WO2022010622A1

WO2022010622A1 - Processes for making 3-d objects from blends of polyethylene and polar polymers

Info

Publication number: WO2022010622A1
Application number: PCT/US2021/037387
Authority: WO
Inventors: Ru XIE; Ying Ying SUN
Original assignee: Exxonmobil Chemical Patents Inc.
Priority date: 2020-07-07
Filing date: 2021-06-15
Publication date: 2022-01-13

Abstract

This invention relates to a process for making a three-dimensional object using an additive manufacturing process. A blend is prepared that includes polyethylene having a density of at least 0.94 g/cm3 and a polar polymer. The blend is extruded to make a filament. The filament can be inserted into an additive manufacturing apparatus that has a nozzle. The filament can be heated. A fluid bead of the filament is dispensed out of the nozzle to manufacture a three- dimensional object.

Description

TITLE: Processes for Making 3-D Objects from Blends of Polyethylene and Polar Polymers

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to USSN 63/048982, filed July 7, 2020, herein incorporated by reference.

FIELD [0002] This invention relates to additive manufacturing. More particularly, this invention relates to using an additive manufacturing process such as fused filament fabrication to make 3-D objects from blends of polyethylene and polar polymers.

BACKGROUND

[0003] Traditional manufacturing processes, known as “subtractive manufacturing”, use material that are carved or shaped into a desired product by parts of the material being removed in a variety of ways. Additive manufacturing, also known as 3-D printing, was created to do the opposite. In additive manufacturing, a 3-D object is made by successively adding material layer-by-layer to produce a product having a predetermined geometry. The design of the 3-D object is typically made and controlled by a computer. A computer-aided design (CAD) software program is typically used to relay messages to a 3-D printer so that it “prints” in the desired shape.

[0004] The benefits of this more modem technology are that new products can be made with massive customization, improved material utilization, and a greater range of designs. Designs that cannot be manufactured in one entire piece with traditional means can easily be achieved using additive manufacturing. For example, shapes with a scooped out or hollow center can be produced as a single piece, without the need to weld or attach individual components together. Due to such benefits, additive manufacturing has found application in, for example, the plastics, construction, and automotive industries.

[0005] Because of its relative simplicity, the additive manufacturing process known as fused filament fabrication (FFF) is widely used for the production of plastics. In FFF, filaments of a thermoplastic are melted or extruded through a hot end of a nozzle and deposited as layers that harden and build up to form the desired 3-D object. Currently, two commercially available thermoplastics (i.e., acrylonitrile-butadiene-styrene (ABS) and polylactic acid (PLA)) and three engineering thermoplastics (i.e., polycarbonate (PC), poly(ether imide) (PEI), and polyether ether ketone (PEEK)) are primarily used for FFF due to their availability and ability to form products with adequate mechanical properties and dimensional accuracy. One drawback for using such specialty polymers is their high cost.

[0006] Ideally, low cost commodity thermoplastics could be used in additive manufacturing via FFF. However, there are challenges that arise from the nature of the FFF process with using commodity thermoplastics, particularly polyolefins. For example, degradation of mechanical properties of the final product can occur as a result of internal interfaces between the layers of deposited polymer. Also, the final product can experience warpage due to crystallization induced stresses caused by thermal expansion.

[0007] A need therefore exists for a thermoplastic that is suitable for use in additive manufacturing, particularly FFF, and can be used to produce products having adequate mechanical properties and less warpage.

[0008] Additional references of interest may include: CN103980395B, CN103980396 A, JP2018/035461A, JP2019/203228A, and WO2019/197582A1.

SUMMARY OF INVENTION

[0009] A process for making an obj ect using an additive manufacturing process is provided herein. In some examples, a blend can be prepared that can include polyethylene and a polar polymer. The blend can be extruded to make a filament. The filament can be inserted into an additive manufacturing apparatus that can have a nozzle. The filament can be heated. A fluid bead of the filament can be dispensed out of the nozzle to manufacture a three-dimensional object.

[0010] A process for making a filament is also provided herein. In some examples, a blend can be prepared that can include polyethylene and a polar polymer. The blend can be extruded to make a filament where the filament has a diameter from 0.01 mm to 1 m. The filament can be collected on a spool.

[0011] A filament is also provided herein. The filament can include a blend of polyethylene and a polar polymer. The filament can have a diameter from about 1 mm to about 3 mm.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0012] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, and/or functions of the invention.

Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the Figures. Moreover, the exemplary embodiments presented below can be combined in any combination of ways, i.e., any element from one exemplary embodiment can be used in any other exemplary embodiment, without departing from the scope of the disclosure.

[0013] For purposes of this invention and the claims thereto, a “catalyst system” is a combination of at least one catalyst compound, an activator, and a support material. The catalyst systems may further comprise one or more additional catalyst compounds. The terms “mixed catalyst system”, “dual catalyst system”, “mixed catalyst” are used to indicate two or more catalyst compounds in the catalyst system. The term “supported catalyst system” may be used interchangeably herein with “catalyst system.” For the purposes of this invention and the claims thereto, when catalyst systems are described as comprising neutral stable forms of the components, it is well understood by one of ordinary skill in the art, that the ionic form of the component is the form that reacts with the monomers to produce polymers.

[0014] The term “complex” is used to describe molecules in which an ancillary ligand is coordinated to a central transition metal atom. The ligand is bulky and stably bonded to the transition metal so as to maintain its influence during use of the catalyst, such as polymerization. The ligand may be coordinated to the transition metal by covalent bond and/or electron donation coordination or intermediate bonds. The transition metal complexes are generally subjected to activation to perform their polymerization function using an activator which is believed to create a cation as a result of the removal of an anionic group, often referred to as a leaving group, from the transition metal. "Complex," as used herein, is also often referred to as "catalyst precursor", "pre-catalyst", "catalyst", "catalyst compound", "metal compound", "transition metal compound", or "transition metal complex". These words are used interchangeably. “Activator” and “cocatalyst” are also used interchangeably.

[0015] The terms "hydrocarbyl radical," "hydrocarbyl" and "hydrocarbyl group" are used interchangeably throughout this document. Likewise the terms "group", "radical", and "substituent" are also used interchangeably in this document. For purposes of this invention, "hydrocarbyl radical" is defined to be C₁-C₁₀₀ radicals, that may be linear, branched, or cyclic, and when cyclic, aromatic or non-aromatic.

[0016] For purposes of this invention and claims thereto, unless otherwise indicated (e.g., the definition of "substituted hydrocarbyl" etc.), the term “substituted” means that a hydrogen group has been replaced with at least one non-hydrogen group, such as a hydrocarbyl group, a heteroatom, or a heteroatom containing group. For example, substituted hydrocarbyl radicals can be radicals in which at least one hydrogen atom of the hydrocarbyl radical has been substituted with at least one functional group , such as halogen (such as Br, Cl, F or I) or at least one functional group such as -NR*₂, -OR*, -SeR*, -TeR*, -PR*₂, -AsR*₂, -SbR*₂, -SR*, -BR*₂, -SiR*₃, -GeR*₃, -SnR*₃, -PbR*₃, -(CH₂)q-SiR*₃, and the like, where q is 1 to 10 and each R* is independently hydrogen, a hydrocarbyl or halocarbyl radical, and two or more R* may join together to form a substituted or unsubstituted completely saturated, partially unsaturated, or aromatic cyclic or polycyclic ring structure), or where at least one heteroatom has been inserted within a hydrocarbyl ring.

[0017] The term "substituted hydrocarbyl" means a hydrocarbyl radical in which at least one hydrogen atom of the hydrocarbyl radical has been substituted with at least one heteroatom (such as halogen, e.g., Br, Cl, F or I) or heteroatom-containing group (such as a functional group, e g., -NR*₂, -OR*, -SeR*, -TeR*, -PR*₂, -AsR*₂, -SbR*₂, -SR*, -BR*₂, -SiR*₃, -GeR*₃, -SnR*₃, -PbR*₃, -(CH₂)q-SiR*₃, and the like, where q is 1 to 10 and each R* is independently hydrogen, a hydrocarbyl or halocarbyl radical, and two or more R* may join together to form a substituted or unsubstituted completely saturated, partially unsaturated, or aromatic cyclic or polycyclic ring structure), or where at least one heteroatom has been inserted within a hydrocarbyl ring.

[0018] The term "ring atom" means an atom that is part of a cyclic ring structure. By this definition, a benzyl group has six ring atoms and tetrahydrofuran has 5 ring atoms.

[0019] A "ring carbon atom" is a carbon atom that is part of a cyclic ring structure. By this definition, a benzyl group has six ring carbon atoms and para-methylstyrene also has six ring carbon atoms.

[0020] The term "aryl" or "aryl group" means a six carbon aromatic ring, including but not limited to, phenyl, 2-methyl-phenyl, xylyl, 4-bromo-xylyl. Likewise, heteroaryl means an aryl group where a ring carbon atom (or two or three ring carbon atoms) has been replaced with a heteroatom, preferably, N, O, or S. A substituted aryl group is an aryl group having 1 or more hydrogen groups replaced by a hydrocarbyl, substituted hydrocarbyl, heteroatom or heteroatom containing group.

[0021] A "heterocyclic ring" is a ring having a heteroatom in the ring structure as opposed to a heteroatom substituted ring where a hydrogen on a ring atom is replaced with a heteroatom. For example, tetrahydrofuran is a heterocyclic ring and 4-N,N-dimethylamino-phenyl is a heteroatom substituted ring.

[0022] As used herein the term "aromatic" also refers to pseudoaromatic heterocycles which are heterocyclic substituents that have similar properties and structures (nearly planar) to aromatic heterocyclic ligands, but are not by definition aromatic. The term "substituted aromatic," means an aromatic group having 1 or more hydrogen groups replaced by a hydrocarbyl, substituted hydrocarbyl, heteroatom or heteroatom containing group.

[0023] The term "continuous" means a system that operates without interruption or cessation. For example, a continuous process to produce a polymer would be one where the reactants are continually introduced into one or more reactors and polymer product is continually withdrawn.

[0024] As used herein, the numbering scheme for the Periodic Table groups is the new notation as set out in Chemical and Engineering News, v.63(5), pg. 27, (1985).

