Patent Description:
There are currently a limited number of ceramic-polymer composites with a high proportion of ceramic. Known ceramic-polymer composites typically contain significantly less than <NUM>% by volume of ceramic, and significantly more than <NUM>% by volume of polymer.

A first category of such ceramic-polymer composites relies on a thermoset approach in which a monomer is combined with the porous ceramic structure and cured to form a composite. But this approach generally requires undesirably-long curing times, and density of a final part is generally dependent on the size of pores in the ceramic and the viscosity of the resin.

A second category of such ceramic-polymer composites relies on thermoplastic polymers, which generally do not require time to cure and can instead be simply heated to melt and subsequently cooled to solidity the thermoplastic polymer, thereby enabling relatively faster processing. Ceramic fillers have been compounded with thermoplastics to achieve certain properties, including stiffness and strength. However, the ceramic filler content in such thermoplastic polymers is typically limited to significantly less than <NUM>% by volume due to limitations of conventional compounding technology. For example, in a traditional approach of this type, a ceramic filler is added to a polymer and the mixture is compounded in an extruder and palletized. Generally, the dispersion and distribution of the ceramic filler in the polymer matrix is highly dependent on the type of ceramic and polymer, other additives and coupling agents, rate of mixing, shear rate, temperature, and various other parameters. Due at least to these limitations, higher proportions of ceramics fillers e.g., greater than <NUM> % by volume) in a polymer matrix is challenging, and may for example damage the screws in an extruder (depending on the hardness of the ceramic) and degrade the polymer because of shear and heat.

A third category of such ceramic-polymer composites relies on the more-recently identified approach known as "cold sintering," various aspects of which may be described in U. Patent App. No. <CIT> and PCT Application Pub. (<NUM>) <CIT>, (<NUM>)No. <CIT>, (<NUM>) <CIT>, and (<NUM>) <CIT>. One drawback with cold sintering, however, is that not all ceramics can be effectively cold sintered. For example, certain structural ceramics like Aluminum Oxide, Zirconia, Titanium Oxide, and Silicon Carbide generally cannot be cold sintered. Additionally, the structures produced by cold sintering typically utilize ceramic as the matrix and polymer as the filler, which generally results in differing structural properties and differing suitability for various end-use applications.

A fourth category of such ceramic-polymer composites can involve dissolving an amorphous polymer in a solvent, and mixing ceramic particles into the polymer-solvent mixture. For example, a sprouted-bed granulation process can be used to create polymer-coated ceramic powders, such as described in <NPL>.

<CIT> discusses composite particles completely or partially coated in a precipitated polymer and methods of producing thereof.

Described herein are polymer-ceramic core-shell particles in which the polymer shell exhibits induced crystallinity, and powders and pellets of such core-shell particles. The invention provides a method of making such core-shell particles in powder form (as a ceramic-polymer composite powder). Also provided herein are methods of molding a part from a powder of such core-shell particles. Such core-shell particles comprise a core and a shell around the core, in which the shell comprises a polymer exhibiting induced crystallinity, and the core comprises a ceramic. The polymer is generally amorphous but exhibits induced crystallinity when formed into a shell of the present core-shell particles, and is selected from the group of polymers consisting of: polycarbonate (PC) copolymers, polyetherimide (PEI), polyetherimide (PEI) copolymers, polyphenylsulfone (PPSU), polyarylethersulfone (PAES), and polyether sulfones (PES). The induced crystallinity of the polymer shell is recognizable and characterized in that the polymer of the shell exhibits both a glass transition temperature (Tg) and a melt temperature (Tm), for example as determined via differential scanning calorimetry (DSC) described below. The ceramic is selected from the group of ceramics consisting of: Alumina (Al<NUM>O<NUM>), Ferric Oxide (Fe<NUM>O<NUM>), Iron (II, III) Oxide (Fe<NUM>O<NUM>), Zinc Oxide (ZnO), Zirconia (ZrO<NUM>), and Silica (SiO<NUM>). Such core-shell particles, and powders and pellets thereof, permit the molding of ceramic-composite molded parts with high ceramic content by conventional processes such as compression molding and injection molding.

