ADDITIVE MANUFACTURING PROCESS USING PRINTING MATERIAL OF UNEQUAL COMPOSITION, AND ARTICLE OBTAINABLE BY SAID PROCESS

TECHNICAL FIELD

[0001] The present disclosure relates to the field of additive manufacturing and to the field of polymeric materials used in additive manufacturing.

BACKGROUND

[0002] Plastic articles are formed from compositions that may contain functional additives. These additives perform important functions and are, out of necessity, added to the bulk of the composition before or during extrusion. This is inefficient, as the need for these additives is primarily at the surface of the article formed from the composition and not throughout the bulk of the article.

[0003] Coatings are the most common way to provide desired additives in high concentration at the surface of a part. Coatings present a number of disadvantages, however, including the need for an extra manufacturing step (and the associated extra cost), the challenge of providing good adhesion of the coating to the article, as well as the environmentally hostile use of solvents. Multi-layer extrusion of a capstock over a base layer of polymer requires good melt strength of both layers, such that they can be extruded, as well as good interlay er adhesion. High levels of additives in plastics, however, can lower the melt strength of the plastic, making this approach impossible or lowering the yield of finished goods.

[0004] These and other shortcomings are addressed by aspects of the present disclosure.

SUMMARY

[0005] In meeting the described needs, the present disclosure first provides articles, the article comprising a first polymer portion and a second polymer portion, the first and second polymer portions contacting one another, the first polymer portion having a solubility parameter S I, the second polymer portion having a solubility parameter S2, and (SI - S2) ² < 2, and the first polymer portion comprising a first polymer portion additive.

[0006] The present disclosure also provides methods, the methods comprising: by way of an additive manufacturing process, forming a second polymer portion in contact with a first polymer portion, the first polymeric portion having a solubility parameter SI, the second polymer portion having a solubility parameter S2, and (S I - S2) ² < 2, and one of the first and second polymer portions comprising a first additive. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIG. 1 provides an exemplary cutaway view of an article according to the present disclosure.

[0008] FIG. 2 provides an exemplary cutaway view of an alternative article according to the present disclosure.

[0009] FIG. 3 provides an exemplary cutaway view of a further article according to the present disclosure.

[0010] FIGS. 4A-C are structures of exemplary ultraviolet absorbing compositions.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0011] The present disclosure may be understood more readily by reference to the following detailed description of desired aspects and the examples included herein. In the following specification and the claims that follow, reference will be made to a number of terms which have the following meanings.

[0012] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present disclosure. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

[0013] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0014] As used in the specification and in the claims, the term "comprising" may include the embodiments "consisting of and "consisting essentially of." The terms

"comprise(s)," "include(s)," "having," "has," "can," "contain(s)," and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named ingredients/steps and permit the presence of other ingredients/steps. However, such description should be construed as also describing compositions or processes as "consisting of and "consisting essentially of the enumerated ingredients/steps, which allows the presence of only the named ingredients/steps, along with any impurities that might result therefrom, and excludes other ingredients/steps.

[0015] Numerical values in the specification and claims of this application, particularly as they relate to polymers or polymer compositions, reflect average values for a composition that may contain individual polymers of different characteristics. Furthermore, unless indicated to the contrary, the numerical values should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

[0016] All ranges disclosed herein are inclusive of the recited endpoint and

independently combinable (for example, the range of "from 2 grams to 10 grams" is inclusive of the endpoints, 2 grams and 10 grams, and all the intermediate values). The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and/or values.

[0017] As used herein, approximating language may be applied to modify any quantitative representation that may vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as "about" and "substantially," may not be limited to the precise value specified, in some cases. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. The modifier "about" should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the expression "from about 2 to about 4" also discloses the range "from 2 to 4." The term "about" may refer to plus or minus 10% of the indicated number. For example, "about 10%" may indicate a range of 9% to 11 %, and "about 1 " may mean from 0.9-1.1. Other meanings of "about" may be apparent from the context, such as rounding off, so, for example "about 1" may also mean from 0.5 to 1.4.

[0018] As explained herein, plastic articles are formed from compositions that often contain functional additives. The additives are typically added to the bulk of the material during extrusion, despite the fact that the need for these additives is primarily at the surface of an article formed from the material and not throughout the bulk of the article. Although coating techniques are a popular way to provide additives at relatively high concentration at the surface of a part, coatings present a number of disadvantages, including the need for costly manufacturing steps, the challenge of adhering the coating to the part, and the use of solvents.

[0019] In meeting these long-felt needs, the present disclosure provides a method of producing an article having different concentrations of functional additives or polymers as a function of location (e.g., depth) within the article. The disclosed technology provides, inter alia, additive manufacturing methods in which adjacent layers share a base material (e.g., a resin) but differ in terms of the level of one or more additives that are present in one or more of the adjacent layers. [0020] Exemplary Additives

[0021] A variety of additives may be present in the disclosed compositions. Some exemplary, non-limiting additive classes (e.g., antioxidants, flame retardants) are provided below.

[0022] UV stabilizers and UV absorbers

[0023] The compositions of the present disclosure may comprise an ultraviolet (UV) stabilizer for dispersing UV radiation energy. A UV stabilizer may be selected that does not substantially hinder or prevent cross-linking of the various components of the compositions of the disclosure. UV stabilizers include, e.g., hydroxybenzophenones; hydroxyphenyl benzotriazoles; cyanoacrylates; oxanilides; or hydroxyphenyl triazines. Specific UV stabilizers include poly[(6-mo hilino-s-triazine-2,4-diyl)[2,2,6,6-tetramethyl-4-piperidyl) imino]- hexamethylene [(2,2,6,6-tetramethyl-4-piperidyl)imino] , 2-hydroxy-4-octyloxybenzophenone (Uvinul®3008); 6-tert-butyl-2-(5-chloro-2H-benzotriazole-2-yl)-4-methylphen yl (Uvinul® 3026); 2,4-di-tert-butyl-6-(5-chloro-2H-benzotriazole-2-yl)-phenol (Uvinul®3027); 2-(2H- benzotriazole-2-yl)-4,6-di-tert-pentylphenol (Uvinul®3028); 2-(2H-benzotriazole-2-yl)-4- (l,l,3,3-tetramethylbutyl)-phenol (Uvinul® 3029); l,3-bis[(2'-cyano-3',3'- dipheny lacry loy l)oxy ] -2,2-bis- { [(2' -cy ano-3 ' ,3 ' -dipheny lacry loy l)oxy] methyl } -propane (Uvinul® 3030); 2-(2H-benzotriazole-2-yl)-4-methylphenol (Uvinul® 3033); 2-(2H- benzotriazole-2-yl)-4,6-bis(l -methyl- 1-pheny ethyl) phenol (Uvinul® 3034); ethyl-2-cyano-3,3- diphenylacrylate (Uvinul® 3035); (2-ethylhexyl)-2-cyano-3,3-diphenylacrylate (Uvinul® 3039); N,N'-bisformyl-N,N'-bis (2,2,6,6-tetramethyl-4-piperidinyl)hexamethylenediamine (Uvinul® 4050H); bis-(2,2,6,6-tetramethyl-4-pipieridyl)-sebacate (Uvinul® 4077H); bis-(l, 2,2,6,6- pentamethyl-4-piperdiyl)-sebacate + methyl-(l ,2,2,6,6-pentamethy l-4-piperidyl)-sebacate (Uvinul® 4092H); or combinations thereof. Other UV stabilizers include Cyasorb 5411™, Cyasorb UV-3638™, Uvinul 3030™, and/or Tinuvin 234™

[0024] The compositions may also include one or more UV absorbers. Exemplary UV absorbers include ZnO and T1O2. The ZnO and TiC may be present in nanoparticle form, i.e., having a cross-sectional dimension (e.g., diameter, width, height, thickness) of from about 1 nm to about 100 nm.

