TWI496820B - Engineered cross-linked thermoplastic particles for interlaminar toughening - Google Patents

Description

Engineered crosslinked thermoplastic particles for interlaminar toughening

The present invention relates to an engineered particle that can be used in an interlaminar toughened composite article. More particularly, the present invention relates to an engineered crosslinked particle having a thermoplastic polymer backbone wherein the particles are insoluble in the resin system and maintain discrete particles upon curing.

The functionalized acrylonitrile-butadiene rubber has been used for toughening thermosetting adhesives and composites many years ago; U.S. Patent Nos. 3,926,904 and 4,500,660. These toughening agents have been found to be soluble in the uncured thermosetting resin, however, they are subsequently phase separated during curing to create a rubberized area throughout the matrix.

It is also claimed, as generally described, that the rubber particles can be crosslinked in situ by RIPS (resin induced phase separation). These rubbers have proven to be useful for toughening, however, they generally reduce the thermo-wet mechanical properties of the composite. This decrease in heat and humidity performance limits the application of rubber in aerospace equipment.

Functionalized and unfunctionalized thermoset plastics, such as polyether oximes, have also been found to increase the toughness of the composite without significantly reducing the heat and moisture properties; U.S. Patent No. 4,656,207. These thermoplastics behave similarly to the rubbers described above; they dissolve into the uncured resin and separate from the resin phase during curing.

No. 4,539,253 and 4,604,319 to Hirschbuehler et al. disclose that a greater toughness increase can be obtained by concentrating the toughening agent between the layers of the composite. Thermoplastic particles can be embedded in the resin by this principle, which remain substantially insoluble during the manufacture of the prepreg film, and then subsequently dissolved in the resin and phase separated during curing, U.S. Patent Nos. 4,954,195, 4957,801. , 5,276,106 and 5,434,224. These particles are large enough to pass through the fibers to the intermediate layer region between the layers. Thus, when the particles are dissolved, a higher concentration of thermoplastic material can be produced in the intermediate layer than would be produced by dissolving the thermoplastic material prior to the manufacture of the prepreg.

Another method for increasing the toughness of the intermediate layer region is to embed insoluble particles. A number of patents describing the embedding of pre-formed rubber particles have been published by Gawin and others; U.S. Patent Nos. 4,783,506, 4,977,215, 4,977,218, 4,999,238, 5,089,560 and 6,013,730. These particles are also large enough to filter them through the fiber bundle into the intermediate layer region. Further, although they are insoluble, they may be expanded in the resin. Newer metals, U.S. Patent Nos. 5,266,610 and 6,063,839 use core-shell rubber particles for the same purpose. Similarly, polyfluorene-based particles have also been developed for the purpose of toughening, U.S. Patent No. 5,082,891.

The insoluble thermoplastic particles are used as an intermediate layer toughening agent to avoid loss of heat and moisture properties as described in U.S. Patent Nos. 4,957,801, 5,087,657, 5,242,748, 5,434,226, 5,605,745, and 6,117,551. However, such insoluble particles are generally made of a polymer which does not dissolve or swell in the resin composition, and is self-precipitating or grinding.

Several variations of polyamine/nylon particles have been disclosed to enhance the toughening ability of the particles. One variation, U.S. Patent No. 5,028,478, tests the incorporation of a crosslinked epoxy amine network into the particles to increase the solvent resistance of the particles. Other variations, U.S. Patent Nos. 5,169,710 and 5,268,223, test the manufacture of porous particles which promote the interaction of the particles with the resin.

Many such as nylon or Ultem The high Tg thermoplastic has sufficient toughness to be equal to no wear under non-cryogenic conditions. To take advantage of these polymers and polymers similar to those of the type such as PPO/PS alloys, a method is needed to make particles having useful particle sizes.

Therefore, there is a need to further improve thermoplastic particles for the toughening of composites and methods for making such particles. Even insoluble after curing, thermoplastic granules providing improved toughness, failure tolerance, heat and moisture resistance, microcrack resistance and reduced solvent sensitivity are useful materials of the art and can be rapidly transported especially in large commercial applications. And/or military aerospace industry is recognized.

The present invention provides thermoplastic particles having the primary function as a toughening agent for the intermediate layer of the composite. The particles remain insoluble in the resin system upon curing, thereby increasing the toughness and failure tolerance of the composite article. Composites made from such particles exhibit a damage tolerance that is 25% or greater greater than a composite containing the thermoplastic polymer in dissolved form. Other properties enhanced by the use of the thermoplastic particles of the present invention in composite articles include reduced solvent sensitivity, improved heat and moisture characteristics, improved processing characteristics with respect to prepregs, and resistance to microcracking.

Thus, in one aspect of the invention described in detail herein, an engineered particle is provided which is comprised of a plurality of thermoplastic polymer backbones having one or more polymers and one or more reactive groups. a polymer chain; and a crosslinker composition such that the crosslinker chemically reacts with the reactive groups of the polymer, thereby allowing the polymer chains to directly crosslink with each other via the reactive groups.

In another aspect, the invention provides an engineered particle comprising a plurality of polymer chains having a thermoplastic polymer backbone comprising one or more polymers, and having one or more reactive groups One or more compounds, and one chemically reactive with the reactive groups and polymerizable by the reactive groups, thereby forming an interpenetrating polymer between the polymer chain and the crosslinked network The network consists of a cross-linking network composed of cross-linking agents.

In yet another aspect, the present invention provides a resin system comprising a thermosetting resin and a plurality of engineered particles in accordance with the present invention. The invention further provides a prepreg comprising the engineered particles and/or the resin system according to the invention as described in detail herein, and a composite article formed from the prepreg.

The invention also includes a method of making the engineered particles described herein by dissolving a thermoplastic polymer and a crosslinking agent or a crosslinking network, if present, in a solvent, by polymerizing the polymer in the presence of one or more stabilizers. The solvent mixture is mixed with the immiscible solution to form an emulsion, the solvent is stripped of the emulsion to form solid particles, and the solid particles are solidified, thereby crosslinking the polymer chains in the particles or forming an interpenetrating polymer network.

In another aspect, the present invention provides a method of making a composite article having increased toughness and failure tolerance by adding a plurality of engineered particles in accordance with the present invention to a thermosetting resin system to form a plurality of preforms The dip film is laminated, the prepreg films are laminated to form a shaped article, and the article is cured to form a composite article having increased toughness and damage tolerance.

The above and other objects, features and advantages of the present invention will become apparent from the Detailed Description

As described above, the present invention provides novel polymer particles which can be used in the interlayer-enriched resin region of a thermosetting substrate to improve mechanical properties such as CAI, G _IC , G _IIC , OHC and the like. The particles of the present invention are partially or completely insoluble in the thermosetting resin matrix and remain as discrete particles even after curing processing. The present invention provides two methods to obtain polymer particles having partial or complete insolubility. One method involves directly crosslinking the chains with one or more reactive groups to "tying-up" the soluble polymer molecules. The second method involves bundling soluble polymer molecules by forming separate and independent cross-linking networks, thereby fabricating an interpenetrating network (IPN) or semi-IPN. Thus, the thermoplastic polymer particles described herein can be thermodynamically compatible with thermosetting resins such as epoxy resins and are chemically crosslinked to prevent them from being so soluble in the resin. The degree of cross-linking affects the diffusion of the uncured thermosetting resin into the particles. One advantage includes strong bonding between the particles and the resin matrix and good stress transfer due to the generation of particles having an intermediate phase between the particles and the surrounding resin matrix. Another advantage of crosslinked particles includes imparting improved solvent resistance and microcracking of the particles in the composite. These particles impart improved post-collision toughness compression (CAI), fracture toughness or delamination resistance ( _GIC , _GIIC ) of modes I and II without affecting fluid sensitivity characteristics. Another benefit of this technology is the ability to tailor particle characteristics to specific epoxy formulations. The granules, compositions comprising the granules and related methods and related advantages are described in more detail below.

Thus, in one aspect, the invention provides an engineered particle having a plurality of polymer chains comprising a thermoplastic polymer backbone comprising one or more thermoplastic polymers and one or more reactions a crosslinking group; and a crosslinking agent chemically reactive with the reactive group such that the crosslinking agent directly crosslinks the polymer chains with each other by a reactive group. Since this method is based on direct crosslinking of the chain, the reactive groups of the chain are not capped and the chains are not chemically inert (ie, each chain needs to have at least one type of reactive group). In a particular embodiment, the reactive group is at the end of the chain. In other cases, the reactive group can be located anywhere on the backbone of each chain.

