermoset silicon- containing polymer;

(e) providing a continuous long reinforcing fiber;

(f) printing at least a partial layer of the first composition comprising the first thermoset silicon-containing polymer using a first nozzle of an additive manufacturing device; and

(g) printing at least a partial layer of long reinforcing fibers using a second nozzle of the additive manufacturing device, wherein the at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial layer of long reinforcing fibers are printed either to be within the same layer or in successive layers.

55. The method according to claim 54, wherein the at least partial layer of the first composition comprising the first thermoset silicon-containing polymer is printed on a substrate.

56. The method according to claim 54, wherein the at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial layer of long reinforcing fibers are complete individual layers printed in at least two successive layers.

57. The method according to claim 56, wherein the at least partial layer of the first composition comprising the first thermoset silicon-containing polymer is printed on a substrate.

58. The method according to claim 54, wherein the at least partial layer of the first composition comprising the first thermoset silicon-containing polymer and the at least partial layer of long reinforcing fibers are printed so as to be within a single layer.

59. The method according to claim 54, wherein the first thermoset silicon-containing polymer comprises at least one polymer selected from the group of a polysiloxane; a polyalkylsiloxane; a polydialkylsiloxane; and combinations, or co-polymers thereof.

60. The method according to claim 54, wherein the first thermoset silicon-containing polymer comprises at least one functional group selected from the group consisting of hydroxyl, alkyl, alkenyl, alkynyl, aryl, alkoxy, alkenoxy, alkynoxy, aryloxy, arylalkyl, arylalkoxy, arylalkenoxy, vinyl, carboxyl, carbonyl, halogen, heterocyclic, and fluorinated and perfluorinated groups thereof.

61. The method according to claim 54, wherein the first composition comprising the first thermoset silicon-containing polymer comprises one or components selected from the group consisting of a curative, a cure catalyst, an organic peroxide, a hydrolytic crosslinker, a siloxane additive, an ultra-high-molecular-weight siloxane additive, clarifiers, UV absorbers, optical brighteners, pigments, colorants, stabilizers, flame-retardants, quartz, pyrogenic silica, carbon black, fluorinated or perfluorinated polymer additives, and nanosilica dioxide particles.

62. The method according to claim 54, wherein the long reinforcing fibers are selected from the group consisting of carbon fiber, glass fiber, boron fiber, alumina fiber, silicon carbide fiber, quartz fiber, aramid fiber, polybenzoxazole fiber, ultra-high molecular weight polyethylene fiber, polypropylene, polyethylene terephthalate, polyethylene, polyimide, polyarylesters, polyetherimide, polyvinyl alcohol, rayon, polyacrylonitrile fibers, and natural and synthetic fiber blends.

63. The method according to claim 62, wherein the long reinforcing fiber is a natural fiber selected from the group consisting of keratin, flax, viscose, sisal, hemp and jute.

64. The method according to claim 62, wherein the long reinforcing fibers are selected from the group consisting of carbon fibers, aramid fibers, and glass fibers.

65. The method according to claim 54, wherein the long reinforcing fiber is provided as one of a single fiber, a fiber tow, a fiber bundle, a braid, a blend of fibers, or as hybrid fiber bundles.

66. The method according to claim 54, wherein the method further comprises cutting the long continuous fiber as the fiber leaves the second nozzle using a fiber cutting device.

67. The method according to claim 54, wherein the printing the first thermoset silicon- containing polymer using the first nozzle further comprises heating the first nozzle of the additive manufacturing device.

68. The method according to claim 54, wherein printing the long reinforcing fiber using the second nozzle further comprises heating the second nozzle.

69. The method according to claim 54, further comprising co-extruding a composition comprising an extrudable polymeric material over the long reinforcing fiber.

70. The method according to claim 69, wherein the extrudable polymeric material is a thermoplastic composition or a second composition comprising a second thermoset silicon- containing polymer.

71. The method according to claim 70, wherein the first thermoset silicon-containing polymer is different from the second thermoset silicon-containing polymer.

72. The method according to claim 70, wherein the extrudable polymeric material is a thermoplastic composition that comprises at least one thermoplastic selected from the group consisting of polyolefins, polyoxymethylene, polyamides, polyesters, polyimides, polyarylene ethers, polyarylene ether ketones, polyarylene ether sulfones, polyphenylene oxide blended with polystyrene, polyacrylonitrile-butadiene-styrene, polystyreneacrylonitrile, polyacrylonitrile, polystyrene, polyethylene terephthalate, polyethylene terephthalate glycol, thermoplastic elastomers and thermoplastic polyurethanes, and copolymers, blends, alloys, and derivatives thereof.

73. The method according to claim 69, wherein the composition comprising the extrudable polymeric material comprises one or more reinforcing fibers.

74. The method according to claim 54, wherein the first composition comprising the first thermoset silicon-containing polymer comprises one or more reinforcing fibers.

75. The method according to claim 54, further comprising printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer on the at least partial layer thereof prior to or after printing the at least partial layer of long reinforcing fibers.

76. The method according to claim 54, further comprising printing one or more additional at least partial layers of the long reinforcing fibers.