[0025] Heat stabilizers

[0026] The compositions of the disclosure may comprise heat stabilizers. Exemplary heat stabilizer additives include, for example, organophosphites such as triphenyl phosphite, tris- (2,6-dimethylphenyl)phosphite, tris-(mixed mono-and di-nonylphenyl)phosphite or the like; phosphonates such as dimethylbenzene phosphonate or the like; phosphates such as trimethyl phosphate, or the like; or combinations thereof.

[0027] Antistatic agents

[0028] The compositions of the disclosure may comprise an antistatic agent. Examples of monomeric antistatic agents may include glycerol monostearate, glycerol distearate, glycerol tristearate, ethoxylated amines, primary, secondary and tertiary amines, ethoxylated alcohols, alkyl sulfates, alkylarylsulfates, alkylphosphates, alkylaminesulfates, alkyl sulfonate salts such as sodium stearyl sulfonate, sodium dodecylbenzenesulfonate or the like, quaternary ammonium salts, quaternary ammonium resins, imidazoline derivatives, sorbitan esters, ethanolamides, betaines, or the like, or combinations comprising at least one of the foregoing monomeric antistatic agents.

[0029] Exemplary polymeric antistatic agents may include certain polyesteramides polyether-polyamide (polyetheramide) block copolymers, polyetheresteramide block

copolymers, polyetheresters, or polyurethanes, each containing polyalkylene glycol moieties polyalkylene oxide units such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like. Such polymeric antistatic agents are commercially available, for example PELESTAT® 6321 (Sanyo) or PEBAX® MH1657 (Atofina), IRGASTAT® P18 and P22 (Ciba- Geigy). Other polymeric materials may be used as antistatic agents are inherently conducting polymers such as polyaniline (commercially available as PANIPOL®EB from Panipol), polypyrrole and polythiophene (commercially available from Bayer), which retain some of their intrinsic conductivity after melt processing at elevated temperatures. Carbon fibers, carbon nanofibers, carbon nanotubes, carbon black, or a combination comprising at least one of the foregoing may be included to render the compositions of the disclosure electrostatically dissipative.

[0030] Anti-drip agents

[0031] The compositions of the disclosure may comprise anti-drip agents. The anti- drip agent may be a fibril forming or non-fibril forming fluoropolymer such as

polytetrafluoroethylene (PTFE). The anti-drip agent can be encapsulated by a rigid copolymer as described above, for example styrene-acrylonitrile copolymer (SAN). PTFE encapsulated in SAN is known as TSAN. Encapsulated fiuoropolymers can be made by polymerizing the encapsulating polymer in the presence of the fluoropolymer, for example an aqueous dispersion. TSAN can provide significant advantages over PTFE, in that TSAN can be more readily dispersed in the composition. An exemplary TSAN can comprise 50 wt% PTFE and 50 wt% SAN, based on the total weight of the encapsulated fluoropolymer. The SAN can comprise, for example, 75 wt% styrene and 25 wt% acrylonitrile based on the total weight of the copolymer. Alternatively, the fluoropolymer can be pre-blended in some manner with a second polymer, such as for, example, an aromatic polycarbonate or SAN to form an agglomerated material for use as an anti-drip agent. Either method can be used to produce an encapsulated fluoropolymer.

[0032] Radiation stabilizers

[0033] The compositions of the disclosure may comprise a radiation stabilizer, such as a gamma-radiation stabilizer. Exemplary gamma-radiation stabilizers include alkylene polyols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,4-butanediol, meso- 2,3-butanediol, 1,2-pentanediol, 2,3-pentanediol, 1,4-pentanediol, 1 ,4-hexandiol, and the like; cycloalkylene polyols such as 1,2-cyclopentanediol, 1,2-cyclohexanediol, and the like; branched alkylenepolyols such as 2,3-dimethyl-2,3-butanediol (pinacol), and the like, as well as alkoxy- substituted cyclic or acyclic alkanes. Unsaturated alkenols are also useful, examples of which include 4-methyl-4-penten-2-ol, 3-methyl-pentene-3-ol, 2-methyl-4-penten-2-ol, 2,4-dimethyl-4- penten-2-ol, and 9 to decen-l-ol, as well as tertiary alcohols that have at least one hydroxy substituted tertiary carbon, for example 2-methyl-2,4-pentanediol (hexylene glycol), 2-phenyl-2- butanol, 3-hydroxy-3-methyl-2-butanone, 2-phenyl-2-butanol, and the like, and cyclic tertiary alcohols such as 1 -hydroxy- 1-methyl-cyclohexane. Certain hydroxymethyl aromatic compounds that have hydroxy substitution on a saturated carbon attached to an unsaturated carbon in an aromatic ring can also be used. The hydroxy-substituted saturated carbon can be a methylol group (-CH2OH) or it can be a member of a more complex hydrocarbon group such as - CR ²⁴ HOH or -CR ²⁴ 20H wherein R ²⁴ is a complex or a simple hydrocarbon. Specific hydroxy methyl aromatic compounds include benzhydrol, 1,3-benzenedimethanol, benzyl alcohol, 4- benzyloxy benzyl alcohol and benzyl benzyl alcohol. 2-Methyl-2,4-pentanediol, polyethylene glycol, and polypropylene glycol are often used for gamma-radiation stabilization.

[0034] Pigments

[0035] The term "pigments" means colored particles that are insoluble in the resulting compositions of the disclosure. Exemplary pigments include titanium oxide, carbon black, carbon nanotubes, metal particles, silica, metal oxides, metal sulfides or any other mineral pigment; phthalocyanines, anthraquinones, quinacridones, dioxazines, azo pigments or any other organic pigment, natural pigments (madder, indigo, crimson, cochineal, etc.) and mixtures of pigments. The pigments may represent from 0.05% to 15% by weight relative to the weight of the overall composition. [0036] Dyes

[0037] The term "dye" refers to molecules that are soluble in the compositions of the disclosure and that have the capacity of absorbing part of the visible radiation.

[0038] Fibers

[0039] Exemplary fibers include glass fibers, carbon fibers, polyester fibers, polyamide fibers, aramid fibers, cellulose and nanocellulose fibers or plant fibers (linseed, hemp, sisal, bamboo, etc.) and combinations thereof.

[0040] Pigments, dyes or fibers capable of absorbing radiation may be used to ensure the heating of an article based on the compositions of the disclosure when heated using a radiation source such as a laser, or by the Joule effect, by induction or by microwaves. Such heating may allow the use of a process for manufacturing, transforming or recycling an article made of the compositions of the disclosure.