In another aspect, the invention provides an engineered particle having a plurality of polymer chains comprising a thermoplastic polymer backbone, the thermoplastic polymer backbone comprising one or more thermoplastic polymers; A crosslinked network of one or more compounds polymerized from one or more reactive groups, wherein the polymer chains and the crosslinked network together form an interpenetrating (or semi-interpenetrating) network. Thus, since this method is based on a separate crosslinked network to wrap the polymer chain, the polymer chain can have reactive groups or be chemically inert. Thus, in some embodiments of the particles described herein, the thermoplastic polymer chains have reactive groups (located at the end or anywhere on the chain). In other embodiments of the particles of the present invention, the thermoplastic polymer chains do not have reactive groups. In other embodiments of the particles of the present invention, the plurality of polymer chains may mix some of the chains with reactive groups and some chains having no reactive groups.

The term "plural" as used herein has the same meaning as commonly understood by those skilled in the art and includes 2 or a numerical term that can vary. For example, "plurality of polymer chains" means two or more polymer chains.

The term "thermoplastic material" as used herein has a thermoplastic material as is known to those skilled in the art and includes a thermoplastic polymer backbone comprising the engineered crosslinked thermoplastic particles described herein. In some embodiments, the thermoplastic material can be polycarbonate, polyetherimide (PEI), polyamine, polyimine, polyfluorene, polyether oxime (PES), polyphenylene ether (PPO), Polyether ketone, polyphenyl sulfide (PPS), polyhydroxy ether, styrene-butadiene, polyacrylate, polyacetone alcohol, polybutylene terephthalate, polyamido-imine, polyether One or more of ether oxime (PEES), blends thereof, or the like, such as PES/PEES, PES homopolymers having various repeating unit ratios (such as PES 5003P from Sumitomo or obtained from Solvay polymers Radel PES) or PEES homopolymer. An example of a thermoplastic backbone is manufactured by Cytec Engineered Materials, Inc., such as HC99, also known as KM. 180 PES copolymer, a proprietary amine terminated by a PES-PEES thermoplastic. Therefore, the above thermoplastic material can be used as a single component for forming particles, or when more than one thermoplastic polymer is used, a hybrid structure or hybrid particles can be formed. The thermoplastic polymer backbone may also comprise any aromatic polymer, copolymer or oligomer containing decylamine, hydrazine, ketone, quinone imine, ester, ether, biphenyl, sulfide and carbonate linkages and any And so on. The thermoplastic backbone can also comprise any polymer, copolymer or oligomer comprising a rubber or elastomeric unit, such as a decane or a polybutadiene. The doped thermoplastic material also belongs to applicable materials, such as polyphenylene oxide-polystyrene alloy and toughened PPO (NORYL from SABIC-IP) ), hydrazine-modified polyether oximine (SILTEM from SABIC-IP) And toughened polyamidimide (EXTEM from SABIC-IP) ). Thus, in a particular embodiment, the engineered particles of the present invention may comprise a thermoplastic polymer chain as a single component. In other embodiments, the engineered particles can be present as a blend of thermoplastic polymers. In other embodiments, the particles described herein can be made from a hybrid structure in which two or more thermoplastic polymers are used. The amount of thermoplastic material of the engineered particles of the present invention may range from 1 to 99% by weight of the total particles.

In addition to the chemical structure of the polymer backbone, polymer molecular weight is another way of controlling the overall crosslink density of the particles. In the case where cross-linking occurs at the end of the polymer chain, a shorter molecule can attain a higher maximum crosslink density. Further, the thermoplastic material can be a polymer or a prepolymer.

The polymer comprises molecules comprising a sufficiently high amount of chemically bonded monomer units to exhibit chain entanglement, while the corresponding prepolymer does not have a sufficiently high number of identical chemically bonded monomer units to exhibit chain entanglement. In some embodiments, the thermoplastic material has a molecular weight of from about 3,000 to 100,000 g/mol, such as from 3,000 to 40,000 g/mol; more typically from 3,000 to 20,000 g/mol.

The reactive side chains and chain ends and their respective types/reactivity percentages are another parameter that controls the final properties of the particles such as crosslink density. In some embodiments, the reactive group can be an amine group or a phenol group or a derivative thereof, because it exhibits good reactivity to some of the crosslinking agents. The term "derivative" as used herein may have the ordinary meaning as is known to those skilled in the art and may include chemicals derived directly from another chemical or via modified or partially substituted. Thus, a compound which is envisaged to be substituted from one atom by another atom or atomic group and which is derived from the original compound can be regarded as a derivative of the original compound, and it can have the same or similar use as the original compound. Hydroxyl, epoxy, carbonyl, hydroxymethyl, glycidyl, anhydride, chloro, vinyl, vinyl ester, isocyanate, naphthyltetrahydro acid, acetylene, malay The quinone imines, phenolic compounds, benzoxazines, cyanate esters, dienyl groups, and the like are also reactive and provide a wide range of reactivity with different crosslinkers. Thus, the reactive group can be one or more of the following: an amine, a hydroxyl group, an acid anhydride, a glycidyl group, a carboxylic acid, a maleimide, an isocyanate, a phenolic compound, a bridged methylene tetrahydrophthalene. Nadimide, cyanate, acetylene, ethylene, vinyl ester, diene, or the like. In some cases, the unsaturation on the polymer chain can be used as a crosslinking point (in the case of acrylic and methacrylic acids and some unsaturated rubbers, vinyl esters or unsaturated polyesters).

In some embodiments, the number of reactive groups per chain may be at least 1 reactive group and, in some embodiments, is considered to be the minimum ratio required to establish a linked polymer backbone; Or a value greater than 1.5 to make a tightly crosslinked polymer or interpenetrating network. Polymers having a functionality greater than 2 will readily produce highly reactive gels.

The term "engineered crosslinked thermoplastic particles" as used in the present invention may have a general meaning as is known to those skilled in the art and may comprise a plurality of polymer chains comprising a thermoplastic polymer backbone, the thermoplastic polymer backbone comprising One or more thermoplastic polymers having one or more reactive groups, and a crosslinker chemically reactive with the reactive groups such that the crosslinker causes the polymer chain to pass through the reactive group Connected together. The engineered crosslinked thermoplastic particles may alternatively comprise a plurality of polymer chains comprising a thermoplastic polymer backbone having one or more thermoplastic polymers, and may be comprised of one or more compounds comprising one or more reactive groups The reactive group is chemically reacted and crosslinked by a crosslinking agent of a reactive group polymerization chemical, thereby forming an IPN. In certain embodiments, the crosslinked network is present in an amount ranging from 1 to 99% by weight of the total particles. In other embodiments, the range can be from 1 to 50% by weight of the total.

In some embodiments, the engineered crosslinked thermoplastic particles are thermodynamically compatible with the thermosetting resin. In other embodiments, the engineered crosslinked thermoplastic particles are substantially insoluble in the thermosetting resin. However, the engineered crosslinked thermoplastic particles can be expanded in an uncured thermosetting resin precursor. When a specific starting temperature specific to the particle characteristics is reached and exceeded, the particles present in the thermosetting resin begin to swell due to absorption of the resin monomer and oligomer material. If the particles are excessively expanded at a low temperature, such as the temperature at which the particles are mixed with the resin, the viscosity is increased, so that the fibers (e.g., carbon fibers) are difficult to be impregnated by the resin/particle combination. In some embodiments, the resin/particle combination is heated to a temperature above the blending temperature to allow the resin to diffuse into the particles. The absorbed monomer then reacts within the particles during uniform curing of the resin. Thus, the term "substantially insoluble" does not exclude that the particles are swellable when present in the resin. "Substantially soluble" includes the formation of a substantially homogeneous combination.

In some embodiments, the crosslinked particles for interlayer toughening have a monomer that is in good compatibility with, for example, an epoxy resin and is insoluble due to chemical crosslinking. In one embodiment, the particles comprising a copolymer based on PES (polyether oxime) and PEES (polyether ether oxime) repeating units exhibit an epoxy system, and in particular by, for example, 4,4'-diaminobisbenzene Excellent compatibility of the aromatic amine curing agent based on DDS.

The degree of crosslinking in the granules can be determined using tests such as sol/gel ratio and degree of swelling in the monomeric epoxy resin, as described in detail in the examples below.

In one embodiment, the thermoplastic particles do not comprise an elastomer or rubber. In other embodiments, a gradient interface is formed when the engineered crosslinked thermoplastic particles are formulated with a thermosetting resin such as an epoxy resin.