The present methods of making a ceramic-polymer composite powder permit the formation of core-shell particles with relatively uniform coatings of the polymer shell material. More particularly, in the herein described core-shell particles (formed by the present methods), the shell can surround substantially all of the surface of the core, at least in configurations in which the polymer comprises at least <NUM>% by volume of the core-shell particles. Likewise, the herein described core-shell particles (formed by the present methods) facilitate the molding of ceramic-polymer composite parts with significantly less agglomeration of ceramic particles than prior compounding methods in which parts are molded from a mixture of separate ceramic particles and polymer particles. By way of example, and not to be limited by a particular theory, it is currently believed that the substantially uniform polymer coating formed on the ceramic core causes the polymer to resist separation from the ceramic during processing and molding, and thereby resist contact between (and agglomeration of) the ceramic cores. Further, the present methods of making the ceramic-polymer composite powders permit the formation of relatively fine, relatively consistent powders without the need for grinding or sieving. The present methods can also result in core-shell particles with less variation in size relative to the starting polymer powder which, in turn, leads to more uniform distribution of ceramic and polymer in molded part than has been possible with traditional compounding methods in which parts are molded from a mixture of separate ceramic particles and polymer particles. For example, as described in more detail below in Table 1B, the Dv90 of the PPS-Al<NUM>O<NUM> was about <NUM>% of the Dv90 of the raw PPS powder used in the described examples.

Ultimately, the present methods permit the formation of powders of polymer-ceramic core-shell particles with relatively large fractions of ceramic (e.g., greater than <NUM>% by volume, between <NUM>% and <NUM>% by volume, between <NUM>% and <NUM>% by volume, and/or the like). By way of further example, for ceramic:polymer ratios between <NUM>:<NUM> and <NUM>:<NUM> by volume, the ceramic particles can have a surface area of from <NUM> to <NUM><NUM>/g (e.g., from <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, or <NUM> to <NUM><NUM>/g); for ceramic:polymer ratios between <NUM>:<NUM> and <NUM>:<NUM> by volume, the ceramic particles can have a surface area of from <NUM> to <NUM><NUM>/g (e.g., from <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, or <NUM> to <NUM><NUM>/g,,); for ceramic:polymer ratios between <NUM>:<NUM> and <NUM>:<NUM> by volume, the ceramic particles can have a surface area of from <NUM> to <NUM><NUM>/g (e.g., from <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, or <NUM> to <NUM><NUM>/g,); and for ceramic:polymer ratios between <NUM>:<NUM> and <NUM>:<NUM> by volume, the ceramic particles can have a surface area of from <NUM> to <NUM><NUM>/g (e.g., from <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, <NUM> to <NUM><NUM>/g, or <NUM> to <NUM><NUM>/g).

By way of example, such polymer-ceramic core-shell particles with higher proportions of structural ceramic (i.e., Al<NUM>O<NUM> , ZnO, Fe<NUM>O<NUM> , Fe<NUM>O<NUM> , ZrO<NUM> , or SiO<NUM>) can be beneficial in structural components like gears, CE housings, protective shields, and the like because these types of applications typically benefit from properties such as wear resistance, hardness, scratch resistance, toughness, and stiffness. Additionally, the inclusion of ceramic particles in a polymer matrix can permit the adjustment and/or selection of properties like dielectric constant, dissipation factor, and RF transparency that can be beneficial for certain electronics applications.

Certain configurations of the herein described ceramic-polymer composite powders comprise: a plurality of core-shell particles, where: each of the core-shell particles comprises a core and a shell around the core; the core comprises a particle of a ceramic selected from the group of ceramics consisting of: Al<NUM>O<NUM> , Fe<NUM>O<NUM> , Fe<NUM>O<NUM> , ZnO, ZrO<NUM> , SiO<NUM> , and combinations of any two or more of these ceramics; the shell comprises a polymer selected from the group of polymers consisting of: polycarbonate (PC) copolymers, polyetherimide (PEI), polyetherimide (PEI) copolymers, polyphenylsulfone (PPSU), polyarylethersulfone (PAES), and polyether sulfones (PES); where the core-shell particles are in powder form. The core-shell particles can comprise between <NUM>% and <NUM>% by volume of the ceramic, and between <NUM>% and <NUM>% by volume of the polymer; and/or can have a Dv50 of from <NUM> nanometers (nm) to <NUM> micrometers (µm). Typically, substantially all of the polymer is not cross-linked.

Certain configurations of the herein described dense polymer-ceramic composite articles comprise: a polymer matrix and ceramic filler disposed in the polymer matrix; where the ceramic filler comprises particles of a ceramic selected from the group of ceramics consisting of: Al<NUM>O<NUM> , Fe<NUM>O<NUM>, Fe<NUM>O<NUM> , ZnO , ZrO<NUM> , SiO<NUM> , and combinations of any two or more of these ceramics; where the polymer matrix comprises a polymer selected from the group of polymers consisting of: polycarbonate (PC) copolymers, polyetherimide (PEI), polyetherimide (PEI) copolymers, polyphenylsulfone (PPSU), polyarylethersulfone (PAES), and polyether sulfones (PES); and where the Relative Density of the article is greater than <NUM>%. The ceramic filler can comprise between <NUM>% and <NUM>% by volume of the article, and the polymer matrix can comprise between <NUM>% and <NUM>% by volume of the article. Typically, the ceramic particles are substantially free of agglomeration.