[0041] Fillers

[0042] Suitable fillers for the compositions of the disclosure include: silica, clays, calcium carbonate, carbon black, kaolin, and whiskers. Other possible fillers include, for example, silicates and silica powders such as aluminum silicate (mullite), synthetic calcium silicate, zirconium silicate, fused silica, crystalline silica graphite, natural silica sand, or the like; boron powders such as boron-nitride powder, boron-silicate powders, or the like; oxides such as Ti02, aluminum oxide, magnesium oxide, or the like; calcium sulfate (as its anhydride, dihydrate or trihydrate); calcium carbonates such as chalk, limestone, marble, synthetic precipitated calcium carbonates, or the like; talc, including fibrous, modular, needle shaped, lamellar talc, or the like; wollastonite; surface-treated wollastonite; glass spheres such as hollow and solid glass spheres, silicate spheres, cenospheres, aluminosilicate (armospheres), or the like; kaolin, including hard kaolin, soft kaolin, calcined kaolin, kaolin comprising various coatings known in the art to facilitate compatibility with the polymeric matrix, or the like; single crystal fibers or "whiskers" such as silicon carbide, alumina, boron carbide, iron, nickel, copper, or the like; fibers (including continuous and chopped fibers) such as asbestos, carbon fibers, glass fibers, such as E, A, C, ECR, R, S, D, or NE glasses, or the like; sulfides such as molybdenum sulfide, zinc sulfide or the like; barium compounds such as barium titanate, barium ferrite, barium sulfate, heavy spar, or the like; metals and metal oxides such as particulate or fibrous aluminum, bronze, zinc, copper and nickel or the like; flaked fillers such as glass flakes, flaked silicon carbide, aluminum diboride, aluminum flakes, steel flakes or the like; fibrous fillers, for example short inorganic fibers such as those derived from blends comprising at least one of aluminum silicates, aluminum oxides, magnesium oxides, and calcium sulfate hemihydrate or the like; natural fillers and reinforcements, such as wood flour obtained by pulverizing wood, fibrous products such as cellulose, cotton, sisal, jute, starch, cork flour, lignin, ground nut shells, corn, rice grain husks or the like; organic fillers such as polytetrafluoroethylene; reinforcing organic fibrous fillers formed from organic polymers capable of forming fibers such as poly(ether ketone), polyimide, polybenzoxazole, poly(phenylene sulfide), polyesters, polyethylene, aromatic polyamides, aromatic polyimides, polyetherimides, polytetrafluoroethylene, acrylic resins, poly(vinyl alcohol) or the like; as well as additional fillers and reinforcing agents such as mica, clay, feldspar, flue dust, fillite, quartz, quartzite, perlite, tripoli, diatomaceous earth, carbon black, or the like, or combinations comprising at least one of the foregoing fillers or reinforcing agents.

[0043] Plasticizers. lubricants, and mold release agents

[0044] Plasticizers, lubricants, and mold release agents can be included. Mold release agent (MRA) will allow the material to be removed quickly and effectively. Mold releases can reduce cycle times, defects, and browning of finished product. There is considerable overlap among these types of materials, which may include, for example, phthalic acid esters such as dioctyl-4,5-epoxy-hexahydrophthalate; tris-(octoxycarbonylethyl)isocyanurate; tristearin; di- or polyfunctional aromatic phosphates such as resorcinol tetraphenyl diphosphate (RDP), the bis(diphenyl) phosphate of hydroquinone and the bis(diphenyl) phosphate of bisphenol-A; poly- alpha-olefins; epoxidized soybean oil; silicones, including silicone oils; esters, for example, fatty acid esters such as alkyl stearyl esters, e.g., methyl stearate, stearyl stearate, pentaerythritol tetrastearate (PETS), and the like; combinations of methyl stearate and hydrophilic and hydrophobic nonionic surfactants comprising polyethylene glycol polymers, polypropylene glycol polymers, poly(ethylene glycol-co-propylene glycol) copolymers, or a combination comprising at least one of the foregoing glycol polymers, e.g., methyl stearate and polyethylene- polypropylene glycol copolymer in a suitable solvent; waxes such as beeswax, montan wax, paraffin wax, or the like.

[0045] Flame retardants

[0046] Various types of flame retardants can be utilized as additives. In one aspect, the flame retardant additives include, for example, flame retardant salts such as alkali metal salts of perfluorinated C1-C 16 alkyl sulfonates such as potassium perfluorobutane sulfonate (Rimar salt), potassium perfluoroctane sulfonate, tetraethylammonium perfluorohexane sulfonate, potassium diphenylsulfone sulfonate (KSS), and the like, sodium benzene sulfonate, sodium toluene sulfonate (NATS) and the like; and salts formed by reacting for example an alkali metal or alkaline earth metal (for example lithium, sodium, potassium, magnesium, calcium and barium salts) and an inorganic acid complex salt, for example, an oxo-anion, such as alkali metal and alkaline-earth metal salts of carbonic acid, such as Na2C03, K2CO3, MgCCb, CaCC , and BaCC or fluoro-anion complex such as L13AIF6, BaSiF6, KBF4, K3AIF6, KAIF4, K2S1F6, and/or Na3AlF6 or the like. Rimar salt and KSS and NATS, alone or in combination with other flame retardants, are particularly suitable for the disclosed compositions. In certain aspects, the flame retardant does not contain bromine or chlorine.

[0047] The flame retardant additives may include organic compounds that include phosphorus, bromine, and/or chlorine. In certain aspects, the flame retardant is not a bromine or chlorine containing composition. Non-brominated and non-chlorinated phosphorus-containing flame retardants can include, for example, organic phosphates and organic compounds containing phosphorus-nitrogen bonds. Exemplary di- or polyfunctional aromatic phosphorus- containing compounds include resorcinol tetraphenyl diphosphate (RDP), the bis(diphenyl) phosphate of hydroquinone and the bis(diphenyl) phosphate of bisphenol-A, respectively, their oligomeric and polymeric counterparts, and the like. Other exemplary phosphorus-containing flame retardant additives include phosphonitrilic chloride, phosphorus ester amides, phosphoric acid amides, phosphonic acid amides, phosphinic acid amides, tris(aziridinyl) phosphine oxide, polyorganophosphazenes, and polyorganophosphonates.

[0048] Some suitable polymeric or oligomeric flame retardants include: 2,2-bis-(3,5- dichlorophenyl)-propane; bis-(2-chlorophenyl)-methane; bis(2,6-dibromophenyl)-methane; 1,1- bis-(4-iodophenyl)-ethane; l,2-bis-(2,6-dichlorophenyl)-ethane; l,l-bis-(2-chloro-4- iodophenyl)ethane; l,l-bis-(2-chloro-4-methylphenyl)-ethane; l,l-bis-(3,5-dichlorophenyl)- ethane; 2,2-bis-(3-phenyl-4-bromophenyl)-ethane; 2,6-bis-(4,6-dichloronaphthyl)-propane; 2,2- bis-(2,6-dichlorophenyl)-pentane; 2,2-bis-(3,5-dibromophenyl)-hexane; bis-(4-chlorophenyl)- phenyl-methane; bis-(3,5-dichlorophenyl)-cyclohexylmethane; bis-(3-nitro-4-bromophenyl)- methane; bis-(4-hydroxy-2,6-dichloro-3-methoxyphenyl)-methane; 2,2-bis-(3,5-dichloro-4- hydroxyphenyl)-propane; and 2,2-bis-(3-bromo-4-hydroxyphenyl)-propane. Other flame retardants include: 1,3-dichlorobenzene, 1,4-dibromobenzene, l,3-dichloro-4-hydroxybenzene, and biphenyls such as 2,2 '-dichlorobi phenyl, polybrominated 1,4-diphenoxy benzene, 2,4'- dibromobiphenyl, and 2,4'-dichlorobiphenyl as well as decabromo diphenyl oxide, and the like.

[0049] The flame retardant optionally is a non-halogen based metal salt, e.g., of a monomeric or polymeric aromatic sulfonate or mixture thereof. The metal salt is, for example, an alkali metal or alkali earth metal salt or mixed metal salt. The metals of these groups include sodium, lithium, potassium, rubidium, cesium, beryllium, magnesium, calcium, strontium, francium and barium. Examples of flame retardants include cesium benzenesulfonate and cesium p-toluenesulfonate. See e.g., US 3,933,734, EP 2103654, and US2010/0069543A1, the disclosures of which are incorporated herein by reference in their entirety.