The engineered crosslinked thermoplastic particles may have an average particle size of from about 1 to 100 μm; typically about 40 μm prior to curing of the composite. They are substantially spherical in shape. As the particles expand, the particle size in the final cured product increases. The average cured particle size of the final cured particles in certain embodiments can range from about 5 [mu]m to about 40 [mu]m.

The term "crosslinking agent" as used herein may have any meaning as is known to those skilled in the art and may include any agent that can react with a functional/reactive group and promote crosslinking. In some embodiments, the crosslinker has a reactivity greater than two. In other embodiments, the crosslinker can be miscible with the thermoplastic polymer backbone. In other embodiments, for example, when the reaction is carried out in a solution using a common solvent for the thermoplastic polymer and the crosslinking agent, the crosslinking agent is not miscible with the thermoplastic polymer. Examples of suitable thermoplastic polymers that are readily crosslinkable in the context of the present application include, but are not limited to, polyether oxime (PES) having a hydroxyl end, polyether quinone having a hydroxyl end, an amine end or an anhydride end ( PEI), polyphenylene ether with hydroxyl end (PPO or polyphenylene ether PPE), polyaryl ether ketone with fluorine or hydroxyl end (including PAEK, PEEK, PEKK) or reactive terminal group or backbone function Any engineered polymer. Depending on the chemical nature of the polymer end groups/functionalities, suitable polyfunctional crosslinkers can be selected. Examples of such crosslinking agents are: alkylated melamine derivatives (e.g., Cymel 303), mercapto chloride (e.g., 1,3,5-benzenetricarbonyl trichloride), polyfunctional epoxides. (for example, MY0501, MY721), carboxylic acid (1,2,4,5-phenyltetracarboxylic acid). The polyunsaturated thermoplastic polymer can also be readily crosslinked via free radical addition using heat, UV or other radiation curing techniques.

Examples of crosslinking agents include melamine derivatives widely used in the coatings industry, such as Cymel manufactured by Cytec Industries. 350, which has an average of about 4.4 reactive sites; highly methylated melamine resin, such as Cymel manufactured by Cytec Industries 303, which has an average of about 4.9 reactive positions and has the following structure:

Highly alkylated glycoluril resin such as Cymel manufactured by Cytec Industries 1170, which has an average of about 2.9 reactive positions and has the following structure:

a resin containing tetrakis (methoxymethyl) glycoluril, such as Powderlink 1174 resin having an average of about 3.25 reactive positions, chemical name imidazo[4,5-d]imidazole-2,5-(1H,3H)-dionetetrahydro-1,3,4,6- Tetrakis(methoxymethyl) and has the following structure:

Other crosslinking agents suitable for use in the present invention include, but are not limited to, epoxy curing agents and ethylene terminated styrene-butadiene rubber (SBR). Specific types of crosslinking agents that are particularly suitable for utilizing the particles of the present invention include, but are not limited to, ARALDITE (acquired from Hunstman Co.), HYPRO And EPALLOY (acquired from Emerald), ANCAMINE (from Air Products and Chemicals), CYMEL (acquired from Cytec Engineered Materials), EPON And HELOXY (from Hexion), DE>R. And DEN (from Dow) and its combinations.

In particular embodiments, the ratio of crosslinker to thermoplastic backbone can be between about 2 and about 15 weight percent, such as between about 4 and about 13 weight percent, of the formulation. Typical amounts of crosslinker are from about 6 to 8% of the total amount of the formulation. For other types of crosslinkers, the ratio of crosslinker to thermoplastic backbone can vary and can be determined by those skilled in the art using only routine experimentation.

Engineered crosslinked thermoplastic particles can be made using a catalyst for the crosslinking reaction. The term "catalyst" as used herein may have the meaning as known to those skilled in the art and may include an acid catalyst such as p-toluenesulfonic acid, or a Cycat such as that produced by Cytec Industries. 500 strong sulfonic acid catalyst. In another embodiment, the catalyst can include triphenylphosphine.

In another aspect, the invention provides a method of making the engineered crosslinked thermoplastic particles described in detail herein. In a particular embodiment, the method comprises drying an emulsion comprising a thermoplastic polymer, a crosslinking agent or a component for crosslinking the network, and a catalyst and curing the dried powder. The method also includes dissolving a thermoplastic polymer, a crosslinking agent or a component for forming a crosslinked network, and a catalyst in a solvent which is immiscible with a second solvent (eg, water) in the presence of a stabilizer. And then made into an emulsion. Thus, in a particular embodiment, the solvent includes, but is not limited to, dichloromethane, chloroform, methanol, toluene, and the like. In a particular embodiment, the method further comprises stripping the solvent from the emulsion. Stripping can be by any means known to those skilled in the art, including, for example, by gas, distillation, vacuum, or the like. In particular embodiments, stabilizers can include, but are not limited to, ionic surfactants, nonionic surfactants, polymeric colloids, polymers, and combinations thereof. In a particular embodiment, the stabilizer is a polyvinyl alcohol. In other embodiments, the stabilizer is a hydroxycellulose (e.g., hydroxymethylcellulose or hydroxyethylcellulose). The reaction conditions and the type and amount of crosslinker will determine the final properties of the particles. Reaction conditions such as temperature will result in greater cross-linking. Crosslinkers having greater functionality will affect the degree of crosslinking of the thermoplastic particles. Crosslinkers having relatively low functionality will crosslink to a lesser extent. The crosslinker concentration is also directly proportional to the degree of crosslinking.

The method of making the particles described herein can further comprise washing, drying, grinding, and/or sieving the particles in any order. Those skilled in the art will appreciate that such steps are performed by a variety of methods known in the art and/or practiced using only routine experimentation.

The terms "matrix", "resin" and "matrix resin" as used herein have the ordinary meaning as known to those skilled in the art and may include one or more compounds comprising a thermosetting material. The engineered crosslinked thermoplastic particles can be combined with a thermosetting resin such as an epoxy resin, which can be used to make composite materials. In a particular embodiment, the particles may be present in an amount from about 1 to 50% by weight of the total resin system. In other embodiments, the particles may be present in an amount from 5 to 15% by weight. The term "thermosetting resin" as used herein has the general meaning as known to those skilled in the art and may include epoxy resins, quinone imine resins (eg, polyimine resin (PMR15), bismaleimide resin). (BMI)), cyanate ester, benzoxazine, phenol-formaldehyde resin, epoxy-acrylate and epoxy-methacrylate, polyester resin, vinyl ester resin, combinations thereof, and the like thereof . In some embodiments, the thermosetting resin comprises a monomer and/or a low molecular weight liquid that, when heated and has a low viscosity, operatively crosslinks the thermoplastic particles to absorb the resin and swell. In some embodiments, the resin will cure in the granules. In some embodiments, the resin can cause the engineered crosslinked thermoplastic particles to swell.

The term "curing" as used herein has the general meaning as known to those skilled in the art and includes polymerization and/or crosslinking processes. Curing can be carried out by methods including, but not limited to, heating, exposure to ultraviolet light, electron beam, and exposure to radiation. The matrix may further comprise one or more compounds in liquid, semi-solid, crystalline solid, and combinations thereof at about room temperature prior to curing. In other embodiments, the substrate within the prepreg film may be partially cured to exhibit selected adhesion or staple and/or flow characteristics. The curing process used to make the particles described herein can be carried out at 20 ° C to 300 ° C for 1 to 48 hours.

The combination of engineered crosslinked thermoplastic particles with the resins described herein can be used to make prepreg films. Furthermore, the engineered crosslinked thermoplastic particles of the present invention can be used in liquid forming processes such as injection molding. The term "prepreg" as used herein has a fibrous sheet or layer that is generally known to those skilled in the art and thus includes at least a portion of the volume impregnated via a matrix material. The matrix may be present in a partially cured state.

The term "fiber" as used herein has the general meaning as is known to those skilled in the art and may include one or more fibrous materials suitable for use in the reinforced composite. The fibers can be in the form of any of a combination of particles, flakes, whiskers, staple fibers, continuous fibers, sheets, layers, and the like. The continuous fibers may further be unidirectional, multi-dimensional (e.g., two or three dimensional) non-woven, woven, knitted, stitched, entangled, and woven configurations, as well as vortex mats, felts, and short mat structures. The fabric fiber structure can comprise less than about 1000 filaments, less than about 3000 filaments, less than about 6000 filaments, less than about 12,000 filaments, less than about 24,000 filaments, less than about 48,000 filaments. Root filaments, a plurality of fabric cords having less than about 56,000 filaments, less than about 125,000 filaments, and greater than about 125,000 filaments. In other embodiments, the rope is secured as above by cross-rope stitching, weft stitching or a small amount of resin.