[0025] An "olefin", is a linear, branched, or cyclic compound of carbon and hydrogen having at least one double bond. For purposes of this specification and the claims appended thereto, when a polymer or copolymer is referred to as comprising an olefin, the olefin present in such polymer or copolymer is the polymerized form of the olefin. For example, when a copolymer is said to have an "ethylene" content of 35 wt% to 55 wt%, it is understood that the mer unit in the copolymer is derived from ethylene in the polymerization reaction and said derived units are present at 35 wt% to 55 wt%, based upon the weight of the copolymer. A “polymer” has two or more of the same or different mer units. A “homopolymer” is a polymer having mer units that are the same. A “copolymer” is a polymer having two or more mer units that are different from each other. “Different” as used to refer to mer units indicates that the mer units differ from each other by at least one atom or are different isomerically. Accordingly, the definition of copolymer, as used herein, includes terpolymers and the like. An "ethylene polymer" or "ethylene copolymer" is a polymer or copolymer comprising at least 50 mol% ethylene derived units, a "propylene polymer" or "propylene copolymer" is a polymer or copolymer comprising at least 50 mol% propylene derived units, and so on.

[0026] A “random copolymer” is a polymer having individual repeating units of one of the monomers present in a random or statistical distribution in the polymer chain. A “propylene random copolymer” is a propylene polymer having repeating units of the ethylene monomer(s) present in a random or statistical distribution in the polymer chain.

[0027] As used herein, M_n is number average molecular weight, M_w is weight average molecular weight, and M_z is z average molecular weight, wt% is weight percent, and mol% is mole percent. Molecular weight distribution (MWD), also referred to as polydispersity index (PDI), is defined to be M_w divided by M_n. Unless otherwise noted, all molecular weights (e.g., M_w, M_n, M_z) are reported in units of g/mol. The following abbreviations may be used herein: Me is methyl, Et is ethyl, t-Bu and ^lBu are tertiary butyl, iPr and ¹ Pr are isopropyl, Cy is cyclohexyl, THF (also referred to as thf) is tetrahydrofuran, Bn is benzyl, Ph is phenyl, Cp is cyclopentadienyl, Cp* is pentamethyl cyclopentadienyl, Ind is indenyl, Flu is fluorenyl, and MAO is methylalumoxane.

[0028] As used herein, the term "polypropylene", "propylene polymer," or "PP" refers to homopolymers, copolymers, terpolymers, and interpolymers, typically comprising from 50 to 100 mol% propylene. Alternately the polypropylene comprises 50 to 100 weight % of propylene.

[0029] As used herein "semi-crystalline polymer" is defined to be an olefin polymer having a melting point (Tm) of 100°C or more (as measured by DSC-second melt, described below). As used herein a "semi-amorphous polymer" is defined to be an olefin polymer having a heat of fusion of between 4 and 70 J/g (as determined by DSC, described in test methods below). Melting point (Tm), peak crystallization temperature (Tc), heat of fusion (Hf) and percent crystallinity are determined using differential scanning calorimetric (DSC) procedure in the test methods below.

[0030] As used herein, the term “polar polymer” means a polymer having a dipole moment that is greater than 0 D at 25 °C.

[0031] This invention relates to a novel 3D printing material which can include a blend of a polyethylene and a polar polymer.

[0032] It has been surprising and unexpectedly discovered that using an additive manufacturing process such as fused filament fabrication to make 3-D objects from blends of polyethylene and a polar polymer can have reduced shrinkage, reduced warpage, and are capable of forming a uniform diameter printing filament.

[0033] Typically, the polyethylene(s) are present in the compositions of the present invention at from 40 wt% to 99.9 wt% (based upon the weight of the polyethylene and the semi-amorphous polymer) in one embodiment, and from 50 wt% to 99 wt% in another embodiment, and from 60 wt% to 98 wt% in yet another embodiment, and from 70 wt% to 99 wt% in yet another embodiment, and from 80 wt% to 97 wt% in yet another embodiment, and from 90 wt% to 98 wt% in yet another embodiment, wherein a desirable range may be any combination of any upper wt% limit with any lower wt% limit described herein. [0034] In another embodiment, the polar polymer is present at 60 wt% to 0.01 wt% (based upon the weight of the polyethylene and the polar polymer), in one embodiment 50 wt% to 1 wt%, in another embodiment 40 wt% to 1 wt%, in yet another embodiment 30 wt% to 1 wt%, alternately 20 wt% to 3 wt%, in yet another embodiment 15 wt% to 1 wt%, in yet another embodiment 10 wt% to 4 wt%; in yet another embodiment, wherein a desirable range may be any combination of any upper wt% limit with any lower wt% limit described herein.

[0035] In a preferred embodiment, the Mw of the polyethylene is different from the Mw of the polar polymer. The blend used in the additive manufacturing process can have a bimodal molecular weight distribution. In one embodiment, the Mw of the polyethylene can be lower than the Mw of the polar polymer. Alternatively, the Mw of the polyethylene can be higher than the Mw of the polar polymer. A blend with bimodal molecular weight distribution can enhance shear thinning and thus improve the printing process and other characteristics. In one embodiment, the MWD of the blend can be 4 or more, preferably 5 or more, more preferably 10 or more.

Polar Polymer

[0036] In some examples, the polar polymer can comprise 50.0 wt% to 99.0 wt%, 55 0 wt% to 95.0 wt%; 60.0 wt% to 90.0 wt%; or 65.0 wt% to 95.0 wt% ethylene based on the weight of the polar poly mer. In some examples, the polar polymer can comprise at least 50.0 wt%, at least 55.0 wt%, at least 60.0 wt%, or at least 65.0 wt% ethylene based on the weight of the polar polymer. In some examples, the polar polymer can have a dipole moment at 25°C of at least 0, at least 0.25 D, at least 0.50 D, at least 0.75 D, at least 1 D, at least 1.5 D, or at least 2 D. In some examples, the polar polymer can have a dipole moment at 25°C from 0.1 D to 3 D, from 0.1 D to 2 D, from 0.1 D to 1.5 D, from 0,25 D to 3 D, from 0.25 D to 2 D, from 0.25 D to 1.5 D, from 0.5 D to 3 D, from 0.5 D to 2 D, or from 0.5 D to 1.5 D.

[0037] In some examples, the polar polymer can comprise a polymer unit derived from one or more polar comonomers. The amount of polymer units derived from polar comonomers can be up to 95.0 wt% and can also range from about 1.0 wt% to about 50 wt%; about 1.0 wt% to about 49.0 wt%; about 5.0 wt% to about 45.0 wt%; about 10.0 wt% to about 50.0 wt%; about 10.0 wt% to about 40.0 wt%; or about 30.0 wt% to about 45.0 wt%, based on the total weight of the polar polymer. The amount of polymer units derived from polar comonomers can also range from a low of about 1.0 wt%, 4.0 wt%, or 7.0 wt% to a high of about 30.0 wt%, 40.0 wt%, 45.0 wt%, or 50 wt% based on the total weight of the polar polymer. Suitable polar comonomers include, but are not limited to: vinyl ethers such as vinyl methyl ether, vinyl n-butyl ether, vinyl phenyl ether, vinyl beta-hydroxy-ethyl ether, and vinyl dimethylamino- ethyl ether; olefins such as propylene, butene-1, cis-butene-2, trans-butene-2, isobutylene, 3,3-dimethylbutene-1,4-methylpentene-1, octene-1, and styrene; vinyl type esters such as vinyl acetate, vinyl butyrate, vinyl pivalate, and vinylene carbonate; haloolefms such as vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, vinyl chloride, vinylidene chloride, tetrachloroethylene, and chlorotrifluoroethylene; acrylic-type esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, alpha-cyanoisopropyl acrylate, beta-cyanoethyl acrylate, o-(3-phenylpropan-l,3-dionyl)phenyl acrylate, methyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, methyl methacrylate, glycidyl methacrylate, beta-hydroxethyl methacrylate, beta-hydroxpropyl methacrylate, 3-hydroxy-4-carbo-methoxy-phenyl methacrylate, N,N-dimethylaminoethyl methacrylate, t-butylaminoethyl methacrylate, 2-(l-aziridinyl)ethyl methacrylate, diethyl fumarate, diethyl maleate, and methyl crotonate; other acrylic-type derivatives such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, methyl hydroxy, maleate, itaconic acid, acrylonitrile, fumaronitrile, N,N-dimethylacrylamide, N-isopropylacrylamide, N-t-butylacrylamide, N-phenylacrylamide, diacetone acrylamide, methacrylamide, N-phenylmethacrylamide, N-ethylmaleimide, and maleic anhydride; and other compounds such as allyl alcohol, vinyltrimethylsilane, vinyltriethoxysilane, N-vinylcarbazole, N-vinyl-N-methylacetamide, vinyldibutylphosphine oxide, vinyldiphenylphosphine oxide, bis-(2-chloroethyl) vinylphosphonate and vinyl methyl sulfide. [0038] In some examples, the polar comonomer can be vinyl acetate (VA). In some examples, the polar polymer can be an ethylene vinyl acetate copolymer (EVA). The EVA can have about 5.0 wt% to about 95.0 wt%, or about 20.0 wt% to about 80.0 wt%, polymer units derived from vinyl acetate, based on the weight of the polymer units derived from ethylene and vinyl acetate. The amount of polymer units derived from vinyl acetate can range from a low of about 20.0 wt%, 25.0 wt%, 30.0 wt%, 35.0 wt%, or 40.0 wt% to a high of about 45.0 wt%, 50.0 wt%, 55.0 wt%, 60.0 wt%, or 80.0 wt%, based on the total weight of the polar polymer. In certain embodiments, the EVA can further include polymer units derived from one or more comonomer units selected from propylene, butene, 1 -hexene, 1-octene, and/or one or more dienes. Suitable dienes include, for example, 1,4-hexadiene, 1,6-octadiene, 5-methyl-1,4- hexadiene, 3, 7-dimethyl- 1,6-octadiene, dicyclopentadiene (DCPD), ethylidene norbomene (ENB), norbomadiene, 5-vinyl-2-norbomene (VNB), and combinations thereof.