[0050] Another useful class of flame retardant is the class of cyclic siloxanes having the general formula [(R)2SiO] _y wherein R is a monovalent hydrocarbon or fluorinated hydrocarbon having from 1 to 18 carbon atoms and y is a number from 3 to 12. Examples of fluorinated hydrocarbon include, but are not limited to, 3-fluoropropyl, 3,3,3-trifluoropropyl, 5,5,5,4,4,3,3- heptafluoropentyl, fluorophenyl, difluorophenyl and trifluorotolyl. Examples of suitable cyclic siloxanes include, but are not limited to, octamethylcyclotetrasiloxane, 1,2,3,4-tetramethyl- 1,2,3,4-tetravinylcyclotetrasiloxane, l,2,3,4-tetramethyl-l,2,3,4-tetraphenylcyclotetrasiloxane, octaethylcyclotetrasiloxane, octapropylcyclotetrasiloxane, octabutylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane,

tetradecamethylcycloheptasiloxane, hexadecamethylcyclooctasiloxane,

eicosamethylcyclodecasiloxane, octaphenylcyclotetrasiloxane, and the like. A particularly useful cyclic siloxane is octaphenylcyclotetrasiloxane.

[0051] Antioxidants

[0052] Exemplary antioxidant additives include organophosphites such as tris(nonyl phenyl)phosphite, tris(2,4-di-t-butylphenyl)phosphite ("IRGAFOS 168" or "1-168"), bis(2,4-di-t- but lphenyl)pentaerythritol diphosphite, distearyl pentaerythritol diphosphite or the like;

alkylated monophenols or polyphenols; alkylated reaction products of polyphenols with dienes, such as tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate )] methane, or the like; butylated reaction products of para-cresol or dicyclopentadiene; alkylated hydroquinones;

hydroxylated thiodiphenyl ethers; alkylidene-bisphenols; benzyl compounds; esters of beta-(3,5- di-tert-butyl-4-hydroxyphenyl)-propionic acid with monohydric or polyhydric alcohols; esters of beta-(5-tert-butyl-4-hydroxy-3-methylphenyl)-propionic acid with monohydric or polyhydric alcohols; esters of thioalkyl or thioaryl compounds such as distearylthiopropionate,

dilaurylthiopropionate, ditridecylthiodipropionate, octadecyl-3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate, pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate or the like; amides of beta-(3,5-di-tert-butyl-4-hydroxyphenyl)- propionic acid or the like, or combinations comprising at least one of the foregoing antioxidants.

[0053] Exemplary Aspects

[0054] A cutaway view of an exemplary article is shown in FIG. 1. An article according to FIG. 1 may be fabricated by, e.g., a 3D printer that features multiple nozzles, which nozzles are capable of dispensing materials of varied composition. (One such example is the Rova3D 5 Extruder™, which unit has 5 nozzles.) In this way, materials that are compatible with one another, or nearly identical, can be layered adjacent to one another. The composition of an article, as a function of part thickness, can thus be varied by using 3D filaments of differing composition. This disclosed approach is especially applicable when the outer surface of an article would benefit from having a functional additive that offers little advantage when found deep within the article. Examples of such additives are UV stabilizing additives, antistatic additives, surface energy modifying additives, nano-particles, and additives or polymers that affect chemical, electrical, and scratch resistance.

[0055] A user may create a support structure or utilize an existing support structure (e.g., a moveable base). A 3D printer may, with a first nozzle, print on that support structure a base material. A second nozzle, dispensing a material that comprises the based material but also includes an amount of an additive that is different from the base material, may print a second layer, e.g., a capping layer atop the based material. It should be understood, of course, that the same nozzle may be used to dispense first, second, third, and other materials. Because the base material and capping layer are similar in composition, there will be improved adhesion between the layers (interlay er adhesion).

[0056] Examples of the types of functionality introduced by a part accordingly to FIG. 1 include increased UV resistance (weatherability), chemical resistance, scratch resistance, antistatic properties, surface energy modification (hydrophilic/hydrophobic differences), laser marking properties, and wear resistance, among others; a variety of illustrative additives are described elsewhere herein.

[0057] An exemplary base material could be, e.g., acrylonitrile styrene acrylate (ASA) resin with a first level of UV stabilizing additives. The outer capping layer may comprise ASA with a higher concentration of UV stabilizing additives. It should be understood that while the outermost layer of an article may have a higher concentration of a given additive than an inner layer of the article, the outermost layer of an article may have a lower concentration of a given additive than an inner layer of the article.

[0058] Examples of articles having the profile shown in FIG. 1 are automotive side- view mirror housings and roofing tiles, among other articles where UV absorbance at the exterior of the article is of importance. In some aspects, the exterior of the article may have a level of an additive that is from 0.001 to 100% (and all intermediate values) greater than the level of the additive at another location within the article. For example, an automotive mirror housing may have a UV absorber present in the outermost layer of the article of, e.g., 10 wt%. An interior layer of the article (e.g., a layer that is not exposed to the environment exterior to the article) may have a level of the UV absorber that is only, e.g., 0.5 wt%. It should be understood that two adjacent layers may have different levels of two or more additives. For example, an exterior layer of a mirror housing may have a UV absorber present at 10 wt% and a scratch-resistant additive present at 5 wt%, and an interior layer of the same housing may have the UV absorber present at 0.5 wt% and a scratch-resistant additive present at 0 wt%.

[0059] The disclosed technology is thus particularly useful for application where two surfaces of an article may be exposed to different environments, e.g., a conduit where the exterior of an article is exposed to sunlight and where the interior of the article is exposed to a particular fluid. By application of the disclosed technology, a user may construct an article with the desired characteristics, e.g., where the exterior surface of the conduit comprises a suitable level of UV absorber, and wherein the interior surface of the conduit comprises an additive that confers the on the article resistance to degradation from the fluid.

[0060] The disclosed technology also provides for articles with an exemplary side cutaway profile shown in FIG. 2. In this illustrative figure, the first layer (base material) is covered, or surrounded, by the second layer. (In one example aspect, to produce such a side profile, two nozzles dispensing the different materials may print at the level of the same layer. For example, at the level of the dashed line in the middle of the FIG. 2 side profile and moving from left to right, a first nozzle may print some of the Cap Layer material, followed by a second nozzle printing the Base Material, and then the first nozzle (or even a third nozzle) printing more of the Cap Layer material. In this way, a user may fabricate an article that has a core-shell cross- sectional profile, e.g., a central core that is encased in one or more layers.

[0061] It should be noted that the concentration difference of the functional additive of the disclosure extends beyond the scenario where the outer surface contains a higher amount of the functional additive than the core. The reverse scenario, where the core contains a higher amount of the functional additive, is also envisioned. As but one example, the disclosed technology may be used to produce an article that has an ASA first (inner) layer and an ASA second (outer) layer, where the second (outer) layer has a higher concentration of UV

absorbing/stabilizing additives than the first layer.

[0062] An example article having the side profile shown in FIG. 2 is one in which the core material is a compostable resin such as PLA (polylactic acid) or polycaprolactone, the core material further comprising an additive (such as SiC ) that promotes or accelerates

compostability or biodegradation. The capping (or exterior) layer material would contain less or even none of this additive. The outer layer would therefore have higher environmental stability, yet an article with this compositional structure would undergo more rapid composting than a part that was comprised entirely of PLA (or polycaprolactone) without the composting accelerating additive. Examples of such articles are forks and spoons, which may be fabricated such that they have a core region that undergoes composting at a faster rate than the outer, surrounding or enrobing layer.

[0063] An article according to the present disclosure may comprise 2, 3, 4, 5, 6, 7, 8, 9, 10, or more layers. An article may comprise 100, 200, or even more layers, depending on the needs of the user. It should be understood that an article may include two or more layers (not necessarily adj acent to one another) that are identical in composition. Layers may vary in thickness, e.g., a layer may be from 0.1 to 100 mm in thickness (and all intermediate values). Adjacent layers may be of the same or different thicknesses.