The fiber composition can vary according to demand. Examples of fiber composition may include, but are not limited to, glass, carbon, aromatic polyamide, quartz, basalt, polyethylene, polyester, polyparaphenylene benzobisoxazole (PBO), boron, tantalum carbide , polyamine, and graphite, and combinations thereof. In one embodiment, the fibers are carbon, glass fibers, aromatic polyamines, or other thermoplastic materials. The reinforcing fibers can be organic or inorganic. In addition, the fibers can include a woven fabric structure, including those in a continuous or discontinuous form.

The term "laminate" as used herein has the ordinary meaning as is known to those skilled in the art and may include one or more prepregs disposed adjacent to one another. In a particular embodiment, the prepregs in the stack can be configured in a direction in which they are aligned with each other. In yet another embodiment, the prepreg can be woven together with the threaded material as needed to inhibit relative movement of the same from the selected direction. In other embodiments, the "laminate" can comprise any combination of fully impregnated prepreg, partially impregnated prepreg, and perforated prepreg as described herein. The laminate can be fabricated by techniques including, but not limited to, hand lamination, automated tape lamination (ATL), advanced fiber placement (AFP), and winding. The laminate can then be cured, such as by autoclaving, to form a composite article wherein the particles of the present invention are positioned in the intermediate layer and provide improved toughness and failure tolerance of the composite article, as the particles remain discrete even after the curing process Particles.

In some liquid forming embodiments, the particles may be pre-dispersed in a preform containing resin-free fibers. The terms "preform" or "fiber preform" as used herein have the general meaning as is known to those skilled in the art and may include a collection of fibers such as unidirectional fibers and woven fabrics that are formed to receive a resin.

The selection of a suitable thermoplastic polymer ensures chemical compatibility (i.e., thermodynamic compatibility) with the surrounding thermoset matrix without the risk of the particles being dissolved in the resin. The chemical compatibility of the thermoplastic particles with the substrate promotes the diffusion of a controlled amount of liquid resin into the particles, greatly increasing the adhesion of the particles to the resin. The benefits of chemical compatibility are not obtained by dissolving or filtering the thermoplastic material into the resin, due to the cross-linking properties of the particles, as described in more detail below. In some embodiments, the resin can diffuse into the particles and not reverse so that the particles maintain their mechanical integrity during the blending and curing process of the resin. Maintaining a portion of the initial strength during mixing, processing, and curing of the prepreg film can form areas of enriched resin between the layers that are known to impart improved delamination resistance to the cured composite. Desorption and particle delamination are often observed in the absence of chemical compatibility between the contents (particles) and the matrix to impart a strong interface. The lack of compatibility often results in premature microcracking at the interface between the particles and the matrix.

Compatibility can be determined by determining or calculating the Hansen or Hildebrand solubility parameters of the polymer and resin, however such calculations or determinations are complex. Therefore, hot stage microscopy can be used. In this method, the particles are mixed with different types of resins and subsequently heated under a microscope to determine if the particles interact or swell with the resin. In this method, the resin is heated to about 120 ° C to about the lowest viscosity point. In addition, the diffusion rate increases with temperature based on Arhenius. This is used to reduce time, but is also used to better simulate the real conditions during the curing process.

Another benefit of embodiments of the present invention is that localized high concentration of thermoplastic material can be obtained in the interlayer region without the risk of facing an inverted system. It is known that the amount of thermoplastic material in the interlayer region increases the toughness of the material. However, when a large amount of linear compatible thermoplastic material is blended or dissolved in a thermosetting resin, it is known that the thermoplastic material is phase-separated in an inverted manner during curing of the resin, which is also referred to as phase separation caused by the reaction, and is formed to contain A thermoplastic continuous phase of a thermoset polymer. This phase inversion is extremely detrimental to the properties of the composite, and is mainly detrimental to temperature resistance and solvent resistance. Embodiments of engineered crosslinked thermoplastic particles do not cause phase inversion. A high thermoplastic content can be obtained, so that the temperature resistance or solvent resistance of the material is not compromised.

In the composite, the engineered crosslinked thermoplastic particles can achieve higher local concentrations without being inverted as non-crosslinked thermodynamically compatible counterparts. For example, the local concentration of the engineered crosslinked thermoplastic particles in the interlayer region may be from about 10 to 50 weight percent of the resin composition. "Local concentration" is a certain term and refers to the weight or volume ratio of the components in the interlayer region. The interlayer region is a composite portion of a composite material comprising a region enriched in a resin between layers of fibers such as carbon fibers. Local concentrations can be obtained without inversion or without forming a thermoplastic material having a thermoset content. In some embodiments, the composite structure is a thermoset material having a thermoplastic content.

In some embodiments, the temperature resistance of the composite is about 80 to 350 °C. Conventionally, temperature resistance is determined by measuring the modulus of the decrease with increasing temperature (using, for example, dynamic mechanical thermal analysis or DMTA) or by measuring the glass transition temperature of the material by differential scanning calorimetry. In other embodiments, the solvent resistance of the composite is about 0 to 15%. Conventionally, solvent resistance is determined by measuring the weight absorption of a solvent over time.

Some embodiments of the present invention are based on the design of a gradient strong interface between the particles and the surrounding matrix, which utilizes a crosslinked thermodynamically compatible thermoplastic material to prevent dissolution while allowing it to expand in the resin. The term "gradient interface" as used herein has a general meaning as is known to those skilled in the art and refers to a strong gradient interface between the particles and the surrounding resin matrix. The gradient interface is achieved using engineered crosslinked thermoplastic particles that are dynamically compatible with the resin. As shown in Figures 1A and 1B, the concentration of the thermoplastic material in the core of the thermoplastic pellet containing the resin is greatest at the center and decreases toward the outer surface of the particle because the matrix enters from the outer surface and moves toward the core. A decrease in the concentration of the thermoplastic material from the core to the outer surface of the thermoplastic particles creates a gradient interface between the thermoplastic particles and the surrounding resin. Therefore, there is no significant profile or sharp transition between the thermosetting resin and the thermoplastic particles. If there is a sharp profile or a sharp transition, the interface between the thermoplastic material and the thermoset resin in the composite is much weaker than the composite containing the gradient interface.

In a particular embodiment, the particles are fully expanded, and thus the gradient characteristics in or throughout the particles become near zero. The particles are no longer thermoplastic or thermoset. The result can occur in loosely crosslinked particles or in low viscosity and thermodynamically close to the polymer. During the curing of the thermosetting resin, the particles will have time to fully expand due to the rapid diffusion of the low molecular weight resin.

In other embodiments, the particles include "layered particles" such as, but not limited to, a core-shell structure in which the expansion capabilities of the layers are independently controlled during the manufacture of the particles. In some embodiments, the layers may expand to varying degrees compared to adjacent layers.

"Thermodynamic compatibility" can be obtained by using a crosslinked thermoplastic material to prevent it from being dissolved into the matrix, but allowing it to swell in the resin. If fully homogenized during the preparation of the composite, the thermoplastic material will be soluble in the resin. Thus, in some embodiments, the thermoplastic particles are prevented from being completely homogenized during the preparation of the composite. Although in some cases it is predictable whether the thermoplastic particles are compatible with the resin, the method of testing whether the thermoplastic particles are thermally compatible with the resin is by combining the particles with the resin to determine whether the resin expands the particles rather than dissolves them and prepares The material is cured to determine whether the particles are maintained as discrete particles after curing. Examples of thermoplastic particles that are thermodynamically compatible with the epoxy resin but do not dissolve upon crosslinking include, but are not limited to, polyetherimine, polyfluorene, and polyether oxime.

The term "discrete particles" as used herein has the general meaning as is known to those skilled in the art and includes that it can be observed in interlaminar regions and can be utilized with scanning electron microscopy (SEM), optical microscopy, differential interference contrast microscopy (DIC). ) Detected particles.

Another advantage of this enhanced gradient interface is the effective transfer of stress between the particles and the surrounding matrix. Stress transfer capability refers to the most complete toughening characteristics of the particles. Many complex principles have been identified in the past, many of which assume that the stresses entering the material are transferred to the particles so that the plastic deformation and other energy loss principles can work effectively. In addition, insufficient stress transfer can also cause a decrease in matrix stiffness and strength, and can also be considered as a decrease in the elastic modulus of the matrix.

A composite comprising engineered crosslinked thermoplastic particles provides effective transfer stress between the particles and the surrounding resin matrix. The stress transfer capability can be determined by photoelasticity.