77. The method according to claim 54, further comprising successively, and in an alternating manner, printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer and one or more additional at least partial layers of the long reinforcing fibers comprising the thermoplastic composition on the at least one reinforcing layer.

78. The method according to claim 54, further comprising printing the at least partial layer of the first composition comprising the first thermoset silicon-containing polymer in a generally transverse direction and printing the at least partial layer of the long reinforcing fibers in a second generally longitudinal direction.

79. The method according to claim 54, further comprising compression molding the composite article formed by the method into a modified composite article.

80. A three-dimensional composite article formed from the method of claim 54, having a composite structure comprising at least one of the at least partial layer of the first composition comprising the thermoset silicon-containing polymer and at least one of the at least one partial layer of the long reinforcing fibers.

81. The three-dimensional article according to claim 80, wherein the article is an O-ring, a seal, a gasket, a medical device, a medical implant, or a component part thereof.

82. The method according to claim 54, further comprising

(e) providing a second composition comprising a second thermoset silicon-containing polymer; and (f) printing at least a partial first layer of the second composition comprising the second thermoset silicon-containing polymer on the at least partial layer of the long reinforcing fibers using the additive manufacturing device.

83. The method according to claim 82, wherein the first at least partial layer of the second composition comprising the second thermoset silicon-containing polymer is a complete layer.

84. The method according to claim 82, wherein the first thermoset silicon-containing polymer and the second thermoset silicon-containing polymer are the same.

85. The method according to claim 82, further comprising repeating steps (c), (d) and (f) to form an article based on a computer design model.

86. The method according to claim 54, further comprising according to a designed pattern, printing one or more additional at least partial layers of the first composition comprising the first thermoset silicon-containing polymer and one or more additional at least partial layers of the long reinforcing fibers.

87. The method according to claim 86, further comprising printing one or more additional at least partial layers of a second composition comprising a second thermoset silicon-containing polymer.

88. The method according to claim 54, further comprising repeating steps (c) and (d) to form an article based on a computer design model.

89. An apparatus for preparing a composite article comprising thermoset silicon- containing polymers and long continuous fibers, comprising: an additive manufacturing printer having a printer drive mechanism, a first nozzle for forming an at least partial layer of a first composition; and a second nozzle for forming an at least partial layer of a long reinforcing fiber, a fiber cutting device positioned for cutting the long reinforcing fiber leaving the second nozzle, wherein the additive manufacturing printer is capable of providing one or more at least partial layer of each of the first composition and one or more of the at least partial layer of the long reinforcing fiber to form a three-dimensional composite article of the first composition and the long reinforcing fiber according to a computer design model, and wherein at least one of the first nozzle and the second nozzle is a pressurized printing nozzle comprising a heating mechanism in operable contact therewith.

90. The apparatus according to claim 89, wherein the first composition comprises a first thermoset silicon-containing polymer.

70

91. The apparatus according to claim 89, further comprising a third printing nozzle for forming a third layer of a second composition.

92. The apparatus according to claim 91, wherein the second composition comprises an extrudable polymeric material.

93. The apparatus according to claim 89, wherein the first nozzle and the second nozzle are heated.

94. The apparatus according to claim 89, wherein the second nozzle is capable of coextruding an extrudable polymeric material over the long reinforcing fiber.

95. The apparatus according to claim 89, wherein at least one of the first and the second nozzles is operably programmed in the computer design model to print an at least partial layer in a design pattern.

96. The apparatus according to claim 95, wherein the first and the second nozzles are both operably programmed in the computer design model to print at least partial layers of the first composition and of the long reinforcing fiber in the design pattern.

97. The apparatus according to claim 89, wherein the first composition is provided in the form of a filament.

98. The apparatus according to claim 89, wherein the first nozzle and the second nozzle are part of a nozzle assembly that further includes a mounting arm to stably hold the first nozzle and the second nozzle in position for tandem operation.

99. The apparatus according to claim 98, wherein the mounting arm has a support base for supporting the first and the second nozzle and is operably and releasably connectable to the fiber cutting device, wherein the support base has respective openings therethrough to support the first nozzle and the second nozzle.

100. The apparatus according to claim 89, wherein the first nozzle is a high pressure piston extruder.

101. The apparatus according to claim 100, wherein the first nozzle is in communication with a pressurized source.

102. The apparatus according to claim 101, wherein the first nozzle has a nozzle end portion and a heating band is adapted to be positioned around the nozzle end portion for heating a composition having a thermoset silicon-containing polymer as it is printed by the nozzle.

103. The apparatus according to claim 89, wherein the second nozzle is a long reinforcing fiber extruder.

104. The apparatus according to claim 103, wherein the second nozzle is configured to receive an extrudable polymeric material to co-extrude over the long reinforcing fiber.

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105. The apparatus according to claim 89, wherein the fiber cutting device is operable to continuously cut long reinforcing fiber at a controlled interval length while printing the at least partial layer of long reinforcing fiber.

106. The apparatus according to claim 103, wherein the second nozzle has a nozzle end portion and a heating band is adapted to be positioned around the nozzle end portion for heating the long reinforcing fiber.

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