[0064] UV Absorber Applications

[0065] The presently disclosed technology has particular utility in applications that require UV absorbance. Thermoplastics, including polycarbonate, suffer from the drawback that they are not weatherable to outdoor exposure conditions, i.e. they may crack and/or change color. Although coatings exist to overcome this problem, they are not satisfactory for a variety of reasons, including the use of environmentally-unfriendly solvents and also the difficulty in controlling coating thickness, which lack of control can lead to variable weathering performance. In addition, coating an injection molded part requires that a mold for such injection molding be prepared first, which mold preparation can be costly and time consuming.

[0066] Additive manufacturing techniques, such as fused deposition modeling (FDM), do not require that a mold be made, and such techniques are thus well-suited for rapid part fabrication. A user who wishes to fabricate an article that has characteristics that are achieved by addition of additives must, however, either (1) disperse those additives throughout the bulk of the article; or (2) dispose those additives in a coating that is separately (and inefficiently/ expensively) disposed on the article.

[0067] With particular relation to article that feature UV absorption performance, biphenyl triazine (BPT) UV absorbers represent the state of the art in high efficiency organic UV stabilizers. Existing methods of forming articles that include such additives, however, are known to produce variations in thickness that can compromise the weathering performance of the multi- layered system, leading to coating failure. As described elsewhere herein, multi-layer extrusion of a capstock over a base layer of polymer requires good melt strength of both layers, such that they can be extruded, as well as good interlayer adhesion. High levels of additives in plastics can lower their melt strength, making this approach impossible or lowering the yield of finished goods. [0068] As one example of a UV -tolerant article according to the present disclosure, a multi-layer product is prepared by firstly 3D printing a thermoplastic base, as an example polycarbonate (PC) or an ASA-PC (ASA is an acrylonitrile-styrene-acrylate) resin. Next, a first portion comprising a biphenyl triazine UV absorbing compound is deposited on the base. As a preferred example, this portion may comprise an ASA resin (including an ASA-PC resin) that comprises within the biphenyl triazine UV absorbing compound. This portion may be a monolayer. Using fused deposition modelling (FDM) equipment, suitable starting materials may be a polycarbonate filament (containing an optional UV absorber) (base) and an ASA filament containing biphenyl triazine (BPT) (first portion). The BPT in the ASA layer may be present in an amount between 0.5 - 20 wt%, based on the total weight of all components in the layer.

[0069] An illustration of such a multi-layer system, having a BPT-containing layer on one or both sides of the exemplary polycarbonate, is shown below in FIG. 3, which figure illustrates an article with improved weathering performance. The ASA layer may be thicker than the thermoplastic (polycarbonate) layer, e.g., at least 10 times thicker. The ASA layer can be a monolayer, and may have a thickness of from about 0.1 to about 100 millimeter (mm), e.g., from about 0.1 to about 50 mm, from about 0.1 to about 25 mm, or even from about 0.1 to about 10 mm, or from about 0.1 to about 0.5 mm. The thickness of a layer may be determined by processing conditions, including the thickness of an additive manufacturing filament used to make the layer.

[0070] Without being bound to any particular theory, an ASA layer containing BPT may exhibit improved adhesion to an ASA/PC substrate, as compared to adhesion to a substrate that is free of ASA. The generic structure of an exemplary biphenyl triazine UV absorbing compound is shown in FIG. 4A; particularly suitable BPT UV absorbers are exemplified by the chemical structures in FIG. 4B and 4C.

[0071] Illustrative Aspects

[0072] The following aspects are illustrative only and do not limit the scope of the present disclosure or the scope of the attached claims.

[0073] Aspect 1 A. An article, comprising: a first polymeric portion having first and second surfaces, the first polymeric portion comprising a first polymer and a first additive present at a first loading level; and a second polymeric portion contacting the first surface of the first polymeric portion, the second polymeric portion comprising the first polymer of the first polymeric portion and further comprising the first additive, the first additive being present in the second polymeric portion at a second loading level, the second loading level differing from the first loading level. [0074] Aspect IB. An article, consisting of: a first polymeric portion having first and second surfaces, the first polymeric portion comprising a first polymer and a first additive present at a first loading level; and a second polymeric portion contacting the first surface of the first polymeric portion, the second polymeric portion comprising the first polymer of the first polymeric portion and further comprising the first additive, the first additive being present in the second polymeric portion at a second loading level, the second loading level differing from the first loading level.

[0075] Aspect 1C. An article, consisting essentially of: a first polymeric portion having first and second surfaces, the first polymeric portion comprising a first polymer and a first additive present at a first loading level; and a second polymeric portion contacting the first surface of the first polymeric portion, the second polymeric portion comprising the first polymer of the first polymeric portion and further comprising the first additive, the first additive being present in the second polymeric portion at a second loading level, the second loading level differing from the first loading level.

[0076] The first polymeric portion may be present as a layer. Suitable additives include, e.g., ultraviolet stabilizing additives; other suitable additives are described elsewhere herein.

[0077] The second polymeric portion suitably shares at least one polymer component in common with the first polymeric portion. As but one example, the first and second polymeric portions may both comprise ASA resin. The second polymeric portion also suitably shares at least one additive in common with the first polymeric portion, e.g., both polymeric portions have the same ultraviolet absorber. The relative amounts of the first polymer in the first and second portions may be the same (e.g., both portions may comprise 75 wt% ASA), but the relative amounts may also differ (e.g., ASA is present at 60 wt% in the first portion and at 88 wt% in the second portion).

[0078] The relative amounts of the first additive in the first and second portions may differ. For example, an additive may be present at 0 wt% in the first portion but be present at 25 wt% in the second portion. It should be understood that a polymeric portion may have a zero wt% loading of an additive.

[0079] Aspect 2. The article of any of aspects 1A-1C, further comprising a third polymeric portion, the third polymeric portion contacting the second surface of the first polymeric portion, the third polymeric portion comprising the first polymer of the first polymeric portion, the third polymeric portion further comprising the first additive, the first additive being present in the third polymeric portion at a third loading level, the third loading level differing from the first loading level.

[0080] Aspect 3. The article of any of aspects 1 A-2, wherein the first polymer comprises a thermoplastic.

[0081] Aspect 4. The article of aspect 3, wherein the thermoplastic comprises acrylonitrile styrene acrylate, polycarbonate, polylactic acid, polycaprolactone, or any combination thereof.

[0082] Aspect 5. The article of any of aspects 1 A-4, wherein the first additive comprises an ultraviolet absorber, a biodegradation promoter, an impact modifier, an adhesion promoter, or any combination thereof. Additives that confer one or more of chemical resistance (e.g., a crystalline polymer, such as PBT), scratch resistance, anti-static properties, surface energy modification (hydrophilic/hydrophobic differences), laser marking properties, flame retardants, and wear resistance are all considered suitable additives. Again, suitable additives are described elsewhere herein.

[0083] Aspect 6. The article of aspect 5, wherein the first additive comprises a biphenyl triazine.

[0084] Aspect 7. The article of any of aspects 1 A -2, wherein the second polymeric portion comprises a second polymer. The second polymer may differ from the first polymer; e.g., the first polymer may comprise PLA, and the second polymer may comprise ASA.

[0085] Aspect 8. The article of aspect 7, wherein the third polymeric portion comprises the second polymer.

[0086] Aspect 9. The article of any of aspects 7-8, wherein the second polymer comprises a thermoplastic.