Another benefit of engineered crosslinked thermoplastic particles is improved life cycle performance compared to composites having different particles or no engineered crosslinked thermoplastic particles. Although conventional resins doped with a high concentration of phase-separated non-crosslinked thermoplastic materials may crack or microcrack after repeated heat or mechanical ringing, the resin modified by cross-linking particles may make the anthracene ring test more stable. Due to the cross-linking properties of the particles and the presence of thermosetting resins in the particles.

Composites containing engineered crosslinked thermoplastic particles have improved mechanical properties such as post-collision compression (CAI) or (CSAI) fracture toughness or delamination resistance of modes I and II (G _IC and G _IIC ) OHC (through-hole) compression). CAI (or CSAI) measures the ability of a laminate/composite to resist damage. According to this method, the laminate to be tested is impacted via a predetermined energy and subsequently subjected to compression. The laminate was constrained during the test to ensure inelastic instability. Record the strength of the laminate. The first thing to note about the benefits of interlaminar toughened particles is the material properties for cracking, such as CAI, G _IC and G _IIC , K _IC and K _IIC as described in Examples 22 to 23 below. The K _C and G _C characteristics represent fracture toughness, which characterizes the ability of a material containing a crack to resist cracking. K represents the stress density factor and G is the fracture energy. K _IC can be based on the ISO standard "Plastics--Determination of fracture toughness (G _IC and K _IC )--Linear elastic fracture mechanics (LEFM) approach (ISO 13586: 2000)" or according to the method recommended by the ESIS Committee, "Fracture Mechanics Testing Methods for Polymers Adhesives and Composites, DR Moore, A. Pavan, JG Williams, ESIS Publication 28, 2001, pp. 11-26.

In some embodiments, a high Tg (eg, at least 180 ° C Tg) composite is fabricated such that the neat resin material in the interlayer region can have at least about 0.8 to about 3 MPa.m ^0.5 (typically between 0.9 and 1.1). K _IC , and G _{IC of} at least about 200 to about 500 J/m ² (typically about 250 J/m ² ).

In addition, the concept of performing particle toughening can be employed in other fields of demand for toughening, including, but not limited to, adhesive formulations, first and second structural thermoset formulations.

The K _IC and G _{IC of the} cured resin can be determined by linear elastic fracture mechanics (LEFM) as described in more detail in Example 22.

In one aspect, the resin modified by engineering crosslinked thermoplastic particles is tested via an anthracene ring. This test involves the presence of a composite comprising a modified resin via repeated heat or mechanical loops and subsequent determination of the presence of cracks or microcracks. The determination of the presence and extent of microcracks is generally performed by SEM analysis, and the number of visible microcracks per unit length is recorded.

Another advantage of using crosslinked particles includes the ability to tailor their crosslink density, such as by varying the crosslinker concentration and the degree of crosslinking in the particles, which can also tailor the coefficient of expansion of the particles. . This customization capability is important when considering the variables of the resin consisting of a blend of monomers that can interact differently with the thermoplastic particles. The ability to easily customize particle characteristics provides a powerful tool for resin blenders and also ensures complete use of toughened particles. For example, as the particle expansion increases, the thermoplasticity imparted to the composite material decreases.

Therefore, methods for tailoring particle characteristics to achieve various characteristics and specific epoxy resin formulations are also contemplated. The method for customizing the characteristics of the particles comprises the steps of determining the rate and extent of diffusion of a particular resin formulation, and subsequently evaluating the appropriate particle crosslink density to specifically match the formulation.

The terms "approximately", "about" and "substantially" as used herein mean an amount that is close to the quantity that still exhibits the desired function or obtains the desired result. For example, "approximate", "about" and "substantially" may mean an amount within 10% less than the stated amount, less than 5%, less than 1%, less than 0.1%, and less than 0.01%. The term "at least a portion" as used herein means the amount of the total amount of the total amount. For example, the term "a portion" may mean greater than 0.01%, greater than 0.1%, greater than 1%, greater than 10%, greater than 20%, greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 70%, greater than 80%, greater than 90%, greater than 95%, greater than 99% or an amount of 100% of the total.

Other embodiments

An engineered particle comprising:

a) a plurality of polymer chains comprising a thermoplastic polymer backbone comprising one or more thermoplastic polymers and one or more reactive groups;

b) a crosslinking agent which is chemically reactive with the one or more reactive groups, wherein the crosslinking agent causes the polymer chains to directly crosslink each other via the reactive groups.

2. An engineered particle comprising:

a) a plurality of polymer chains comprising a thermoplastic polymer backbone comprising one or more thermoplastic polymers;

b) a crosslinked network comprising a crosslinker having one or more reactive groups and one or more chemical groups capable of polymerizing the chemical species by the reactive groups, wherein (a) and (b) Together form an interpenetrating polymer network.

3. The engineered particle of embodiment 2, wherein the polymer chains each have one or more reactive groups.

4. The engineered particle of any of embodiments 1 to 3, wherein the one or more reactive groups are at the terminus.

5. The engineered granule of any one of embodiments 1 to 4, wherein the thermoplastic polymer chain is selected from the group consisting of: polycarbonate; polyether quinone imine; polyamidamine; polyimine; polyfluorene; Polyether oxime; polyethylene oxide; polyether ketone; styrene-butadiene; polyacrylate; polyacetone alcohol; polybutylene terephthalate; polyamine-quinone imine; polyhydroxy ether; Polyphenyl sulfide; polyoxyalkylene; copolymers thereof; and the like.

6. The engineered granule of any one of embodiments 1 to 5, wherein the thermoplastic polymer chain is selected from the group consisting of polyphenylene oxide-polystyrene alloy and toughened polyphenylene oxide; Polyether quinone imine; toughened polyimine and its combinations.

7. The engineered particle of embodiment 6, wherein the plurality of chains comprising one or more thermoplastic polymers are selected from the group consisting of: ULTEM ;NORYL ;SILTEM ; and EXTEM Brand polymer.

8. The engineered granule of any of embodiments 1 to 7, wherein the thermoplastic material is present in an amount from 1 to 99% by weight of the total granule.

9. The engineered particle of any one of embodiments 1 to 8, wherein the reactive group is selected from one or more of the group consisting of: a vinyl group; an amine group; an epoxy group; a hydroxyl group; a carboxylic acid; Chlorine; isocyanate; bridged methylene tetrahydrophthalic acid; acetylene; maleimide; vinyl ester; benzoxazine; cyanate; phenolic compound;

10. The engineered particle of any one of embodiments 2 to 9 wherein the crosslinking agent is selected from the group consisting of: vinyl terminated styrene-butadiene-rubber; ARALDITE ;HYPRO ;ANCAMINE ;CYMEL ; EPON ;DEN ;DER ;EPALLOY ;HELOXY ; and ANCAMIDE Brand polymer; and other combinations.

11. The engineered particle of any of embodiments 2 to 10, wherein the crosslinked network is present in an amount ranging from 1 to 99% by weight of the total particles.

12. The engineered granule of embodiment 11, wherein the range is from 1 to 50% by weight of the total granules.

13. The engineered particle of any of embodiments 2 to 12, wherein the interpenetrating network is a semi-interpenetrating network.

14. The engineered granule of any of embodiments 1 to 13, wherein the average particle size is between 1 and 100, preferably between 1 and 40, more preferably between 5 and 40 microns.

15. A resin system comprising:

a) a thermosetting resin; and

b) A plurality of engineered crosslinked particles according to any one of embodiments 1 to 14, wherein the particles are partially or completely insoluble in the resin during curing.

16. The resin system of embodiment 15, wherein the resin is selected from one or more of the following thermoset systems: epoxy; bismaleic anhydride; polyimine; isocyanate; phenolic; vinyl ester; Oxazine.

17. The resin system of any one of embodiments 15 to 16, wherein the particles are present in an amount from 1 to 50% by weight of the total resin.

18. The resin system of embodiment 17, wherein the amount of the particles is from 5 to 15% by weight.

19. A prepreg comprising the engineered particles of any of embodiments 1 to 14 or the resin system of any of embodiments 15 to 18.

20. A composite article comprising the engineered particles of any of embodiments 1 to 14 or the resin system of any of embodiments 15 to 18, wherein the particles are still discrete particles after the curing process, and Wherein the particles are located in the intermediate layer and provide improved toughness or failure tolerance of the composite.

21. The composite article of embodiment 20, further characterized by one or more of the following:

i) reduced solvent sensitivity;

Ii) improved heat/humidity properties/characteristics;

Iii) improved processing characteristics; and

Iv) resistance to microcracking.