[0039] In some examples, the polar polymer can he polyethylene grafted with maleic anhydride or an EP elastomers grafted with maleic anhydride. The polyethylene that the maleic anhydride is grafted onto can include one or more of the following properties: 1. a Mw of 30,000 to 2,000,000 g/mol preferably 50,000 to 1,000,000 g/mol, more preferably 90,000 to 500,000 g/mol, as measured by GPC as described below in the test methods; and/or

2. a M_w/M_n of 1 to 40, preferably 1.6 to 20, more preferably 1.8 to 10, more preferably 1.8 to 3 as measured by GPC as described below in the test methods; and/or

3. a Tm (second melt) of 30 to 200°C, preferably 30 to 185°C, preferably 50 to 175°C, more preferably 60 to 170°C, more preferably 70 to 165°C, more preferably 75 to 160°C, more preferably 100 to 165°C, more preferably 115 to 165°C as measured by the DSC method described below in the test methods; and/or

4. a crystallinity of 5 to 80%, preferably 10 to 70, more preferably 20 to 60%, more preferably 10 to 95%, more preferably 50 to 95%, more preferably 60 to 95%, more preferably 60 to 80%, more preferably 50 to 80% as measured by the DSC method described below in the test methods; and/or

5. a glass transition temperature (Tg) of -40°C to 20°C, preferably -20°C to 10°C, more preferably -10°C to 5°C as measured by the DMA method described below; and/or

6. a heat of fusion (Hf) of 180 J/g or less, preferably 20 to 150 J/g, more preferably 40 to 120 J/g as measured by the DSC method described below in the test methods; and/or

7. a crystallization temperature (Tc) of 15 to 120°C, preferably 20 to 115°C, more preferably 25 to 110°C, preferably 60 to 145°C, as measured by the DSC method described below in the test methods; and/or

8. a heat deflection temperature of 45 to 140°C, preferably 60 to 135°C, more preferably 75 to 125°C (as measured according to ASTM D648-18, using a load of 0.45 MPa); and/or

9. a g'(vis) of 0.90. (preferably at least 0.93, preferably at least 0.95. preferably at least 0.96, preferably at least 0.98) as measured by DSC; and/or

10. A density from a lower limit of 0.940 or 0.945 or 0.950 or 0.955 or 0.960 g/cm³ to an upper limit of 0.975 or 0.972 or 0.970 or 0.968 g/cm³.

[0040] In some examples, the EP elastomers can be EPM copolymers or EPDM terpolymers having the foil owing formulas:

[0041] The values of m and n are selected to satisfy (a) the mole ratios of the ethylene and propylene in the copolymer and (b) the molecular weight of the copolymers, both of which are described below.

where R is selected from 5 ethyldiene - 2 - norbomine; 1 - 4 - hexadiene; 5 - phenyl - 2- norbomene, and dicyclopentadiene. The values of x,y, and z are selected to satisfy (a) the mole ratios of the comonomers and (b) the molecular weight, both of which are described below.

[0042] The ethylene content of the EPM copolymer can be from 20 mol% to 90 mol%, preferably from 30 mol% to 80 mol%, and most preferably 40 mol% to 60 mol%, with a Mooney viscosity of from 7 to 90 (ML (1+4) at 125°C) and 0 gel. The number average molecular weight of the EP elastomer can be from 40.000 g/mol to 150,000 g/mol, preferably 40,000 g/mol to 100,000 g/mol, most preferably 50,000 g/mol to 80,000 g/mol. The copolymer may be amorphous or crystalline.

[0043] The preparation of the EPM copolymers are well known in the art, as disclosed in US Patent 4,670,515, the disclosure of which is incorporated herein by reference.

[0044] The EPDM elastomers are terpolymers containing from 20 to 90 mole percent (preferably 40 to 90 mole %) of ethylene, from 20 to 70 mole percent of propylene, and from 1 to 20 mole percent of the diene monomer. The dienes include 5 - ethylidene - 2 - norbomene; 1, 4 - hexadiene, 5 - phenyl - 2 - norbomene, and dicyclopentadiene. As stated in the Encyclopedia of Polymer Science and Engineering, v.6, pp. 522-523, ethylene-propylene elastomers are made from the basic building blocks of ethylene and propylene and may be combined with a third, or even a fourth, monomer to provide the olefinic sites along the backbone. The term "EPDM elastomers" include terpolymers and tetrapolymers that include at least monomers of ethylene, propylene, and diene.

[0045] The preferred EPDM elastomers (ethylene/propylene/5 - ethylidene - 2 - norbomene) have about 0.5 to about 12 wi% 5 - ethylidene - 2 - norbomene monomer, about 30 to 70 wt% ethylene, with the balance of the polymer being propylene. A typical ethylene/propylene/5 - ethylidene - 2 - norbomene teipolymer has an ethylene content of about 50 wt% and a 5 - ethylidene - 2 - norbomene content of about 5 wt%. The terpolymers useful in the present invention have a number average molecular weight (M_n), as measured by GPC, of about 40,000 to about 150,000, more preferably of about 40,000 to about 100,000, and most preferably of about 50,000 to about 80,000, Ail polymer molecular weights quoted herein are number average molecular weights unless otherwise indicated. The Mooney viscosity (ML 1+4, 125 °C) of the terpolymer is about 7 to about 90. more preferably of about 10 to about 80 and most preferably about 20 to about 70. The EPDM should have a low crystallinity (<50%) and preferably less than 30%. The degree of crystallinity and molecular weight ranges are particularly important. Generally, low to zero crystallinity is preferred because of better solubility and better dispersahility, as is low molecular weight EPDM. EPDM terpolymers useful in the present invention are commercially available in a variety of grades from a number of manufacturers, including Exxon Chemical Co., Uniroyai, Dupont, DSM Copolymer, and Polysar to name a few.

[0046] Maleic Anhydride and other Dicarboxylic Acid Anhydrides: In some examples, the polyethylene or the EP elastomer can he grafted with a dicarboxylic acid anhydride having the following formula:

in which R is an alkyl group having from 0-4 carbon atoms and Y is preferably hydrogen but may be an organic group such as a branched or straight chain alkyl group of 1-12 carbon atoms. [0047] Grafting Process: The maleic anhydride (or other dicarboxylic acid anhydride) can be grafted onto the polyethylene or the ethylene-propylene elastomer within the range of 0.01 wt% to 5 wt%, preferably within 0.1 wt% to 5 wt%, preferably within 0.05 wt% to 4 wt% and most preferably 0.1 wt% to 1.5 wt% based on the weight of the polar polymer.

[0048] Methods of grafting maleic anhydride onto the backbone of polyethylene, copolymers and terpolymers is well known in the art. The grafting process may be carried as described in the above referenced US Patent No. 4,670,515.

[0049] Another grafting method is a free radical process described in US Patent 4,661,554. This process employs a free radical generator (organic peroxides such as dicumylperoxide or benzothiazyl disulfide, the later being preferred). The polyethylene or EP elastomer, maleic anhydride (or other anhydride) and free radical generator can be charged to a mixer such as a twin extruder and subjected to elevated temperatures (typically 100°C - 200°C). The reaction may produce some cross linking which, for purposes of the present invention, can be tolerated. Generally an amount of the maleic anhydride (or other anhydride) in excess of that to be grafted onto the polymer backbone can he used to ensure sufficient grafting. [0050] Maleated polyethylene is available as Exxelor PE 1040 from ExxonMobil Chemical Company. Maleated EPM copolymer is available as Exxelor 1801 and 1803 from ExxonMobil Chemical Company, Maleated EPDM terpolymer is available as Royaltuf 465 and 490 from Uniroyal.

Polyethylene

[0051] In some examples, the polyethylene can be an ethylene homopolymer or ethylene copolymer. The ethylene copolymer can have less than 5 wt%, less than 3 wt%, less than 1 wt% or less than 0.1 wt% of a comonomer based on the weight of the ethylene copolymer. Suitable comonomers can include C₃-C₂₀ alpha-olefins, preferably C₃-C₈ C₅-C₂₀ cyclic olefins, preferably C₇-C₁₂ cyclic olefins, C₇-C₂₀ vinyl aromatic monomers, preferably styrene, and C₄-C₂₀ disubstituted olefins, preferably isobutylene. The most preferred comonomers can include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene. The polyethylene can have a density from a lower limit of 0.940 or 0.945 or 0.950 or 0.955 or 0.960 g/cm³ to an upper limit of 0.975 or 0.972 or 0.970 or 0.968 g/cm³, with ranges from any lower limit to any upper limit being contemplated. The melt index of the polyethylene, as measured according to ASTM D1238-13, condition 190°C, 2.16 kg, can be from a lower limit of 0.1 or 1 or 5 or 10 or 30 or 50 to an upper limit of 500 or 300 or 200 or 100 or 50 or 40 or 30 or 20 or 10 g/10 min, with ranges from any lower limit to any upper limit being contemplated. The melt index of the polyethylene, as measured according to ASTM D1238-13, condition 190°C, 2.16 kg, can be from 0.1 g/10 min to 30 g/10 min, alternatively from 0.1 g/10 min to 6 g/10 min, or alternatively, less than 1 g/10 min, or less than 0.6 g/10 min. The polyethylene can be any conventional polyethylene having the properties described herein, and can have a broad or narrow molecular weight distribution. In a particular embodiment, the polyethylene can have a value of Mw/Mn of from a lower limit of 1.4 or 1.6 or 1.8 or 2.0 to an upper limit of 15, 10, 5, 4.0 or 3.8 or 3.5 or 3.0, with ranges from any lower limit to any upper limit being contemplated.

[0052] Industrial methods of producing the polyethylene components of the invention are well known in the art as is exemplified in the references cited above. Any such method capable of producing polyethylene polymer components according to the invention can be suitable. Such methods can include gas phase, liquid phase (or solution), and slurry phase polymerization processes, either alone or in combination (by alone, reference is made to series or serial production in a single reactor or in more than one reactor). Reactor blends can also be suitable, such as by the use of mixed catalysts or mixed polymerization conditions in a single reactor. Illustrative examples may be found in US Pat. Nos. 4,543,399, 4,588,790, 5,028,670, 5,352,749, 5,382,638, 5,405,922, 5,422,999, 5,436,304, 5,453,471, 5,462,999 and 5,463,999, and International applications WO 1994/028032, WO 1995/007942 and WO 1996/000245.