[0087] Aspect 10. The article of any of aspects 1A -9, wherein the first polymer portion has a solubility parameter Si, the second polymer portion has a solubility parameter S ₂ , and (Si - S2) ² < 2. Solubility parameters may be calculated according to the Hildebrand method, e.g., at pages 61-66 of Barton's Handbook of Solubility Parameters and Other Cohesion

Parameters (1983), the disclosure of which is incorporated by this reference herein in its entirety. In some aspects, the relationship between the solubility of adjacent layers X and Y (where layer X has a solubility parameter Sx and layer Y has a solubility parameter SY) may be expressed as (Sx - SY) ² < 2; i.e. , adjacent layers are formed of compositions that satisfy the foregoing relationship.

[0088] Aspect 11. The article of any of aspects 1 A -9, wherein the first polymer is present in the second polymeric portion at a weight percentage of the second polymeric portion that is within about 90% of the weight percentage at which the first polymer is present in the first polymeric portion. In some aspects, the first polymer is present in the second polymeric portion at a weight percentage of the second polymeric portion that is within about 5% of the weight percentage at which the first polymer is present in the first polymeric portion.

[0089] Aspect 12. The article of any of aspects 1 A -11, wherein the first polymer is present in the third polymeric portion at a weight percentage of the second polymeric portion that is within 90% of the weight percentage at which the first polymer is present in the first polymeric portion.

[0090] Aspect 13. The article of aspect 12, wherein the first polymer is present in the third polymeric portion at a weight percentage of the second polymeric portion that is within 5% of the weight percentage at which the first polymer is present in the first polymeric portion.

[0091] Aspect 14. The article of any of aspects 1A -13, wherein the second loading level of the first additive is greater than the first loading level of the first additive.

[0092] Aspect 15. The article of any of aspects 1A-13, wherein the second loading level of the first additive is less than the first loading level of the first additive.

[0093] Aspect 16. The article of aspect 2, wherein the third loading level of the first additive is greater than the first loading level of the first additive.

[0094] Aspect 17. The article of aspect 2, wherein the third loading level of the first additive is less than the first loading level of the first additive.

[0095] Aspect 18. The article of any of aspects 1A-17, further comprising a coating layer surmounting the article, the coating layer being characterized as providing an improvement in one or more of abrasion-resistance, a scratch-resistance, or any combination thereof. The improvement may be measured by, e.g., measuring haze or gloss on samples before and after a Taber abrasion test.

[0096] Aspect 19. The article of any of aspects 1A-18, wherein the first polymer portion defines a thickness in the range of from about 0.1 to about 100 mm, or from about 0.1 to about 50 mm, or from about 0.1 to about 25 mm, or from about 0.1 to about 10 mm.

[0097] Aspect 20. The article of any of aspects 1A-19, wherein the first and second loading levels are nonzero and wherein the ratio of the first loading level to the second loading level is from about 1 : 10,000 to about 10,000: 1, e.g., from about 1 : 1000 to about 1000: 1, from about 1 :500 to about 500: 1, from about 1 :200 to about 200: 1, from about 1 : 100 to about 100: 1, or from about 1 :50 to about 50: 1, or from about 1 : 10 to about 10: 1, or from about 1 :2 to about 2: 1. [0098] Aspect 21. The article of aspect 2, wherein the first and third loading levels are nonzero and wherein the ratio of the first loading level to the third loading level is from about 1 : 10,000 to about 10,000: 1 , e.g., from about 1 : 1000 to about 1000: 1 , from about 1 :500 to about 500: 1 , from about 1 :200 to about 200: 1, from about 1 : 100 to about 100: 1 , or from about 1 :50 to about 50: 1, or from about 1 : 10 to about 10: 1 , or from about 1 :2 to about 2: 1.

[0099] Aspect 22. The article of any of aspects 1A-21 , wherein the first loading level is from about 0.001 to about 90 wt% as measured against the overall weight of the first polymeric portion, e.g., from about 0.1 to about 80 wt%, from about 1 to about 70 wt%, from about 5 to about 60 wt%, from about 10 to about 50 wt% from about 20 to about 40 wt%.

[00100] Aspect 23. The article of any of aspects 1A-22, wherein the second loading level is from about 0.001 to about 90 wt% as measured against the overall weight of the first polymeric portion, e.g., from about 0.1 to about 80 wt%, from about 1 to about 70 wt%, from about 5 to about 60 wt%, from about 10 to about 50 wt% from about 20 to about 40 wt%.

[00101] Aspect 24. The article of any of aspects 1A-23, wherein the third loading level, when present, is from about 0.001 to about 90 wt% as measured against the overall weight of the first polymeric portion, e.g., from about 0.1 to about 80 wt%, from about 1 to about 70 wt%, from about 5 to about 60 wt%, from about 10 to about 50 wt% from about 20 to about 40 wt%.

[00102] Aspect 25. The article of aspect 2, further comprising a fourth polymeric portion, the fourth polymer portion contacting the second polymeric portion, the third polymeric portion, or both, the fourth polymeric portion comprising the first polymer of the first polymeric portion, the fourth polymeric portion further comprising the first additive, the first additive being present in the fourth polymeric portion at a fourth loading level, the fourth loading level differing from the second loading level, the third loading level, or both.

[00103] Aspect 26A. A method, comprising: disposing a first polymeric portion comprising a first polymer and a first additive present at a first loading level; and disposing a second polymeric portion comprising the first polymer and the first additive present at a second loading level, the second polymeric portion contacting the first polymeric portion, the second loading level differing from the first loading level, and the disposing being effected so as to form at least a portion of an article.

[00104] Aspect 26B. A method, consisting of: disposing a first polymeric portion comprising a first polymer and a first additive present at a first loading level; and disposing a second polymeric portion comprising the first polymer and the first additive present at a second loading level, the second polymeric portion contacting the first polymeric portion, the second loading level differing from the first loading level, and the disposing being effected so as to form at least a portion of an article.

[00105] Aspect 26C. A method, consisting essentially of: disposing a first polymeric portion comprising a first polymer and a first additive present at a first loading level; and disposing a second polymeric portion comprising the first polymer and the first additive present at a second loading level, the second polymeric portion contacting the first polymeric portion, the second loading level differing from the first loading level, and the disposing being effected so as to form at least a portion of an article.

[00106] It should be understood that in some aspects, the first and second polymeric portions may be fused or otherwise connected to one another. It should also be understood that these methods may be performed in an additive manufacturing process.

[00107] An article may be made by, e.g., layers from a thermoplastic material such as string of pellets or filament from a digital model by selectively dispensing through a nozzle or orifice.

[00108] One suitable additive manufacturing process is fused deposition modeling (FDM), which is an additive manufacturing technology that uses thermoplastic monofilaments, pellets, or metal wires to build parts or articles in a layer-by-layer manner. In some FDM aspects, material from a spool is fed by an extrusion nozzle that is heated to melt the material, which melted material is then controllably deposited in the horizontal and vertical directions.

[00109] Material jetting is another suitable additive manufacturing technique for the disclosed technology. A material jetting process creates objects in a manner similar to an ink jet printer, whereby build material is dispensed onto a substrate (e.g., platform) in a continuous or drop-wise fashion.

[00110] Powder bed fusion processes are also suitable. In such processes (e.g., selective laser sintering or SLS), an energy source melts and then fuses particulate material together to form solidified regions (e.g., layers). The energy source (e.g., a laser) is directed according to a pre-set schedule of locations and intensities. A variety of mechanisms may be used to spread powder over previously-sintered regions, including rollers and blades. A hopper or other reservoir beneath or nearby to the bed of material being solidified is suitably used to provide fresh material for further rounds of sintering.

[00111] Other suitable additive manufacturing techniques are described in ASTM F2792-12a.