22. A method of making an engineered particle according to any of embodiments 1 to 14, the method comprising:

a) dissolving the thermoplastic polymer chains and the crosslinking agent or components of the crosslinking network, if present, in a solvent;

b) forming an emulsion by mixing the solution of step (a) with a second solution in the presence of one or more stabilizers, the second solution being immiscible with the one formed in step (a);

c) stripping the solvent into the emulsion of step (b), thereby forming a plurality of solid particles;

d) curing the solid particles thereby directly crosslinking the particles or forming an interpenetrating polymer network.

23. The method of embodiment 22, further comprising one or more of the following:

i) cleaning the particles;

Ii) drying the particles;

Iii) grinding the particles; and

Iv) Screening the particles.

The method of any one of embodiments 22 to 23, wherein the emulsion is in the form of an oil-in-water or water-in-oil.

The method of any one of embodiments 22 to 24, wherein the curing step is carried out by a method selected from the group consisting of heating; radiation; electron beam; and UV light.

The method of any one of embodiments 22 to 25, wherein the solvent is selected from one or more of the group consisting of dichloromethane, chloroform, methanol, toluene, and the like, and the second solution thereof Water.

27. The method of any one of embodiments 22 to 26, wherein the stabilizer is selected from the group consisting of: an ionic surfactant; a nonionic surfactant; a polymer colloid, a polymer; and combinations thereof.

The method of any one of embodiments 22 to 27, wherein the stabilizer is selected from the group consisting of polyvinyl alcohol, hydroxy cellulose; hydroxymethyl cellulose; and hydroxyethyl cellulose.

29. The method of any one of embodiments 22 to 28 wherein the solvent is stripped by gas, distillation, or vacuum.

The method of any one of embodiments 22 to 29, wherein the curing step is carried out at 20 ° C to 300 ° C for 1 to 48 hours.

The method of any one of embodiments 22 to 30, wherein step (a) further comprises dissolving the catalyst.

32. A method of making a composite article having improved toughness and damage tolerance, the method comprising:

a) adding particles obtained according to any one of embodiments 1 to 14 or according to any one of embodiments 22 to 31 to a thermosetting resin system;

b) forming a plurality of prepreg films by the resin system of step (a);

c) laminating the prepregs to form a shaped article, wherein the engineered particles are in the intermediate layer;

d) curing the article, thereby forming a composite article having improved toughness and failure tolerance.

Instance

The following examples are provided to assist those skilled in the art to further understand the specific embodiments of the invention. The examples are intended to be illustrative only and are not to be construed as limiting the scope of the invention.

The methods of making the various embodiments of the engineered particles of the present invention are exemplified below. In general, the engineered crosslinked thermoplastic particles of the present invention can be prepared in an emulsification process by dissolving a component of a polymer, a crosslinking agent or a crosslinking network, and a catalyst in a common solvent. Not miscible with water. The emulsion is then made in water by using a nonionic surfactant.

The emulsified granules are then dried and cured to form a chemical 3D network by chemically crosslinking or bundling the polymer chains while forming a separate and independent crosslinked network while simultaneously rendering them insoluble.

The reaction conditions and type and amount of crosslinker or crosslinked network will determine the ultimate characteristics of the particles described herein.

When blended in a thermosetting resin, once the resin temperature exceeds a specific starting temperature (which is specific to the particle characteristics), the particles begin to swell due to absorption of the monomeric species. During the regular curing of the resin, the absorbed monomer is subsequently reacted in the particles.

This method results in particles of a thermoplastic-rich material that exhibits gradient composition characteristics at the interface. This engineered interface exhibits improved interface adhesion characteristics. Figures 1A and 1B depict particle property evaluation after matrix monomers have diffused into the particles. The highly crosslinked particles (Fig. 1A) and the looser crosslinked particles (Fig. 1B) were compared. The x-axis represents the distance from the core particles and the y-axis represents the concentration of the thermoplastic material. Thus, Figure 1A includes a higher concentration of thermoplastic material in the core of the higher height crosslinked particles, while Figure 1B depicts the lower thermoplastic concentration in the core of the lower height crosslinked particles.

Embodiments of the engineered particles of the present invention can be characterized by two main tests: the sol/gel ratio and the degree of expansion in the monomeric epoxy resin.

The first test is a simple method of evaluating the amount of chemically crosslinked polymer in the granules. A known amount of particles is mixed into a suitable solvent, i.e., dichloromethane for the PILT-100 particles, and filtered to determine the gel fraction of the particles. A typical value was found to be about 70%. In general, the particles were found to be in the range of 50 to 99%.

The second test measures the ability of the particles to absorb monomeric resins such as epoxy monomers. The standard method consists of observing the expansion behavior of a group of about 10 particles blended in a low viscosity epoxy resin such as MY0510 while heating the resin to a high temperature. The particle diameter when fully expanded by the monomer is compared with the original particle diameter and the expansion coefficient is calculated. For practical reasons, it is often expressed as "interactive expansion," that is, Di/Df. The coefficient of expansion of the particles can be tailored by varying the concentration of the crosslinker and thus the degree of crosslinking in the particles. This is described in the graph of Figure 2.

Comparative example 1

Comparative Example 1 is an emulsified granule of pure Ultem 1000 which is used as a comparative material.

500 grams of Ultem 1000 (SABIC-IP) was dissolved in 1500 grams of dichloromethane. This solution was pumped under high shear into a vessel containing 5000 grams of water pre-dissolved with 225 grams of polyvinyl alcohol (Celvol 203 from Celanese). After the emulsion is formed, the solvent is removed through the emulsion by pumping nitrogen. When there was no condensation collection in the cooled collector, the dispersion containing the particles was diluted several times with water and filtered through a 40 micron screen. The granules were then dried under vacuum at 80 ° C, slightly ground and sieved. The particles thus obtained were numbered PEI-P#1.

Example 1

Example 1 uses a long chain rigid (ie, high _Tg ) polymer network to form a semi-IPN.

450 grams of Ultem 1000 and 142.86 grams of KM180 (Cytec) were dissolved in 2428 grams of dichloromethane. 7.14 grams of Araldite MY0510 (Huntsman Co) was added to the solution. After forming a homogeneous solution, the solution was pumped into a vessel pre-dissolved with 270 grams of Celvol 203 in 6750 grams of water. The solution was pumped under high shear for 30 minutes. After the emulsion is formed, the solvent is removed through the vessel by pumping nitrogen. When no condensate was collected in the cooling collector, the dispersion containing solid particles was diluted with water and filtered through a 40 micron sieve. The dilution was repeated 10 times and the particles were collected and dried under vacuum at 50 ° C for 12 hours. The pellets were cured at 220 ° C for 3 hours, slightly ground and sieved to obtain granules. The particles thus obtained were numbered PEI-P#3.

Example 2

Example 2 uses a long chain soft (ie, low _Tg ) polymer network to form a semi-IPN.

Example 2 utilized the same procedure as Example 1, using 450 grams of Ultem 1000, 135 grams of Hypro 1300 X16 from Emerald, and 15 grams of Araldite MY0510. The curing conditions were 170 ° C for 1 hour.

The particles prepared in Example 2 were numbered PEI-P#4.

Example 3

Example 3 uses a short chain rigid polymer network to form a semi-IPN.

Example 3 utilized the same procedure as Example 1, using 510 grams of Ultem 1000, 59 grams of Araldite MY0510, and 31 grams of Ancamine 2167. The curing conditions were 200 ° C for 1 hour.

The particles prepared in Example 3 were numbered PEI-P#5.

Example 4

Example 4 demonstrates the direct crosslinking of thermoplastic polymers to prepare particles having controlled swelling or insoluble in the formulation of the resin used in the manufacture of the composite.

Example 4 used the same procedure as Example 1, using 593.7 grams of C863759-6 (amino-terminated polyetherimine from Sabic-IP) and 6.3 grams of Araldite MY0510. The curing conditions were 230 ° C for 5 hours.

The particles prepared in Example 4 were numbered PEI-P#13.

Example 5

Example 5 demonstrates hybrid particles made with two thermoplastic polymers.

Example 5 utilized the same procedure as Example 1, using 300 grams of Noryl 853 (polyphenylene ether from Sabic-IP), 270.84 grams of KM180 (polyether oxime block copolymer from Cytec), and 29.16 grams of Cymel 350 (from Cytec's methylated melamine derivative). The curing conditions were 180 ° C for 3 hours.

The particles prepared in Example 5 were numbered XKM-PPO #2.

Example 6

Example 6 demonstrates the direct crosslinking of thermoplastic polymers to produce particles that are denser and less susceptible to microcracking.