These processes can use either traditional Ziegler-Natta catalysts or later organometallic catalysts characterized as having essentially single polymerization sites due to the arrangement of ancillary ligands on or about the metal center. Metallocene catalysts are representative “single site catalysts” and are preferred in this invention in embodiments having narrow molecular weight distribution polyolefins. Typically, the processes are conducted at temperatures of from about -100°C to 150°C, more typically from about 40°C to 120°C, at pressures up to about 7,000 kPa, typically from about 690 kPa to 2415 kPa. Continuous processes using fluidized beds and recycle streams as the fluidizing medium are preferred. [0053] Slurry polymerization processes are suitable for both components and particularly suited for the high-density components. These processes are typically described as those in which the polymerization medium can be either a liquid monomer, like ethylene, or a hydrocarbon solvent or diluent, advantageously aliphatic paraffin such as propane, isobutane, hexane, heptane, cyclohexane, etc. or an aromatic one such as toluene. Slurry solids typically include the forming polymer and inert carrier-supported catalysts. Catalysts are typically Ziegler-Natta, and/or one or more single site catalysts, such as metallocenes. The polymerization temperatures may be those considered low, e.g., less than 50°C, typically 0°C-30°C, or may be in a higher range, such as up to about 150°C, typically from 50°C up to about 80°C, or at any ranges between the end points indicated. Pressures can vary from about 100 to about 700 psia (0.76-4.8 MPa). Additional description is given in US Pat. Nos. 4,182,810, 5,274,056, 6,319,997, 6,380,325, 6,420,497, WO 1994/021962 and

WO 1999/032531.

[0054] Preferred polyethylenes useful in this invention can have one or more of the following:

1. a Mw of 30,000 to 2,000,000 g/mol preferably 50,000 to 1,000,000 g/mol, more preferably 90,000 to 500,000 g/mol, as measured by GPC as described below in the test methods; and/or

2. a Mw/Mn of 1 to 40, preferably 1.6 to 20, more preferably 1.8 to 10, more preferably 1.8 to 3 as measured by GPC as described below in the test methods; and/or

3. a Tm (second melt) of 30 to 200°C, preferably 30 to 185°C, preferably 50 to 175°C, more preferably 60 to 170°C, more preferably 70 to 165°C, more preferably 75 to 160°C, more preferably 100 to 165°C, more preferably 115 to 165°C as measured by the DSC method described below in the test methods; and/or 4. a crystallinity of 5 to 80%, preferably 10 to 70, more preferably 20 to 60%, more preferably 10 to 95%, more preferably 50 to 95%, more preferably 60 to 95%, more preferably 60 to 80%, more preferably 50 to 80% as measured by the DSC method described below in the test methods; and/or

9. a g'(vis) of 0.90, (preferably at least 0.93, preferably at least 0.95, preferably at least 0.96, preferably at least 0.98) as measured by DSC.

[0055] In one embodiment, the polyethylene can have a molecular weight distribution (Mw/Mn) of up to 40, preferably ranging from 1.5 to 10, and from 1.8 to 7 in another embodiment, and from 1.9 to 5 in yet another embodiment, and from 2.0 to 4 in yet another embodiment. In another embodiment the polyethylene can have a Gardner impact strength, tested on 0.125 inch disk at 23°C, that may range from 20 in-lb to 1,000 in-lb in one embodiment, and from 30 in-lb to 500 in-lb in another embodiment, and from 40 in-lb to 400 in-lb in yet another embodiment (as determined by ASTM D 5420-16). In yet another embodiment, the 1% secant flexural modulus (as determined by ASTM D 790-17 (A, 1.3 mm/min)) may range from 100 MPa to 2,300 MPa, and from 200 MPa to 2,100 MPa in another embodiment, and from 300 MPa to 2,000 MPa in yet another embodiment, wherein a desirable polyethylene may exhibit any combination of any upper flexural modulus limit with any lower flexural modulus limit. The melt flow rate (MFR) (ASTM D 1238-13, 230°C, 2.16 kg) of preferred polyethylene range from 0.1 dg/min to 2,500 dg/min in one embodiment, from 0.3 to 500 dg/min in another embodiment, from 0.1 dg/min to 3 dg/min, from 10.0 dg/min to about 4,000.0 dg/min, from 20.0 dg/min to about 4,000.0 dg/min, from about 50.0 dg/min to about 3,000.0 dg/min, from about 100.0 to about 2,000.0, or from about 400.0 dg/min to about 2,000.0 dg/min.

[0056] The polyethylene can be unimodal or multimodal with respect to one or more of molecular weight distribution, comonomer distribution or density distribution. A multimodal polyolefin may have at least two polymer components which have different weight average molecular weight, preferably a lower weight average molecular weight (LMW) and a higher weight average molecular weight (HMW). A unimodal polyolefin is typically prepared using a single stage polymerization, e.g. solution, slurry or gas phase polymerization, in a manner well- known in the art. A multimodal (e.g. bimodal) polyethylene can be produced by mechanically blending two or more, separately prepared polymer components or by in-situ blending in a multistage polymerization process during the preparation process of the polymer components. Both mechanical and in-situ blending are well-known in the field. A multistage polymerization process may preferably be carried out in a series of reactors, such as a loop reactor which may be a slurry reactor and/or one or more gas phase reactor(s). Preferably a loop reactor and at least one gas phase reactor is used. The polymerization can also be preceded by a pre-polymerization step.

[0057] Preferred polyethylene can be used in the practice of this invention include those sold by ExxonMobil Chemical Company in Houston Texas, including those sold as ExxonMobil HDPE.

[0058] In some embodiments, polyethylene can be produced with a Ziegler-Natta catalyst that preferably includes a solid titanium catalyst component comprising titanium as well as magnesium, halogen, at least one non-aromatic “internal” electron donor, and at least one, preferably two or more “external” electron donors. The solid titanium catalyst component, also referred to as a Ziegler-Natta catalyst, can be prepared by contacting a magnesium compound, a titanium compound, and at least the internal electron donor. Examples of the titanium compound used in the preparation of the solid titanium catalyst component include tetravalent titanium compounds having the formula Ti(ORn)X4-n, wherein “R” is a hydrocarbyl radical, “X” is a halogen atom, and n is from 0 to 4. For purposes of this disclosure, a hydrocarbyl radical is defined to be C₁ to C₂₀ radicals, or C₁ to C₁₀ radicals, or C₆ to C₂₀ radicals, or C₇ to C₂₁ radicals that may be linear, branched, or cyclic where appropriate (aromatic or non- aromatic).

[0059] In some embodiments, polyethylene can be produced with a metallocene catalyst.

A "metallocene" catalyst compound is a transition metal catalyst compound having one, two or three, typically one or two, substituted or unsubstituted cyclopentadienyl ligands bound to the transition metal, typically a metallocene catalyst is an organometallic compound containing at least one π-bound cyclopentadienyl moiety (or substituted cyclopentadienyl moiety).

Substituted or unsubstituted cyclopentadienyl ligands include substituted or unsubstituted indenyl, fluorenyl, tetrahydro-s-indacenyl. tetrahydro-as-indacenyl. benz[f]indenyl, benz[e]indenyl. tetrahydrocyclopenta[b]naphthalene, tetrahydrocyclopenta[a]naphthalene, and the like.

Additives

[0060] Additives may be included in the polyethylene, the polar polymer, or the blends of the polyethylene and the polar polymer. Such additives and their use are generally well known in the art. These include those commonly employed with plastics such as heat stabilizers or antioxidants, plasticizers, neutralizers, slip agents, antiblock agents, pigments, metal deactivators, stearates, antifogging agents, antistatic agents, clarifiers, nucleating agents, ultraviolet absorbers or light stabilizers, fillers and other additives in conventional amounts. Effective levels are known in the art and depend on the details of the base polymers, the fabrication mode and the end application. In some examples, fillers are present in the blend in an amount of up 50 wt%, up to 40 wt%, up to 30 wt%, up to 20 wt% based on a combined weight of the additives, the polyethylene, and the semi-amorphous polymer. In some examples, fillers are present in the blend in an amount from about 1 wt% to about up 50 wt%, from about 5 wt% to about up 50 wt%, from about 10 wt% to about up 50 wt%, from about 20 wt% to about up 50 wt%, from about 1 wt% to about up 40 wt%, from about 5 wt% to about up 40 wt%, from about 10 wt% to about up 40 wt%, or from about 20 wt% to about up 40 wt% based on a combined weight of the additives, the polyethylene, and the semi-amorphous polymer. In some examples, the filler can be calcium carbonate, magnesium carbonate, carbon black, silica, carbon-silica dual-phase filler, clay (layered silicates), lignin, carbon-nano-tubes, amorphous fillers, such as glass particle based fillers, starch based fillers, or combinations thereof. Foaming Agents

[0061] Foaming agents may generally be divided into two classes: physical foaming agents and chemical foaming agents, both of which may be added to the polyethylene, the polar polymer, or the blends of the polyethylene and the polar polymer.

[0062] Physical foaming or blowing agents are generally gases such as carbon dioxide or nitrogen. Hydrocarbon gases, such as butane or pentane and fluorocarbon gases, such as trichlorofluromethane and dichlorodifluromethane can be effective as physical blowing agents producing good quality foams. Because hydrocarbon and flurocarbon gases are viewed as presenting certain health and environmental concerns, the use of these gases is generally not the most desirable. More desirable physical blowing agents are carbon dioxide, nitrogen and argon. Physical blowing agents are utilized when low foam densities (≤0.5 g/cm³) are required.

[0063] Chemical blowing agents allow the production of foamed produces having a density of generally greater than 0.5 g/cm³. Examples of chemical blowing agents include bicarbonate of soda (used typically in combination with citric acid), azodicarbonamide, sulfonyl hydrazide, sulfonyl semicarbazide. Bicarbonate of soda (endothermic agent) and azodicarbonamide (exothermic agent) are perhaps the most widely used chemical blowing agents.

[0064] When used at low levels, generally less than 1 wt%, and desirably around 0.25 wt% based on the weight of the polymer being foamed, chemical blowing agents may function as bubble nucleating agents and facilitate the formation of more uniformly sized bubble. This function is often utilized even when the primary foaming medium is a physical blowing agent, such as carbon dioxide gas. Talc can also be utilized for bubble nucleation.