The herein described ceramic-polymer composite materials can also be pelletized (converted to pellet form). Such pelletized material can comprise: a plurality of solid pellets each comprising a plurality of core-shell particles, where: each of the core-shell particles comprises a core and a shell around the core; the core comprises a particle of a ceramic selected from the group of ceramics consisting of: Al<NUM>O<NUM> , Fe<NUM>O<NUM> , Fe<NUM>O<NUM> , ZnO , ZrO<NUM> , SiO<NUM> , and combinations of any two or more of these ceramics; the shell comprises a polymer selected from the group of polymers consisting of: polycarbonate (PC) copolymers, polyetherimide (PEI), polyetherimide (PEI) copolymers, polyphenylsulfone (PPSU), polyarylethersulfone (PAES), and polyether sulfones (PES); and the shells of adjacent core-shell particles are joined to resist separation of the adjacent core-shell particles and deformation of a respective pellet. In such pellets, the core-shell particles can comprise between <NUM>% and <NUM>% by volume of the ceramic, and between <NUM>% and <NUM>% by volume of the polymer. Typically, substantially all of the polymer is not cross-linked.

The invention provides a method of forming a ceramic-polymer composite powder, wherein the method comprises: mixing a polymer, solvent, and particles of a ceramic; dissolving at least partially the polymer in the solvent by superheating the mixture to a first temperature above the normal boiling point of the solvent and while maintaining the mixture at a first pressure at which the solvent remains substantially liquid; agitating the superheated mixture for a period of minutes while maintaining the mixture at or above the first temperature and at or above the first pressure; and cooling the mixture to or below a second temperature below the normal boiling point of the solvent to cause the polymer to precipitate on the particles of the ceramic and thereby form a plurality of core-shell particles each comprising a core and a shell around the core, where the core comprises a particle of the ceramic and the shell comprises the polymer. The polymer is selected from the group of polymers consisting of: polycarbonate (PC) copolymers, polyetherimide (PEI), polyetherimide (PEI) copolymers, polyphenylsulfone (PPSU), polyarylethersulfone (PAES), and polyether sulfones (PES); and the ceramic is selected from the group of ceramics consisting of: Al<NUM>O<NUM> , Fe<NUM>O<NUM> , Fe<NUM>O<NUM> , ZnO , ZrO<NUM> , SiO<NUM> , and combinations of any two or more of these ceramics.

In some instances of the method, the mixing step comprises: mixing the solvent and the particles of the ceramic; agitating the mixture of the solvent and the particles of the ceramic to de-agglomerate the particles of the ceramic; mixing the polymer into the agitated mixture of the solvent and the particles of the ceramic. In some instances, the method comprises one or more steps selected from the group of steps consisting of: agitating the mixture during the cooling step; washing the core-shell particles after the cooling step; and drying the core-shell particles at a temperature above the normal boiling point of the solvent, optionally at a second pressure below ambient pressure. In some instances, the solvent comprises a solvent selected from the group of solvents consisting of: Methyl Ethyl Ketone (MEK), N-Methyl-<NUM>-pyrrolidone (NMP), orthodichlorobenzene (ODCB), and Xylene.

Also described herein are methods of molding a part from the herein described core-shell particles, the method comprising: subjecting a powder of one of the herein described polymer-ceramic core-shell particles to a first pressure while the powder is at or above a first temperature that exceeds a melting temperature of the polymer; where the powder substantially fills a working portion of a cavity of a mold.

The terms "a" and "an" are defined as one or more unless this disclosure explicitly requires otherwise. The terms "substantially" and "about" are each defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially <NUM> degrees includes <NUM> degrees), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the term "substantially" or "about" may be substituted with "within [a percentage] of" what is specified, where the percentage includes. <NUM>, <NUM>, <NUM>, and <NUM> percent.

The phrase "and/or" means and or or. To illustrate, A, B, and/or C includes: A alone, B alone, C alone, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C. In other words, "and/or" operates as an inclusive or. The phrase "at least one of A and B" has the same meaning as "A, B, or A and B.

The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), and "include" (and any form of include, such as "includes" and "including") are open-ended linking verbs. As a result, an apparatus that "comprises," "has," or "includes" one or more elements possesses those one or more elements, but is not limited to possessing only those one or more elements. Likewise, a method that "comprises," "has," or "includes" one or more steps possesses those one or more steps, but is not limited to possessing only those one or more steps.