Example 6 utilized the same procedure as Example 1, using 533.4 grams of Noryl MX90 (hydroxy terminated polyphenylene ether from SABIC-IP), 66 grams of Araldite MY0510, and 0.6 grams of triphenylphosphine (from Arkema). The curing conditions were 180 ° C for 2 hours.

Example 7

Crosslinking efficiency is determined by the degree of gelation of the particles using a sol-gel method. This test is a simple method of evaluating the amount of chemically crosslinked polymer in a granule. A known amount of the granules is mixed into a suitable solvent, for example, dichloromethane, and filtered to determine the gel fraction of the granules. A typical value was found to be about 70%. In general, the particles were found to be in the range of 50 to 99%.

In this method, a good solvent such as dichloromethane or chloroform is used for the thermoplastic material to dissolve the particles. After 24 hours of dissolution at room temperature, the mixture was filtered through a 0.5 micron filter. The filtered portion of the solution and the gel portion retained by the filter were sufficiently dried and weighed. If the solid in the solution is added to the dry gel to 100% +/- 5%, the assay is considered valid and the percentage of gel is recorded.

The gelation levels of some of the particles listed herein are listed in Table 1.

The results in Table 1 indicate that the degree of gelation varies widely depending on the technique and the crosslinking method used.

The effect of the degree of gelation on how many particles can maintain their shape is depicted in Figures 4A through D.

Example 8

The ability of the particles to remain insoluble is important to impart toughness to the composite. The toughness is usually measured industrially using post-collision compressive strength (CAI). The composite is made by depositing particles on a blank prepreg film that does not contain particles. The composite CAI was tested according to BSS 7260 - Model II Category I. The results are shown in Table 2.

From the CAI data in the table below, it is known that the use of Ultem 1000 as a soluble thermoplastic (TP) is far less efficient than its particulate form, and this method is verified by this.

The data in Table 2 indicates that retaining particle boundaries can greatly improve composite toughness. The data further indicates that the particles can be subjected to their equal toughening without causing microcracking problems.

Example 9

Another test system, G _{IIC, for} determining the fracture toughness of the composite. This was tested by placing a separation membrane between the intermediate layers 10 and 11. The test was carried out according to the test method BMS 8-276-Mode II. The results are shown in Table 3.

From the data in Table 3, it can be seen that the engineered particles can greatly improve the fracture toughness.

Example 10

The reliability of microcracking inferior materials in composite materials is due to the failure of parts due to repeated take-off and landing of aerospace tools. Microcracking can be observed under the microscope with the aid of fluorescent dyes. In our experiments, microcracks were qualitatively determined by Zyglo fluorescent dye using this microscopic method.

Polyphenylene ethers such as the Noryl series from SABI-CIP are effective toughened thermoplastics. However, such materials are prone to microcracking, even without a hot ring. Microcracking can be reduced or eliminated by hybridizing this material to other thermoplastic materials. Preliminary results are shown in Table 4.

Example 11

This example shows the application of the concepts and methods of the present invention to prepare interlayer toughened particles using a decane-modified polyether quinone imide as a thermoplastic material.

552.5 g of Siltem 1500 (SABIC-IP) was dissolved in 2210 g of dichloromethane. 63.93 grams of Araldite MY0510 (Huntsman Co) was added to the solution followed by 33.57 grams of Ancamine 2167 (Air Products). After forming a homogeneous solution, the mixture was pumped into a vessel containing 7020.0 grams of water pre-dissolved with 292.5 grams of Celvol 203. The mixture was pumped under high shear for 60 minutes. After the emulsion is formed, the solvent is removed through the vessel by pumping nitrogen. After the condensate was not collected in the cooling collector, the dispersion containing solid particles was diluted with water and filtered through a 40 micron sieve. The dilution was repeated 10 times and the particles were collected and dried under vacuum at 60 ° C for 12 hours. The pellets were cured at 180 ° C for 1 hour, slightly ground and sieved to obtain granules. The particles thus obtained were numbered STM#1.

Examples 12 and 13

Examples 12 and 13 utilized the same procedure as in Example 11 and used according to the formulations in the table below.

Hypro The 1300X16 is an ATBN supplied by Emerald Performance Materials.

It is apparent that the Siltem particles engineered according to the present invention significantly improve the properties of the composite.

Examples 14 and 15

Examples 14 and 15 demonstrate the use of the concepts and methods of the present invention to prepare interlaminar toughened particles using the modified polyimine as a thermoplastic material.

These examples utilized the same method as in Example 11 and used formulations according to the following table.

1. Extem XH1015 is a polyimine provided by SABIC-IP.

These examples show that engineered particles provide improved composite properties. It is worth noting that there are some differences between the selected thermoplastic materials.

Examples 16, 17, and 18 used polyphenylene ether (PPO) as the particles of the thermoplastic material. Since the PPO is insoluble in the composite resin formulation, such particles demonstrate that the concept of the present invention can be applied to materials which can be used as an interlayer particle toughening agent by itself.

Example 16

Example 16 is a granule prepared by an emulsification process and free of other chemical modifiers. This pellet is for reference purposes.

600 g of Noryl PPO 640 (SABIC-IP) was dissolved in 2929 g of chloroform. The solution was pumped into a vessel containing 6480 grams of water pre-dissolved with 270 grams of Celvol 203. The mixture was pumped under high shear for 60 minutes. After the emulsion is formed, the solvent is removed by applying a vacuum. The vacuum is stably increased during the process to avoid transitional foaming. When the condensate was not collected by the condensate collector, the dispersion containing solid particles was diluted with water and filtered through a 40 micron sieve. The filtration was repeated 10 times and the particles were collected and dried under vacuum at 60 ° C for 12 hours. It can be used after grinding the material slightly. The granules thus obtained were numbered EPPO-640.

Examples 17 and 18

Examples 17 and 18 utilized the same method as Example 16. The composition of the polymer solution is listed in the table below.

Ancamide 506 is a guanamine amine supplied by Air Products, Inc.

2.Hypro The 1300X31 is a CTBN supplied by Emerald Performance Materials.

It has been discovered that engineering the insoluble thermoplastic material using the concepts of the present invention improves the composite CAI and microcracking properties.

Examples 19 and 20

Examples 19 and 20 demonstrate the preparation of interlaminar particles that directly crosslink thermoplastic polymers using different functional groups to obtain crosslinks. Examples 19 and 20 used the same method as in Example 1. The particle composition and results are shown in Table 8. It is apparent that the crosslinked particles impart significantly higher toughness to the composite.

Example 21

The granules of the present invention can also be prepared according to the above method using the formulations given in Tables 8A to D below.

As shown below, Cymel 350 is a melamine derivative that reacts with hydroxyl and amine functional groups via a condensation mechanism. This molecule is characterized by its multiple reactive sites (average 4.4) required to establish a crosslinked network. This structure also shows the condensation of the first amine functional nucleophilic attack with the carbon adjacent to the methoxy group.

The reaction is further catalyzed by the introduction of an acid catalyst such as p-toluenesulfonic acid. The possible reaction mechanisms are shown below.

Several variations of the above formulations have been successfully tested. These include alternating use of crosslinkers and other catalysts.

real Example 22

Comparison of fracture resistance (toughness) and elastic modulus

The benefits of using particles with a gradient interface in pure resin by utilizing linear elastic fracture mechanics (according to the ESCS committee, "Fracture Mechanics Testing Methods for Polymers Adhesives and Composites", DR Moore, A. Pavan, JG Williams, ESIS Publication 28, 2001, pages 11 to 26 recommended methods) were confirmed. Pure resin samples (no fibers) were prepared by conventional thermal mixing techniques and cast into a mold for curing. K _IC and G _IC were determined by LEFM on pure resin, and the elastic modulus was determined by flexibility measurement.

The resin evaluated is described in detail as follows:

MY 0510 is a triglyceryl-p-aminophenol TGAP (Araldite MY 0510) available from Huntsman, The Woodlands, TX. PY 306 is a bisphenol F-type epoxy resin available from Huntsman, The Woodlands, TX. 44DDS is 4,4'-diaminodiphenyl hydrazine. HC99-based PES copolymer (available from Cytec Engineered Materials). PILT-100 is the nomenclature of crosslinked particles produced in accordance with the methods described herein.

Table 10D above shows that the particles can toughen the substrate without sacrificing the elastic modulus of the resin.

Example 23

Particle stiffness

The degree of crosslinking of the particles also ensures that the particles retain sufficient stiffness, including when they are expanded by the surrounding thermosetting resin, so that they can establish and maintain interlayer gaps. This behavior is depicted in Figure 3. Particles are visible in the region enriched in the resin, which divide the layer enriched in carbon fibers.