Blends

[0065] In one or more embodiments, the blends described herein comprise polyethylene, the polar polymer, optionally additives, and optionally foaming agents and can be formed using any suitable means and are typically blended to yield an intimately mixed composition or a uniform mixture. The blends described herein can be formed using conventional equipment and methods, such as by dry blend using a tumbler, double-cone blender, ribbon blender, or other suitable blender and subsequently subjected to melt mixing in a mixer, or by mixing the components together directly in a mixer, such as, for example, a Banbury mixer, a Haake mixer, a Brabender internal mixer, or a single or twin-screw extruder, which may include a compounding extruder and a side-arm extruder. In other embodiments, the polyethylene and polar polymer are blended by a combination of approaches, for example a tumbler followed by an extruder. Additionally, additives and/or foaming agents can be included in the blend, in one or more components of the blend, and/or in a product formed from the blend, such as a filament, as desired.

[0066] In yet more embodiments, the polyethylene and polar polymer can be blended using a “master batch” approach. The mixing step can take place as part of an additive manufacturing process to fabricate 3D articles, such as in the melting chamber on a 3D printing machine. [0067] In a preferred aspect of the invention, the polyethylene and polar polymer along with additives and/or foaming agents (if present) are “melt blended” in an apparatus such as an extruder (single or twin screw) or batch mixer. Preferably, the screw of the melt extruder has multiple sections along the length of the barrel including the feed, the compression, and the metering sections. The raw material can be fed from the hopper directly into the feed section. The polymer is mainly melted in the compression zone. The polymers exist in a molten state when entering the metering section, which has the main function of reducing the pulsating flow to ensure a uniform delivery rate through the die. Preferably the temperatures of all of the barrels can be independent and can be accurately controlled in a range from 30°C to 250°C. The extruder die is used to shape the molten strand as it leaves the extruder into filament. In one preferred embodiment, the temperature can be increased from about 150°C in the feed section to about 210°C in the metering section of the barrel. In this manner, filaments can be formed from the blend that can have a diameter of about 2.40 mm to about 3.00 mm, preferably about 2.65 mm to about 3.00 mm, and more preferably about 2.75 mm to about 3.00 mm. A preferred method of blending is to include the final stage of blending as part of the filament fabrication step, such as in the extruder used to melt and convey the composition to a printing nozzle (or a die).

[0068] In another aspect of the invention, the polymer components can be blended in solution by any suitable means, by using a solvent that dissolves both components to a significant extent. The blending may occur at any temperature or pressure where the polymers remain in solution. Preferred conditions include blending at high temperatures, such as 20°C or more, preferably 30°C or more over the peak melting point of the polyethylene. Such solution blending could be particularly useful in processes where the polymer components are made by solution process and the mixing step is part of the finishing train, rather than added to the dry polymer in another blending step altogether. Such solution blending could also be particularly useful in processes where the polyethylene is made in a bulk or high pressure process where the both the polymers are soluble in the monomer.

[0069] Rheological properties of the blend can play a key role in controlling and improving the coalescence of the deposited beads on the object being printed. The molten viscosity should he hi eh enoueh to provide structural support and low enough to enable extrusion. The blend preferably has a complex viscosity at a frequency of 0.1 rad/sec and a temperature of 190°C within the range of from 1,000 or 3,000 or 5,000 or 8,000, or 10,000 or 15,000 Pa.s to 20,000 or 50,000 or 100,000 or 500,000 or 1,000,000 Pa.s. The blend preferably has a complex viscosity at a frequency of 100 rad/sec and a temperature of 190°C within the range of from 50 or 100 or 200 or 500 Pa.s to 5,000 or 8,000 or 10,000 or 15,000 Pa.s.

[0070] In one embodiment, the blend has significant shear induced viscosity thinning. Shear thinning is characterized by the decrease of the complex viscosity with increasing shear rate. One way to quantify the shear thinning is to use a ratio of complex viscosity at a frequency of 0.1 rad/s to the complex viscosity at a frequency of 100 rad/s. Preferably, the complex viscosity ratio of the blend is 5 or more, more preferably 10 or more, even more preferably 15 or more when the complex viscosity is measured at 190°C using a small amplitude oscillatory shear (SAOS). [0071] In at least one embodiment, the melt strength of the blend may be from about 1 cN to about 540 cN, about 1 cN to about 50 cN, about 1 cN to about 25 cN, about 3 cN to about 15 cN, about 4 cN to about 12 cN, about 5 cN to about 10 cN, or about 5 cN to about 15 cN, when measured at 190°C. In some embodiments, the blend has a melt strength of at least about 5 cN, at least about 10 cN, or at least about 15 cN, and about 30 up to about 20 cN, when measured at 190°C. The melt strength of a blend at a particular temperature may be determined with a Gottfert Rheotens Melt Strength Apparatus. To determine the melt strength, a composition (e.g., of a film) melt strand extruded from the capillary die is gripped between two counter-rotating wheels on the apparatus. The take-up speed is increased at a constant acceleration of about 12 mm/s². The maximum pulling force (in the unit of cN) achieved before the strand breaks or starts to show draw-resonance is determined as the melt strength. The temperature of the rheometer is set at 190°C. The capillary die has a length of about 30 mm and a diameter of about 2 mm. The film melt is extruded from the die at a speed of about 10 mm/s. The distance between the die exit and the wheel contact point should be about 122 mm. [0072] The polymers suitable for use in the present invention can be in any physical form when used for filament fabrication. In one embodiment, reactor granules, defined as the granules of polymer that are isolated from the polymerization reactor prior to any processing procedures, are used to make blends of the invention. The reactor granules typically have an average diameter of from 50 pm to 10 mm in one embodiment, and from 10 pm to 5 mm in another embodiment. In another embodiment, the polymer is in the form of pellets, such as, for example, having an average diameter of from 1 mm to 10 mm that are formed from melt extrusion of the reactor granules.

Sterilization

[0073] In some examples, the polyethylene, the polar polymer, the blends of the polyethylene and the polar polymer, the filament, or the 3D printed article can be sterilized by radiation sterilization. Radiation sterilization can use gamma, X-ray or electron radiation, which can deactivate microorganisms such as bacteria, fungi, viruses and spores. In some examples, the polyethylene, the polar polymer, the blends of the polyethylene and the polar polymer, the filament, or the 3D printed article can be sterilized by ultraviolet (UV) light. Short wavelength UV light can deactivate microorganisms such as bacteria, fungi, viruses and spores. Radiation sterilization or UV sterilization can occur to one or more of the polyethylene, the polar polymer, the blends of the polyethylene and the polar polymer, the filament, or the 3D printed article. Additive Manufacturing Processes and Devices

[0074] In an additive-manufacturing process, a model of the component that is being produced can be defined in any suitable manner. In some examples, the model can be designed with computer aided design software. The model can include 3D numeric coordinates of the entire configuration of the component including both external and internal surfaces. The model can include a number of successive 2D cross-sectional slices that together form the 3D component.

[0075] As such, additive manufacturing systems can be used to print or otherwise build three-dimensional ("3D") parts from digital representations of the 3D parts using one or more additive manufacturing techniques, such as fused filament fabrication.

[0076] At an initial stage, the digital representation of the 3D part is sliced into multiple horizontal layers. For each sliced layer, a path is then generated, which provides instructions for the additive manufacturing system to print the given layer.

[0077] Conventional fused filament fabrication printers designs and methods of operation can be found in US Pat. No. 7,604,470. In some examples, fused filament fabrication printers can be provided with one or more than one printing nozzle.

[0078] The 3D printing filament used in the process can include a blend comprising polyethylene and a polar polymer as described above. The polyethylene, the polar polymer, and optional additives can be blended before being extruded into a filament or they can be blended as they are extruded into a filament. Any suitable processes to make 3D filaments can be used, such as the process described in the examples below.

[0079] A three-dimensional structure can be formed through consecutive deposition of a filament using the extrusion nozzle. Examples of devices suitable for performing additive manufacturing processes include any commercially available device for such purpose. The three-dimensional structure can be built in layers, the depth of each layer typically being controllable by selectively adjusting the output from each extrusion nozzle.

[0080] The devices can utilize a computing system which implements design tools and/or topology optimization according to desired design aspects. The system can include a memory. The memory can store data. The memory can store executable instructions used to implement the topology optimization according to the desired design.

[0081] The specification can be transferred to an additive manufacturing device which performs the additive manufacturing techniques according to the specification in order to create the 3D structure. While not required in all aspects, the additive manufacturing device can include processors that interpret the specification, and control other elements which apply the materials using robots, nozzles, lasers or the like to add the materials as layers or coatings to produce the 3D structure.

[0082] The machine controller can control the operation of the extrusion nozzle along the "X," "Y," and "Z" axes via a plurality of drive motors. Each of these motors can be operating separately, or one or more of them may be operating simultaneously, depending upon the shape of the structure to be formed. Circular patterns for each layer can be generated by controlled movement along the "X" and "Y" axes of the build platform.

[0083] The extrusion nozzle can be initially positioned a predetermined height above the build platform to form the first layer of the three-dimensional structure. The height of each subsequent layer can be then closely controlled. In some examples, thinner layers result in an overall smoother surface.

[0084] Thicker layers can increase the speed at which the structure is built. Layers as thin as 0.0001 mm can be formed. The layers can be formed horizontally, vertically, or in any other orientation. Depositing of the resin can take place along any of the three axes. The dispensing of the resin can take place along only the "X" - "Y" plane, until it is advantageous to deposit in the "X" "Z" plane or the "Z" " Y" plane. In some examples, the extrusion nozzle can be mounted along generally perpendicular to the build platform, and thus perpendicular to the "X" - "Y" plane of build platform. The first layer can take any shape dictated by the computer program. A second and each subsequent layer can take slightly different shapes, as dictated by the particular cross section for each layer from the computer program and layering software. In the pattern situation for each layer wherein each layer is formed only in a horizontal "X" - "Y" plane. A motor supporting the extrusion nozzle can be selectively actuated after each layer is formed to raise the nozzle incrementally along the "Z" axis in a closely controlled manner. [0085] The multiple layers can be of uniform thickness, or the layers can vary in thickness, as necessary and appropriate for the forming of a particular structure. Also, the layers may each vary in thickness across the height of each layer.