[00112] Aspect 27. The method of any of aspects 26A-26C, further comprising disposing a third polymeric portion, the third polymeric portion comprising the first additive, the first additive being present in the third polymeric portion at a third loading level that differs from the first loading level, and the third polymeric portion contacting the first polymeric portion, the second polymeric portion, or both.

[00113] Aspect 28. The method of any of aspects 26A-27, wherein the first polymer portion has a solubility parameter Si, the second polymer portion has a solubility parameter S ₂ , and (Si - S2) ² < 2. Solubility parameters may be calculated according to the Hildebrand method, e.g., at pages 61-66 of Barton's Handbook of Solubility Parameters and Other Cohesion

Parameters (1983), the disclosure of which is incorporated by this reference herein in its entirety.

[00114] Aspect 29. The method of any of aspects 26A-28, wherein the first polymer is present in the second polymeric portion at a weight percentage of the second polymeric portion that is within about 90% of the weight percentage at which the first polymer is present in the first polymeric portion.

[00115] Aspect 30. The method of any of aspects 26A-29, wherein the first polymer is present in the third polymeric portion, if present, at a weight percentage of the third polymeric portion that is within 90% of the weight percentage at which the first polymer is present in the first polymeric portion.

[00116] Aspect 31. The method of any of aspects 26A-30, further comprising disposing a coating layer surmounting the article, the coating layer being characterized as providing an improvement in one or more of abrasion-resistance, a scratch-resistance, or any combination thereof. The improvement may be measured by, e.g., measuring haze or gloss on samples before and after a Taber abrasion test.

[00117] Aspect 32. The method of any of aspects 26A-31, wherein the first polymer comprises a thermoplastic.

[00118] Aspect 33. The method of aspect 32, wherein the thermoplastic comprises acrylonitrile styrene acrylate, polycarbonate, polylactic acid, polycaprolactone, or any combination thereof.

[00119] Aspect 34. The method of any of aspects 26A-33, wherein the first additive comprises an ultraviolet absorber, a biodegradation promoter, an impact modifier, an adhesion promoter, or any combination thereof.

[00120] Aspect 35. The method of any of aspects 26A-34, wherein the disposing is effected so as to form an entire article.

[00121] Aspect 36. The method of any of aspects 26A-35, wherein the first additive comprises an ultraviolet absorber, a biodegradation promoter, an impact modifier, an adhesion promoter, or any combination thereof. [00122] Aspect 37. The method of aspect 36, wherein the first additive comprises a biphenyl triazine.

[00123] Aspect 38. The method of any of aspects 26A-37, wherein the second polymeric portion comprises a second polymer.

[00124] Aspect 39. The method of aspect 38, wherein the third polymeric portion comprises the second polymer.

[00125] Aspect 40. The method of any of aspects 38-39, wherein the second polymer comprises a thermoplastic.

[00126] Aspect 41. The method of any of aspects 26A-40, wherein the second loading level of the first additive is greater than the first loading level of the first additive.

[00127] Aspect 42. The method of any of aspects 26A-41, wherein the second loading level of the first additive is less than the first loading level of the first additive.

[00128] Aspect 43. The method of aspect 27, wherein the third loading level of the first additive is greater than the first loading level of the first additive.

[00129] Aspect 44. The method of aspect 27, wherein the third loading level of the first additive is less than the first loading level of the first additive.

[00130] Aspect 45. The method of any of aspects 26A-44, wherein the first polymer portion defines a thickness in the range of from about 0.1 to about 100 mm, or from about 0.1 to about 50 mm, or from about 0.1 to about 25 mm, or from about 0.1 to about 10 mm.

[00131] Aspect 46. The method of any of aspects 26A-45, wherein the first and second loading levels are nonzero and wherein the ratio of the first loading level to the second loading level is from about 1 : 10,000 to about 10,000: 1, e.g., from about 1 : 1000 to about 1000: 1, from about 1 :500 to about 500: 1, from about 1 :200 to about 200: 1, from about 1 : 100 to about 100: 1, or from about 1 :50 to about 50: 1, or from about 1 : 10 to about 10: 1, or from about 1 :2 to about 2: 1.

[00132] Aspect 47. The method of any of aspects 27-46, wherein the first and third loading levels are nonzero and wherein the ratio of the first loading level to the third loading level is from about 1 : 10,000 to about 10,000: 1, e.g., from about 1 : 1000 to about 1000: 1, from about 1 :500 to about 500: 1, from about 1 :200 to about 200: 1, from about 1 : 100 to about 100: 1, or from about 1 :50 to about 50: 1, or from about 1 : 10 to about 10: 1, or from about 1 :2 to about 2: 1.

[00133] Aspect 48. The method of any of aspects 26A-47, wherein the first loading level is from about 0.001 to about 90 wt% as measured against the overall weight of the first polymeric portion, e.g., from about 0.1 to about 80 wt%, from about 1 to about 70 wt%, from about 5 to about 60 wt%, from about 10 to about 50 wt% from about 20 to about 40 wt%.

[00134] Aspect 49. The method of any of aspects 26A-48, wherein the second loading level is from about 0.001 to about 90 wt% as measured against the overall weight of the first polymeric portion, e.g., from about 0.1 to about 80 wt%, from about 1 to about 70 wt%, from about 5 to about 60 wt%, from about 10 to about 50 wt% from about 20 to about 40 wt%.

[00135] Aspect 50. The article of any of aspects 27-49, wherein the third loading level, when present, is from about 0.001 to about 90 wt% as measured against the overall weight of the first polymeric portion, e.g., from about 0.1 to about 80 wt%, from about 1 to about 70 wt%, from about 5 to about 60 wt%, from about 10 to about 50 wt% from about 20 to about 40 wt%.

[00136] Aspect 51. The method of any of aspects 26A-50, further comprising a fourth polymeric portion, the fourth polymer portion contacting the second polymeric portion, the third polymeric portion, or both, the fourth polymeric portion comprising the first polymer of the first polymeric portion, the fourth polymeric portion further comprising the first additive, the first additive being present in the fourth polymeric portion at a fourth loading level, the fourth loading level differing from the second loading level, the third loading level, or both.

[00137] Aspect 52A. An article, comprising: a first polymeric portion having first and second surfaces, the first polymeric portion comprising a thermoplastic that comprises acrylonitrile styrene acrylate, polycarbonate, or any combination thereof; and a second polymeric portion contacting the first polymeric portion, the second polymeric portion comprising the thermoplastic of the first polymeric portion, the second polymeric portion comprising an amount of a biphenyl triazine.

[00138] Aspect 52B. An article, consisting of: a first polymeric portion having first and second surfaces, the first polymeric portion comprising a thermoplastic that comprises acrylonitrile styrene acrylate, polycarbonate, or any combination thereof; and a second polymeric portion contacting the first polymeric portion, the second polymeric portion comprising the thermoplastic of the first polymeric portion, the second polymeric portion comprising an amount of a biphenyl triazine.

[00139] Aspect 52C. An article, consisting essentially of: a first polymeric portion having first and second surfaces, the first polymeric portion comprising a thermoplastic that comprises acrylonitrile styrene acrylate, polycarbonate, or any combination thereof; and a second polymeric portion contacting the first polymeric portion, the second polymeric portion comprising the thermoplastic of the first polymeric portion, the second polymeric portion comprising an amount of a biphenyl triazine. [00140] In some aspects, the first polymer portion has a solubility parameter S i, the second polymer portion has a solubility parameter S ₂ , and (S i - S2) ² < 2. Solubility parameters may be calculated according to the Hildebrand method, e.g., at pages 61-66 of Barton's

Handbook of Solubility Parameters and Other Cohesion Parameters (1983), the disclosure of which is incorporated by this reference herein in its entirety.