Example 24

Post-collision compression (CAI) and fracture toughness (G _IIC ) determination

Typical compound formulations are described below. The following example shows the difference in behavior of crosslinked particles PILT-100 with standard PPO (polyphenylene oxide) particles and rubber DP5045 particles in two different formulations.

MY721 was obtained from Ciba Geigy Corporation, Hawthorne, N. Y. Glycidyldiaminodiphenylmethane TGDDM (Araldite MY721). MY0610 is available from Ciba Geigy Corporation, Hawthorne, N. Y 3-glycidoxy-N,N-diglycidylaniline or triglycidyl m-aminophenol (Araldite MY0610). 33DDS is 3,3'-diaminodiphenyl hydrazine. PES 5003P is a phenol-based capped PES (5003P) available from Sumitomo Chemical Co. Ltd. (Osaka, Japan). PPO is a polyphenylene oxide thermoplastic particle (available from Sabic Innovative Plastics).

The rupture characteristics (CAI and G _IIC ) are shown in the composite to control the value of the compatible crosslinked particles at which crack initiation and growth occur.

More importantly, the chemical and mechanical resistance of engineered particles is far superior to existing thermoplastic materials. This result is exacerbated in samples used to test solvent sensitivity under stress. As shown in Figures 6A and B, conventional PPO thermoplastic particles begin to form microcracks, while crosslinked compatible particles exhibit much higher resistance to microcracking.

The compatibility of the particles with the matrix resin ensures that a gradient stress is established at the interface between the particles and the matrix, which controls the stress strength at the interface of the particles. The clear and steep interface found in conventional materials often leads to premature desorption of particles, which then evolve into material microcracks and early rupture. In addition, the cross-linking properties of the particles forming the polymer significantly increase their isotropic toughness and their resistance to microcracking and cracking.

Throughout this application, reference has been made to various patents and/or scientific documents. The disclosures of these publications in their entireties are hereby incorporated by reference in their entirety in the extent of the extent of the disclosure of the disclosure. In view of the above discussion and examples, those skilled in the art will be able to practice the invention as claimed without undue experiment.

While the above discussion has shown, described and illustrated the novel features of the present invention, it will be appreciated that those skilled in the art can various modifications and substitutions of the details of the device, and the like, without departing from the scope of the invention. And change. In the meantime, the scope of the present invention should not be limited by the above discussion, but should be limited by the scope of the appended patent application.

Figures 1A through B depict changes in particle characteristics after diffusion of matrix monomers into the particles. (A): describing higher-level crosslinked particles having a higher concentration of thermoplastic material in the core, and (B) describing lower-highly crosslinked particles having a lower concentration of thermoplastic material in the core;

Figure 2 depicts the coefficient of expansion of the crosslinker concentration to the particles;

Figure 3 depicts the interlayer gaps formed and obtained by the particles which retain sufficient stiffness, including when they are expanded by the surrounding thermosetting resin. Particles are visible in the resin-rich region, and the particles divide the carbon fiber-rich layer;

4A to D: The efficiency of crosslinking is as shown in the sol-gel method corresponding to Table 1. It is shown how much the gel concentration can maintain its shape for the extent to which the particles can. When the gel concentration is 0 (A), the particles will completely lose their equal limits during solidification of the composite. As the gel concentration increases, the boundaries of the particles become more and more clear (B-D);

Figures 5A to B: Microcracks were qualitatively determined by microscopy using a Zyglo fluorescent dye. (A): by polyphenylene ether (such as polyphenylene oxide Noryl obtained from Sabic-IP) 853) and no gels are microcracks as evidenced by particles prepared without a hot enthalpy ring; (B) by Noryl 853 and KM 180 (a polyether oxime block copolymer obtained from Cytec) and 21% by weight of the gel prepared hybrid particles proved to be free of microcracking;

Figures 6A-B show the inter-layer regions of the composite after testing for solvent resistance under strain; the microcracks are shown using fluorescent dyes. Figure 6A depicts the behavior of cross-linking compatible particles, and Figure 6B depicts the behavior of PPO-modified resins. Cracks were observed only on samples containing conventional thermoplastic particles.

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Claims (23)

An engineered crosslinked particle comprising: a) a plurality of thermoplastic polymer chains each comprising a thermoplastic polymer backbone; and b) by reacting a chemical having one or more reactive groups One or more reactive groups polymerize a crosslinked network resulting from a crosslinker of the chemical species, wherein the thermoplastic polymer chain forms an interpenetrating polymer network with the crosslinked network, and the thermoplastic polymer chain is The crosslinked network is entangled. The engineered crosslinked particles of claim 1, wherein the polymer chains each have one or more reactive groups. The engineered crosslinked particle of claim 1, wherein the one or more reactive groups are at the terminus. The engineered crosslinked particle of claim 1, wherein the thermoplastic polymer chain is provided by a thermoplastic polymer selected from the group consisting of: polycarbonate; polyether quinone; polyamine; polyfluorene Imine; polyfluorene; polyether oxime; polyphenyl oxide; polyether ketone; styrene-butadiene; polyacrylate; polyacetal; polybutylene terephthalate; polyamine-quinone imine Polyhydroxy ether; polyphenyl sulfide; polyoxyalkylene; copolymers thereof; and the like. The engineered crosslinked particles of claim 1, wherein the reactive groups are selected from the group consisting of: vinyl; amine; epoxy; hydroxyl; carboxylic acid; anhydride; glycidyl; chloro; isocyanate; Tetrahydrophthalate Nadimide; acetylene; maleimide; vinyl ester; cyanate; dienyl and phenolic. The engineered crosslinked particle of claim 1, wherein the crosslinking agent is selected from the group consisting of: a vinyl terminated styrene-butadiene rubber; an alkylated melamine derivative; a mercapto chloride; a polyfunctional ring Oxide; carboxylic acid and combinations thereof. The engineered crosslinked particles of claim 1, wherein the crosslinked network is present in an amount ranging from 1 to 50% by weight of the total particles. An engineered crosslinked particle of claim 1, wherein the particle size is between 1 and 100 microns. A resin system comprising: a) a thermosetting resin; and b) a plurality of engineered crosslinked particles of claim 1, wherein the particles are expandable in the cured thermosetting resin. The resin system of claim 9, wherein the thermosetting resin is one or more selected from the group consisting of epoxy; bismaleic anhydride; polyimine; cyanate; phenolic; vinyl ester; And oxazine. The resin system of claim 9, wherein the amount of the particles is from 5 to 15% by weight. A prepreg comprising reinforcing fibers; a thermosetting resin; and a plurality of engineered crosslinked particles as claimed in claim 1. A composite article comprising a layer of reinforced fiber impregnated with a thermosetting resin and a layer of a plurality of engineered crosslinked particles of claim 1, wherein the particles are located in an interlayer region between the layers of reinforcing fibers. A method of producing an engineered crosslinked particle according to claim 1, the method comprising: a) a thermoplastic polymer, a chemical having one or more reactive groups, and one or more reactive groups a crosslinking agent that polymerizes the chemical substances is dissolved in a solvent to form a solution; b) an emulsion is formed by mixing the solution of the step (a) with the second solution in the presence of one or more stabilizers, the second solution and the step (a) the former is immiscible; c) the solvent is stripped of the emulsion of step (b), thereby forming a plurality of solid particles; and d) solidifying the solid particles, thereby forming an interpenetrating polymer network . The method of claim 14, further comprising one or more of: i) washing the particles; ii) drying the particles; iii) grinding the particles; and iv) sieving the particles. The method of claim 14, wherein the emulsion is in the form of an oil-in-water or water-in-oil. The method of claim 14, wherein the curing step is performed by a step selected from the group consisting of: heating; irradiation; electron beam; and UV light. The method of claim 14, wherein the solvent is selected from one or more of the group consisting of dichloromethane, chloroform, methanol, toluene, and the like, and wherein the second solution is water. The method of claim 14, wherein the stabilizer is selected from the group consisting of: an ionic surface Active agent; nonionic surfactant; polymer colloid, polymer; and combinations thereof. The method of claim 14, wherein the stabilizer is selected from the group consisting of polyvinyl alcohol, hydroxy cellulose; hydroxymethyl cellulose; and hydroxyethyl cellulose. The method of claim 14, wherein the solvent is stripped by gas, distillation, or vacuum. The method of claim 14, wherein the curing step is carried out at a temperature of from 20 ° C to 300 ° C for from 1 to 48 hours. The method of claim 14, wherein step (a) further comprises dissolving the catalyst.