[0086] Additive manufacturing systems build the solid part one layer at a time. Typical layer thicknesses range from about 0.001 to about 1,000,000 mm, from about 0.001 to about 1,000 mm, from about 0.001 to about 100 mm. Depending on the design, the layer can be thicker or thinner as practicable. The thickness can be adjusted depending on the process parameters, including the total number of layers that make up the structure, and the speed in which the structure is being built.

[0087] The device may operate generally according to a method comprising the following steps: inserting the filament into an additive manufacturing apparatus having a nozzle; heating the filament; and dispensing a fluid bead out of the filament out of the nozzle to manufacture a three-dimensional object.

[0088] When 3D printing thermoplastic polymers using additive manufacturing, the adhesion between the first printed layer and the printing bed can be crucial, since it provides the foundation to the subsequent layers. Inadequate adhesion can result in poor printing quality or destroyed bed surfaces. The optimal adhesion of the printed sample to the printing bed can be achieved by heating the printing bed at temperatures above glass transition temperature (Tg) of the filament material. Increasing the temperature above the filament's Tg leads to a reduction of the surface tension between the printing bed and the printing material and to a larger contact area that ultimately causes better adhesion between the bed and the filament. For 3D printing polyolefins, the build plate temperature range can be any temperature above Tg, and below Tm or degradation temperature (whatever is lower) of the printing filament. In some examples, the extrusion temperature is from 100 to 250°C, preferred from 120-240°C, more preferred froml55 to 230°C. The Extruder screw rotation speed can be from 30 to 50 RPM, preferred from 35 to 45 RPM, more preferred from 38 to 40 RPM.

[0089] The 3D printer nozzle temperature can be above the melting temperature and below the degradation temperature of the printing filament.

[0090] To prevent warping, 3D printed parts can have good adhesion to the build plate. Physical adjustments to ensure good adhesion between 3D printed parts and build plate can include one or more of the following:

(1) Using a heated build plate. When printing polymers, the build plate temperature can be around 25 °C.

(2) Applying an adhesive to the build plate. The commonly used adhesives for polyolefin include commercially available printing adhesive solution, or polyolefin based tapes.

(3) Ensure the build plate is leveled correctly. It can be important that the first print layer of a print is pressed firmly onto the glass plate, to allow it to bond properly. If the distance between the nozzle and build plate is too wide, the material can easily become loose.

(4) Ensure build plate surface is smooth and clean.

(5) Materials that require a high build plate temperature requires an isothermal printing environment. Cooler airflows from the environment can cause adhesion problems, and in extreme cases, may cause the print to separate from the build plate.

[0091] Software adjustments to help improve adhesion can include: 1) Use a “brim”. Placing a single-layer-thick flat area around the object can creating a larger adhesion surface. Print warping can be minimized by this. After printing, the brim can be removed easily.

2) Use a raft. For some materials or models, a brim might not be enough to prevent warping. In these instances, using a raft can be advisable. A raft can add a thick grid between the model and the build plate, ensuring that the heat is distributed equally. It is particularly useful when the bottom of a model is not completely flat, or when printing with industrial materials.

3) Two important settings (relating to the first layer) that influence adhesion are the initial layer height and initial layer speed. In some cases, a thicker initial layer can make adhesion easier, as build plate calibration is not as critical. It is important not to set the initial layer speed too high, as the material may attach to the nozzle and get dragged around with it, instead of remaining fixed to the build plate. Adjusting initial layer settings to use a low initial layer speed can ensure that the material has enough time to properly adhere to the build plate. For polyolefins, first layer printing speed can be around 6 mm/s.

4) Cooling can be one of the main causes of warping. Material contracts when cooling, and can cause the material to pull on itself. Materials can be cooled properly before the next layer is added, but excessive cooling should be avoided to ensure a smooth, warp-free print. For polyolefins, the recommended cooling can vary material by material.

[0092] In some examples, the 3-D component can contain from 2 to an unlimited number of engineered layers; from 2 to about 10,000 layers; from 2 to about 5,000 layers; from 2 to about 1,000 layers; from 2 to about 500 layers; from 2 to about 250 layers; from 2 to about 100 layers; from 10 to about 500 layers; from 50 to about 500 layers; from 100 to about 500 layers; or from 250 to about 500 layers. Each layer can have the same or different dimensions. Components having almost any shape can be prepared by additive manufacturing. In some examples, the 3D printed component can be personal protective devices, medical facemasks, masks, mask components, tubing, goggles, shoes, hats or ventilator components.

[0093] In some examples, the 3-D component can have a Notch Izod Impact at 29°C of at least 10, or 11, or 12 or 13, or 14, or 15 Ft*1bf/in. In some examples, the 3-D component can have aNotch Izod Impact at 29°C of from 10 to 20 Ft*1bf/in, from 10 to 18 Ft*1bf/in, from 12 to 20 Ft*1bf/in, from 12 to 18 Ft*1bf/in, from 12 to 17 Ft*1bf/in, from 13 to 20 Ft*1bf/in, from 13 to 18 Ft*1bf/in, from 13 to 17 Ft*1bf/in, from 14 to 20 Ft*1bf/in, from 14 to 18 Ft*1bf/in, or from 14 to 17 Ft*1bf/in. [0094] In some examples, the 3-D component can have a Flex Modulus of at least 100, or 150, or 175 or 200, or 225, or 250 MPa. In some examples, the 3-D component can have a Flex Modulus of from 100 to 400 MPa, from 100 to 300 MPa, from 100 to 275 MPa, from 175 to 400 MPa, from 175 to 300 MPa, from 175 to 275 MPa, from 200 to 400 MPa, from 200 to 300 MPa, from 200 to 275 MPa, from 225 to 400 MPa, from 225 to 300 MPa, from 225 to 275 MPa.

[0095] In some examples, the 3-D component can have a Strain at Break of at least 75, 100, 200, or 250, or 300 or 350, or 400, or 450%. In some examples, the 3-D component can have a Strain at Break of from 75 to 600%, from 100 to 550%, from 200 to 500%, from 300 to 600%, from 300 to 550%, from 300 to 500%, from 350 to 600%, from 350 to 550%, from 350 to 500%, from 400 to 600%, from 400 to 550%, or from 400 to 500%.

[0096] In some examples, the 3-D component can have a Modulus (1 % Secant) of at least 600, or 700, or 800 or 900, or 1,000 MPa. In some examples, the 3-D component can have a Modulus (1% Secant) of from 700 to 1,500 MPa, from 700 to 1,400 MPa, from 700 to 1,200 MPa, from 800 to 1,500 MPa, from 800 to 1,400 MPa, from 800 to 1,200 MPa, from 900 to 1,500 MPa, from 900 to 1,400 MPa, from 900 to 1,200 MPa, or from 1,000 to 1,400 MPa. [0097] In some examples, the 3-D component can have a Young’s Modulus of at least 600, or 700, or 800 or 900, or 1,000 MPa. In some examples, the 3-D component can have a Young’s Modulus of from 700 to 1,500 MPa, from 700 to 1,400 MPa, from 700 to 1,200 MPa, from 800 to 1,500 MPa, from 800 to 1,400 MPa, from 800 to 1,200 MPa, from 900 to 1,500 MPa, from 900 to 1,400 MPa, from 900 to 1,200 MPa, or from 1,000 to 1,400 MPa.

[0098] In some examples, the 3-D component can have a Tensile Stress at Yield of less than 30, 25, 20, 18, 16, 14, 12, 10 MPa. In some examples, the 3-D component can have a Tensile Stress at Yield of from 6 to 25 MPa, from 10 to 25 MPa, from 15 to 25 MPa, or from 20 to 25 MPa.

[0099] In some examples, the 3-D component can have a Tensile Stress at Break of at least

10, or 12, or 14 or 16, or 18 MPa. In some examples, the 3-D component can have a Tensile

Stress at Break of from 2 to 10 MPa, from 2 to 25 MPa, from 2 to 20 MPa, from 2 to 15 MPa, from 2 to 10 MPa, from 2 to 8 MPa, from 2 to 6 MPa, or from 2 to 4 MPa.

[0100] In one or more embodiments, the 3D objects prepared using the inventive additive manufacturing process has a heterogeneous morphology. As used herein, the term

“heterogeneous blend” means a composition having two or more morphological phases in the same state. For example, a blend of two polymers where one polymer forms discrete packets dispersed in a matrix or “continuous phase” of another polymer is said to be heterogeneous in the solid state. Also, a heterogeneous blend is defined to include co-continuous blends where the blend components are separately visible, but it is unclear which is the “continuous phase” and which is the discontinuous phase. Such morphology is determined using atomic force microscopy (AFM). In contrast, a “homogeneous blend” is a composition having substantially one morphological phase in the same state. For example, a blend of two polymers where one polymer is miscible with another polymer is said to be homogeneous in the solid state. By miscible is meant that that the blend of two or more polymers exhibits single-phase behavior for the glass transition temperature, e.g. the Tg would exist as a single sharp transition temperature on a dynamic mechanical thermal analyzer (DMTA) trace of tan d (i.e., the ratio of the loss modulus to the storage modulus) versus temperature. By contrast, two separate transition temperatures would be observed for an immiscible blend, typically corresponding to the temperatures for each of the individual components of the blend. Thus, a polymer blend is miscible when there is one Tg indicated on the DMTA trace. A miscible blend is homogeneous, while an immiscible blend is heterogeneous.

[0101] In one or more embodiments, the 3D objects are printed from a heterogeneous blend of the polyethylene and polar polymer that constitutes the continuous phase and particles of the polyethylene different from, and more crystalline than, the polar polymer dispersed within the continuous phase. The dispersed particles typically have an average size of less than 50 or 40 or 30 microns, for example in the range of about 50 nanometers to less than 50 microns. Preferably, the dispersed particles have an average size of less than 30 microns, such as less than 20 microns, for example less than or equal to 10 microns, for example between about 100 nanometers and about 10 microns.