[00141] In some aspects, the thermoplastic is present in the second polymeric portion at a weight percentage of the second polymeric portion that is within about 90% of the weight percentage at which the thermoplastic is present in the first polymeric portion.

[00142] Aspect 53. The article of any of aspects 52A-52C, further comprising a third polymeric portion, the third polymeric portion contacting the first polymeric portion, the second polymeric portion, or both, the third polymeric portion comprising the thermoplastic of the first polymeric portion, the third polymeric portion comprising an amount of a biphenyl triazine.

[00143] In some aspects, the thermoplastic is present in the third polymeric portion at a weight percentage of the third polymeric portion that is within about 90% of the weight percentage at which the thermoplastic is present in the first polymeric portion. The third polymeric portion may have a solubility parameter S3. The square of the difference between S i and S2 may be less than about 2. The square of the difference between Si and S3 may be less than about 2.

[00144] Aspect 54A. An article, comprising: a first polymer portion and a second polymer portion, the first and second polymer portions contacting one another, the first polymer portion having a solubility parameter SI, the second polymer portion having a solubility parameter S2, and (SI - S2) ² < 2, and the first polymer portion comprising a first polymer portion additive.

[00145] Aspect 54B. An article, consisting of: a first polymer portion and a second polymer portion, the first and second polymer portions contacting one another, the first polymer portion having a solubility parameter SI, the second polymer portion having a solubility parameter S2, and (SI - S2) ² < 2, and the first polymer portion comprising a first polymer portion additive.

[00146] Aspect 54B. An article, consisting essentially of: a first polymer portion and a second polymer portion, the first and second polymer portions contacting one another, the first polymer portion having a solubility parameter SI, the second polymer portion having a solubility parameter S2, and (SI - S2) ² < 2, and the first polymer portion comprising a first polymer portion additive. [00147] Aspect 55. The article of any of aspects 54A-54C, wherein the first polymer portion comprises at least one of an acrylonitrile styrene acrylate (ASA), a polycarbonate, a polylactic acid, a polycaprolactone, or any combination thereof. ASA is considered especially suitable.

[00148] Aspect 56. The article of any of aspects 54A-55, wherein the second polymer portion comprises at least one of an acrylonitrile styrene acrylate, a polycarbonate, a polylactic acid, a polycaprolactone, or any combination thereof.

[00149] Aspect 57. The article of any of aspects 54A-56, wherein the first polymer portion additive is characterized as being in the class of a UV absorber, a UV stabilizer, a heat stabilizer, an antistatic agent, an anti-drip agent, a radiation stabilizer, a pigment, a dye, a filler, a fiber, a plasticizer, a lubricant, a mold release agent, a flame retardant, an antioxidant, or a combination thereof.

[00150] Aspect 58. The article of any of aspects 54A-57, wherein the second polymer portion comprises a second polymer portion additive.

[00151] Aspect 59. The article of aspect 58, wherein the second polymer portion additive is of the same class as the first polymer portion additive. As one example, the first and second polymer portion additives may both be flame retardants, but are not necessarily the same flame retardant. As another example, the first and second polymer portion additives are both the same flame retardant.

[00152] Aspect 60. The article of any of aspects 58-59, wherein the percentage, by weight, of the first polymer portion additive in the first polymer portion differs from the percentage, by weight, of the second polymer portion additive in the second polymer portion.

[00153] As one example, a given additive may be present in the first polymer portion at about 5 wt%, and the same additive may be present in the second polymer portion at around 3 wt%. As another example, the first polymer portion additive may be present in the first polymer portion at around 10 wt%, and the second polymer portion additive (which may be of the same additive class as the first polymer portion additive or may even be the same as the first polymer portion additive) may be present in the second polymer portion at around 8 wt%.

[00154] Aspect 61. The article of any of aspects 54A-60, wherein at least one of the first and second polymer portions defines a thickness in the range of from about 0.01 to about 10 mm, e.g. , about 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or even about 10 mm, and all intermediate values. [00155] Aspect 62. The article of aspect 61, wherein at least one of the first and second polymer portions defines a thickness in the range of from about 0.1 to about 1 mm, e.g., 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or about 1 mm.

[00156] Aspect 63. The article of any of aspects 54A-62, wherein the first polymer portion additive comprises a biphenyl triazine.

[00157] Aspect 64. The article of any of aspects 54A-63, wherein the first and second polymer portions comprise an acrylonitrile styrene acrylate, the first and second polymer portions comprise a polycarbonate, the first and second polymer portions comprise a polylactic acid (PLA), or the first and second polymer portions comprise a polycaprolactone.

[00158] As an illustrative example, the first and second polymer portions may both comprise polycarbonate (PC). It is not a requirement, however, that both the first and second polymer portions comprise the same PC, i.e. , the first polymer portion may comprise a first PC that differs in molecular weight, molecular formula, or both from the PC of the second polymer portion. In some aspects, the first and second polymer portions may comprise the same polymer, e.g. , the same PC.

[00159] Aspect 65A. A method, comprising: by way of an additive manufacturing process, forming a second polymer portion in contact with a first polymer portion, the first polymeric portion having a solubility parameter S I, the second polymer portion having a solubility parameter S2, and (SI - S2) ² < 2, and one of the first and second polymer portions comprising a first additive.

[00160] Aspect 65B. A method, consisting of: by way of an additive manufacturing process, forming a second polymer portion in contact with a first polymer portion, the first polymeric portion having a solubility parameter S I, the second polymer portion having a solubility parameter S2, and (SI - S2) ² < 2, and one of the first and second polymer portions comprising a first additive.

[00161] Aspect 65C. A method, consisting essentially of: by way of an additive manufacturing process, forming a second polymer portion in contact with a first polymer portion, the first polymeric portion having a solubility parameter SI, the second polymer portion having a solubility parameter S2, and (SI - S2) ² < 2, and one of the first and second polymer portions comprising a first additive.

[00162] Aspect 66. The method of any of aspects 65A-65C. wherein the first polymer portion comprises at least one of an acrylonitrile styrene acrylate, a polycarbonate, a polylactic acid, a polycaprolactone, or any combination thereof. [00163] Aspect 67. The method of any of aspects 65A-66, wherein the second polymer portion comprises at least one of an acrylonitrile styrene acrylate, a polycarbonate, a polylactic acid, a polycaprolactone, or any combination thereof.

[00164] Aspect 68. The method of any of aspects 65A-67, wherein the first polymer portion additive is characterized as being in the class of a UV absorber, a UV stabilizer, a heat stabilizer, an antistatic agent, an anti-drip agent, a radiation stabilizer, a pigment, a dye, a filler, a fiber, a plasticizer, a lubricant, a mold release agent, a flame retardant, an antioxidant, or a combination thereof.

[00165] Aspect 69. The method of any of aspects 65A-68, wherein the second polymer portion comprises a second polymer portion additive.

[00166] Aspect 70. The method of aspect 69, wherein the second polymer additive is of the same class as the first polymer portion additive.

[00167] Aspect 71. The method of any of aspects 69-70. wherein the percentage, by weight, of the first polymer portion additive in the first polymer portion differs from the percentage, by weight, of the second polymer portion additive in the second polymer portion.

[00168] Aspect 72. The method of any of aspects 65A-71, wherein the additive manufacturing process comprises one or more of fused deposition modeling, material jetting, or selective laser sintering.

[00169] Aspect 73. The method of any of aspects 65A-72, wherein the first and second polymer portions comprise an acrylonitrile styrene acrylate, the first and second polymer portions comprise a polycarbonate, the first and second polymer portions comprise a polylactic acid, or the first and second polymer portions comprise a polycaprolactone.