[0102] In alternative embodiments, the 3D objects are printed from a heterogeneous blend of the polyethylene and polar polymer that constitutes discrete packets in the dispersed phase and particles of polar polymer different from, and less crystalline than, the polyethylene in the continuous matrix phase. The dispersed particles typically have an average size of less than 50 or 40 or 30 microns, for example in the range of about 50 nanometers to less than 50 microns. Preferably, the dispersed particles have an average size of less than 30 microns, such as less than 20 microns, for example less than or equal to 10 microns, for example between about 100 nanometers and about 10 microns.

[0103] This invention further relates to:

1. A process for making a three-dimensional object using an additive manufacturing process, comprising: preparing a blend comprising a polyethylene having a density of at least 0.94 g/cm³ and a polar copolymer; extruding the blend to make a filament; inserting the filament into an additive manufacturing apparatus having a nozzle; heating the filament; and dispensing a fluid bead of the filament out of the nozzle to manufacture the three- dimensional object.

2. The process of paragraph 1, wherein the fluid bead of the filament is dispensed out of the nozzle onto a heated build plate.

3. The process of paragraph 1 or paragraph 2, wherein the heated build plate has an adhesive applied to a surface of the heated build plate.

4. The process of any of paragraphs 1 to 3, wherein the polar polymer is an ethylene vinyl acetate copolymer.

5. The process of paragraph 4, wherein the ethylene vinyl acetate copolymer has a vinyl acetate content from 20 wt% to 30 wt% based on a weight of the ethylene vinyl acetate copolymer.

6. The process of any of paragraphs 1 to 5, wherein the polar polymer is polyethylene grafted with maleic anhydride.

7. The process of paragraph 6, wherein the polyethylene grafted with maleic anhydride comprises from 0.1 wt% to 5 wt% of maleic anhydride based on the weight of the polyethylene grafted with maleic anhydride.

8. The process of any of paragraphs 1 to 7, wherein the blend comprises from about 70 wt% to about 99 wt% of the polyethylene and from 1 wt% to 30 wt% of the polar polymer based on a total weight of the polyethylene and the polar polymer.

9. A process for making a filament, comprising: preparing a blend comprising a polyethylene having a density of at least 0.94 g/cm³and a polar polymer; extruding the blend to make a filament, wherein the filament has a diameter from about 0.01 mm to about lm; and collecting the filament on a spool.

10. The process of paragraph 9, wherein the spool collects the filament at a rate from about 0.001 m/s to about 0.5 m/s.

11. The process of paragraph 9 or paragraph 10, wherein the fluid bead of the filament is dispensed out of the nozzle onto a heated build plate.

12. The process of any of paragraphs 9 to 11 , wherein the heated build plate has an adhesive applied to a surface of the heated build plate.

13. The process of any of paragraphs 9 to 12, wherein the polar polymer is an ethylene vinyl acetate copolymer.

14. The process of paragraph 13, wherein the ethylene vinyl acetate copolymer has a vinyl acetate content from 20 wt% to 30 wt% based on a weight of the ethylene vinyl acetate copolymer.

15. The process of any of paragraphs 9 to 14, wherein the polar polymer is polyethylene grafted with maleic anhydride.

16. The process of paragraph 15, wherein the polyethylene grafted with maleic anhydride comprises from 0.1 wt% to 5 wt% of maleic anhydride based on the weight of the polyethylene grafted with maleic anhydride.

17. The process of any of paragraphs 9 to 16, wherein the blend comprises from about 70 wt% to about 99 wt% of the polyethylene and from 1 wt% to 30 wt% of the polar polymer based on a total weight of the polyethylene and the polar polymer.

18. A filament comprising, a blend of a polyethylene having a density of at least 0.94 g/cm³ and a polar polymer, wherein the filament has a diameter from about 1 mm to about 3 mm.

19. The filament of paragraph 18, wherein the diameter of the filament changes less than 0.1 mm per meter of the filament. 20. The process of paragraph 18 or paragraph 19, wherein the fluid bead of the filament is dispensed out of the nozzle onto a heated build plate.

21. The process of any of paragraphs 18 to 20, wherein the heated build plate has an adhesive applied to a surface of the heated build plate.

22. The process of any of paragraphs 18 to 21, wherein the polar polymer is an ethylene vinyl acetate copolymer.

23. The filament of paragraph 22, wherein the ethylene vinyl acetate copolymer has a vinyl acetate content from 20 wt% to 30 wt% based on a weight of the ethylene vinyl acetate copolymer.

24. The filament of any of paragraphs 18 to 23, wherein the polar polymer is polyethylene grafted with maleic anhydride.

25. The filament of paragraph 24, wherein the polyethylene grafted with maleic anhydride comprises from 0.1 wt% to 5 wt% of maleic anhydride based on the weight of the polyethylene grafted with maleic anhydride.

26. The filament of any of paragraphs 18 to 25, wherein the blend comprises from about 70 wt% to about 99 wt% of the polyethylene and from 1 wt% to 30 wt% of the polar polymer based on a total weight of the polyethylene and the polar polymer.

27. An article printed using the process of paragraph 1.

28. The article of paragraph 27 wherein the article is a mask or mask component.

EXAMPLES Test Methods

Dynamic Mechanical Analysis (DMA)

[0104] The glass transition temperature (T_g) is measured using dynamic mechanical analysis. This test provides information about the small-strain mechanical response of a sample as a function of temperature over a temperature range that includes the glass transition region and the visco-elastic region prior to melting. Specimens are tested using a commercially available DMA instrument (e.g., TA Instruments DMA 2980 or Rheometrics RSA) equipped with a dual cantilever test fixture. The specimen is cooled to -130°C then heated to 60°C at a heating rate of 2°C/min while subjecting to an oscillatory deformation at 0.1% strain and a frequency of 1 rad/sec. The output of these DMA experiments is the storage modulus (E’) and loss modulus (E”). The storage modulus measures the elastic response or the ability of the material to store energy, and the loss modulus measures the viscous response or the ability of the material to dissipate energy. The ratio of E"/E', called Tan-delta, gives a measure of the damping ability of the material; peaks in Tan-delta are associated with relaxation modes for the material. T_g is defined to be the peak temperature associated with the b-relaxation mode, which typically occurs in a temperature range of -80 to +20°C for polyolefins. In a heterophase blend, separate b-relaxation modes for each blend component may cause more than one T_g to be detected for the blend; assignment of the T_g for each component are preferably based on the T_g observed when the individual components are similarly analyzed by DMA (although slight temperature shifts are possible).

Gel Permeation Chromatography (GPC)

[0105] Unless otherwise indicated, the distribution and the moments of molecular weight (Mw, Mn, Mz, Mw/Mn, etc.), the comonomer content and the branching index (g'_vis) are determined by using a high temperature Gel Permeation Chromatography (Polymer Char GPC- IR) equipped with a multiple-channel band-filter based Infrared detector IR5 with a multiple- channel band filter based infrared detector ensemble IR5 with band region covering from about 2,700 cm^-1 to about 3,000 cm^-1 (representing saturated C-H stretching vibration), an 18-angle light scattering detector and a viscometer. Three Agilent PLgel 10-μm Mixed-B LS columns are used to provide polymer separation. Reagent grade 1, 2, 4-trichlorobenzene (TCB) (from Sigma-Aldrich) comprising ~300 ppm antioxidant butylated hydroxytoluene (BHT) is used as the mobile phase at a nominal flow rate of -1.0 mL/min and a nominal injection volume of ~200 μL. The whole system including transfer lines, columns, and detectors is contained in an oven maintained at ~145°C. A given amount of sample is weighed and sealed in a standard vial with ~10 μL flow marker (heptane) added thereto. After loading the vial in the auto- sampler, the oligomer or polymer is dissolved in the instrument with -8 mL added TCB solvent at ~160°C with continuous shaking. The sample solution concentration is from -0.2 to -2.0 mg/ml, with lower concentrations used for higher molecular weight samples. The concentration, c, at each point in the chromatogram can be calculated from the baseline subtracted IR5 broadband signal, /, using the equation: c=αl, where α is the mass constant determined with polyethylene or polypropylene standards. The mass recovery can be calculated from the ratio of the integrated area of the concentration chromatography over elution volume and the injection mass which is equal to the pre-determined concentration multiplied by injection loop volume. The conventional molecular weight (IR MW) is determined by combining universal calibration relationship with the column calibration which is performed with a series of monodispersed polystyrene (PS) standards ranging from 700 to 10M gm/mole. The MW at each elution volume is calculated with following equation:

where the variables with subscript “PS” stand for polystyrene while those without a subscript are for the test samples. In this method, aps = 0.67 and Kps = 0.000175, a and K for other materials are as calculated in the published in literature (Sun, T. et al. Macromolecules 2001, 34, 6812), except that for purposes of this invention and claims thereto, a = 0.695+(0.01*(wt. fraction propylene)) and K = 0.000579-(0.0003502*(wt. fraction propylene)) for ethylene- propylene copolymers, a = 0.695 and K = 0.000579 for other linear ethylene polymers, a = 0.705 and K = 0.0002288 for linear propylene polymers. Concentrations are expressed in g/cm³, molecular weight is expressed in g/mole, and intrinsic viscosity (hence K in the Mark- Houwink equation) is expressed in dL/g unless otherwise noted.

[0106] The comonomer composition is determined by the ratio of the IR5 detector intensity corresponding to CH₂ and CH₃ channel calibrated with a series of PE and PP homo/copolymer standards whose nominal value are predetermined by NMR or FTIR. In particular, this provides the methyls per 1,000 total carbons (CH₃/1000TC) as a function of molecular weight. The short-chain branch (SCB) content per 1,000TC (SCB/1000TC) is then computed as a function of molecular weight by applying a chain-end correction to the CH₃/1000TC function, assuming each chain to be linear and terminated by a methyl group at each end. The weight % comonomer is then obtained from the following expression in which / is 0.3, 0.4, 0.6, 0.8, and so on for C₃, C₄, C₅, C₆, and so on co-monomers, respectively: w2 = f * SCB/1000TC.

[0107] The bulk composition of the polymer from the GPC-IR and GPC-4D analyses is obtained by considering the entire signals of the CH₃ and CEE channels between the integration limits of the concentration chromatogram. First, the following ratio is obtained

[0108] Then the same calibration of the CFb and CFb signal ratio, as mentioned previously in obtaining the CH₃/1000TC as a function of molecular weight, is applied to obtain the bulk CH₃/1000TC. A bulk methyl chain ends per lOOOTC (bulk CH₃ end/1000TC) is obtained by weight-averaging the chain-end correction over the molecular-weight range. Then w2b = f * bulk CH₃/1000TC bulk SCB/1000TC = bulk CH₃/1000TC - bulk CH₃end/1000TC and bulk SCB/1000TC is converted to bulk w2 in the same manner as described above.

[0109] The LS detector is the 18-angle Wyatt Technology High Temperature DAWN HELEOSII. The LS molecular weight (M) at each point in the chromatogram is determined by analyzing the LS output using the Zimm model for static light scattering ( Light Scattering from Polymer Solutions; Huglin, M. B., Ed.; Academic Press, 1972.):

Here, ΔR(θ) is the measured excess Rayleigh scattering intensity at scattering angle θ, c is the polymer concentration determined from the IR5 analysis, A₂ is the second virial coefficient,

P(θ) is the form factor for a monodisperse random coil, and K_O is the optical constant for the system:

where N_A is Avogadro's number, and (dn/dc) is the refractive index increment for the system. The refractive index, n = 1.500 for TCB at 145 C and λ = 665 nm. For analyzing polyethylene homopolymers, ethylene-hexene copolymers, and ethylene-octene copolymers, dn/dc = 0.1048 ml/mg and A₂ = 0.0015; for analyzing ethylene-butene copolymers, dn/dc = 0.1048*(1-0.00126*w2) ml/mg and A₂ = 0.0015 where w2 is weight percent butene comonomer.

[0110] A high temperature Agilent (or Viscotek Corporation) viscometer, which has four capillaries arranged in a Wheatstone bridge configuration with two pressure transducers, is used to determine specific viscosity. One transducer measures the total pressure drop across the detector, and the other, positioned between the two sides of the bridge, measures a differential pressure. The specific viscosity, η_s. for the solution flowing through the viscometer is calculated from their outputs. The intrinsic viscosity, [h], at each point in the chromatogram is calculated from the equation [h]= η_s/c. where c is concentration and is determined from the IR5 broadband channel output. The viscosity MW at each point is calculated as , where α_ps is 0.67 and K_ps is 0.000175.

[0111] The branching index (g'_vis) is calculated using the output of the GPC-IR5-LS-VIS method as follows. The average intrinsic viscosity, [η]_avg, of the sample is calculated by:

where the summations are over the chromatographic slices, i, between the integration limits.

The branching index g'_vis is defined as , where M_v is the viscosity-average

molecular weight based on molecular weights determined by LS analysis and the K and a are for the reference linear polymer, which are, for purposes of this invention and claims thereto, α = 0.695+(0.01*(wt. fraction propylene)) and K = 0.000579-(0.0003502*(wt. fraction propylene) for ethylene-propylene copolymers, a = 0.695 and K = 0.000579 for other linear ethylene polymers, α = 0.705 and K = 0.0002288 for linear propylene polymers. Concentrations are expressed in g/cm³, molecular weight is expressed in g/mole, and intrinsic viscosity (hence K in the Mark-Houwink equation) is expressed in dL/g unless otherwise noted. Calculation of the w2b values is as discussed above.

Differential Scanning Calorimetry (DSC)

[0112] The procedure for DSC determinations is as follows. 0.5 grams of polymer is weighed and pressed to a thickness of 15 to 20 mils (about 381-508 microns) at 140°C-150°C, using a “DSC mold” and MYLAR™ film as a backing sheet. The pressed polymer sample is allowed to cool to ambient temperatures by hanging in air (the MYLAR™ film backing sheet is not removed). The pressed polymer sample is then annealed at room temperature (about 23°C-25°C). A 15-20 mg disc is removed from the pressed polymer sample using a punch die and is placed in a 10 microliter aluminum sample pan. The disc sample is then placed in a DSC (Perkin Elmer Pyris 1 Thermal Analysis System) and is cooled to -100°C. The sample is heated at 10°C/min to attain a final temperature of 165°C. The thermal output, recorded as the area under the melting peak of the disc sample, is a measure of the heat of fusion and is expressed in Joules per gram (J/g) of polymer and is automatically calculated by the Perkin Elmer system. Under these conditions, the melting profile shows two (2) maxims, the maxima at the highest temperature is taken as the melting point within the range of melting of the disc sample relative to a baseline measurement for the increasing heat capacity of the polymer as a function of temperature. The percent crystallinity (X%) is calculated using the formula: [area under the curve (in J/g) / H° (in J/g)] * 100, where H° is the heat of fusion for the homopolymer of the maj or monomer component. The values for H° are to be obtained from the Polymer Handbook, Fourth Edition, published by John Wiley and Sons, New York 1999, except that a value of 290 J/g is used as the equilibrium heat of fusion (H°) for 100% crystalline polyethylene, a value of 140 J/g is used as the equilibrium heat of fusion (H°) for 100% crystalline polybutene, and a value of 207 J/g (H°) is used as the heat of fusion for a 100% crystalline polypropylene.

Other Test methods

[0113] Unless otherwise noted all melting points (T_m) are DSC second melt.

[0114] Melt Flow Rate (MFR) is determined according to ASTM D 1238-13 (230°C/2.16 kg).

[0115] Melt index (MI) is determined according to ASTM D 1238-13 (190°C/2.16kg). [0116] Environmental Stress Cracking (ESCR) is determined according to ASTM D 1693 15

Example 1

Filament fabrication description

[0117] Filaments of all examples were prepared using ThermoFisher Process 11 Parallel Twin-Screw Extruder, and spooler. The extrusion and spooler conditions used are tabulated in Table 2. Extrusion is a process used to create objects of a fixed cross-sectional profile. In a typical extrusion process, a material is pushed through a die of the desired cross-section. For each filament, 200 gm weight of the example resins in pellet form were fed into the extruder hopper, and then extruded out from a circular die with 3 mm diameter. By controlling the takeoff speed of the spooler, the diameter of the filament is adjusted to be 2.85 mm ± 0.1 mm measured by Neiko 01407A Electronic Digital Caliper.

FDM printed parts preparation and 3D printing process description

[0118] All Fused Deposition Modeling (FDM) specimens were fabricated with an Airwolf3D^® Axiom Single Head 3-D Printer. The geometry for the specimens investigated in this patent were ISO 37 Type 3 tensile bars. Dassault Systems SolidWorks software, which is a computer-aided design (CAD) package, was first used to create 3D printable model with the dimension of ISO 37 Type 3 tensile bar. Then, the CAD model is tessellated and exported in STL format. The STL file was then sliced using Repetier Host software from Hot-World GmbH & Co. KG to convert the STL file into G-code, which is the standard language for 3D printers. G-code is a numerically controlled programming language that contains commands to move parts within the printer. After filament is loaded to the 3D printer, and 3D printer is set up following printing conditions tabulated in Table 2, the FDM specimens were able to be produced. The properties of the FDM specimens are listed in Table 3.

Table 1: Resin properties.

Injection molding description

[0119] In order to measure the reference strength and behavior of the filament materials, for comparisons with FDM, additional specimens were fabricated by injection molding. Mold cavity dimensions were the same as those described for the FDM specimens, which is the ISO 37 Type 3 Tensile bar. All molded specimens were fabricated from the same FDM example resin pellets. The pellets were then fed into the hopper of a BOY XS injection molding machine. Molding parameters were set to the industrial recommended values for example resins, including nozzle temperature mold preheat temperature of 120°C, clamping force of 71 kN (16,000 1b), and injection pressure of 41 MPa (6,000 psi). Ten replicate specimens were molded for each of tests. [0120] Tensile and flexural tests were performed on an Instron Autox750 Automatic

Contacting Extensometer with 0.001 N force accuracy. The machine has a lOkN load force capacity. Instron Bluehill software was used to record the data. All materials are injection molded or 3D printed into IS037 Type 3 bar dimensions. Tensile measurements use ASTM D638-14 protocol, with stretching speed of 1.0 mm/min and span of 30 mm. Flexural measurements use ASTM D790-17 protocol.

Table 2

Table 3: Tensile property and flexural properties for parts at indicated manufacturing process.

Claims

CLAIMS:

What is claimed is:

1. A process, comprising: preparing a blend comprising a polyethylene having a density of at least 0.94 g/cm³ and a polar polymer; and extruding the blend to make a filament.

2. The process of claim 1, further comprising: inserting the filament into an additive manufacturing apparatus having a nozzle; heating the filament; and dispensing a fluid bead of the filament out of the nozzle to manufacture the three- dimensional object.

3. The process of claim 2, wherein the heated build plate has an adhesive applied to a surface of the heated build plate.

4. The process of any preceding claim, wherein the polar polymer is an ethylene vinyl acetate copolymer.

5. The process of claim 4, wherein the ethylene vinyl acetate copolymer has a vinyl acetate content from 20 wt% to 30 wt% based on a weight of the ethylene vinyl acetate copolymer.

6. The process of claim 1, wherein the polar polymer is polyethylene grafted with maleic anhydride.

7. The process of any preceding claim, wherein the polyethylene grafted with maleic anhydride comprises from 0.1 wt% to 5 wt% of maleic anhydride based on the weight of the polyethylene grafted with maleic anhydride.

8. The process of any preceding claim, wherein the blend comprises from about 70 wt% to about 99 wt% of the polyethylene and from 1 wt% to 30 wt% of the polar polymer based on a total weight of the polyethylene and the polar polymer.

9. The process of claim 2, wherein the filament has a diameter from about 0.01 mm to about 1 m, and the method further comprises: collecting the filament on a spool.

11. The process of claim 9, wherein the fluid bead of the filament is dispensed out of the nozzle onto a heated build plate.

12. The process of claim 9, wherein the heated build plate has an adhesive applied to a surface of the heated build plate.

13. A filament comprising, a blend of a polyethylene having a density of at least 0.94 g/cm³ and a polar polymer, wherein the filament has a diameter from about 1 mm to about 3 mm.

14. The filament of claim 13, wherein the polar polymer is an ethylene vinyl acetate copolymer.

15. The filament of claim 14, wherein the ethylene vinyl acetate copolymer has a vinyl acetate content from 20 wt% to 30 wt% based on a weight of the ethylene vinyl acetate copolymer.