As used herein, a "size" or "diameter" of a particle refers to its equivalent diameter-referred to herein as its diameter-if the particle is modelled as a sphere. A sphere that models a particle can be, for example, a sphere that would have or produce a value measured for the particle, such as the particle's mass and/or volume, light scattered by the particle, or the like. Particles of the present dispersions can, but need not, be spherical.

Any embodiment of any of the apparatuses, systems, and methods can consist of or consist essentially of - rather than comprise/have/include - any of the described steps, elements, and/or features. Thus, in any of the claims, the term "consisting of" or "consisting essentially of" can be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open-ended linking verb.

The feature or features of one embodiment may be applied to other embodiments, even though not described or illustrated, unless expressly prohibited by this disclosure or the nature of the embodiments.

Some details associated with the embodiments are described above and others are described below.

The following drawings illustrate by way of example and not limitation. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which that structure appears. Identical reference numbers do not necessarily indicate an identical structure. Rather, the same reference number may be used to indicate a similar feature or a feature with similar functionality, as may non-identical reference numbers.

Referring now to the drawings, and more particularly to <FIG>, a schematic illustration is shown of one of the herein described core-shell particles <NUM> comprising a core <NUM> and a shell <NUM> around the core. In the illustrated configurations, for example, core <NUM> comprises a single particle of Alumina (Al<NUM>O<NUM>), Ferric Oxide (Fe<NUM>O<NUM>), Iron (II, III) Oxide (Fe<NUM>O<NUM>), Zinc Oxide (ZnO), Zirconia (ZrO<NUM>), or Silica (SiO<NUM>), and may have a spherical, elongated (e.g., cylindrical), irregular, or otherwise fanciful shape as shown. In other configurations, the core may comprise an agglomeration of two or more particles, and/or may have a substantially spherical shape. Shell <NUM> comprises a polymer selected from the group of polymers consisting of: polycarbonate (PC) copolymers, polyetherimide (PEI), polyetherimide (PEI) copolymers, polyphenylsulfone (PPSU), polyarylethersulfone (PAES), and polyether sulfones (PES). In the illustrated configuration, shell <NUM> covers or surrounds substantially all of core <NUM>. In other configurations, the shell need not cover or surround all of the core (e.g., may cover a majority of the core). As described in more detail below, the present methods permit the formation of a polymer shell (e.g., <NUM>) that is not cross-linked and, for certain polymers, that exhibits induced crystallinity.

In the herein described core-shell particles, the core (e.g., <NUM>) can have a particle size (e.g., diameter or minimum transverse dimension) of from <NUM> nanometers (nm) to <NUM> micrometers (µm). For example, the cores in a ceramic powder used to form core-shell particles in the present methods can have a Dv90 or Dv50 of between <NUM> and <NUM> (e.g., from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>, from <NUM> to <NUM>).

The herein described powders comprise a plurality of particles <NUM>, for example in a powder form. For example, a powder may be characterized by a polymer-solvent content (a solvent in which the polymer is dissolvable) of less than <NUM>,<NUM> parts per million (ppm) (e.g., less than <NUM>,<NUM> ppm, less than <NUM>,<NUM> ppm). However, in some configurations, the powder may mixed with and/or suspended in a liquid that is not a polymer-solvent (a liquid in which the polymer will not dissolve), such as water. In such configurations, the liquid may resist and/or prevent particles from becoming airborne or breathable, such as for transportation and handling of finer powders.

In some configurations of such powders, the core-shell particles comprise between <NUM>% and <NUM>% by volume of the ceramic (e.g., <NUM>% and <NUM>% by volume of the ceramic).

<FIG> is a schematic illustration of the internal structure of a part molded from a dry powder of the herein described core-shell particles <NUM>. As shown, the polymer shells <NUM> of adjacent particles merge together to fill interstices between and bond the particles together. As shown, the relatively higher proportion (e.g., <NUM>% to <NUM>% by volume) of ceramic in the powder means that a correspondingly higher proportion of the molded part is also ceramic. Further, the core-shell structure of the particles prior to molding results in more-uniform distribution of polymer within the matrix of the molded part. By way of example, the herein described core-shell particles, in which the ceramic particles are substantially free of agglomeration and/or substantially all of the ceramic particles are each substantially surrounded by polymer, enable the molding of parts that are also substantially free of agglomeration and/or in which substantially all of the ceramic particles is separated by a layer of polymer from adjacent ceramic polymer particles.

The herein described powders can also be pelletized or joined into a pellet form in which the shells of adjacent core-shell particles are joined to resist separation of the adjacent core-shell particles and deformation of a respective pellet. For example, the herein described powders may be subjected to elevated temperatures and pressures in an extruder. Such temperatures may be at or near the glass transition temperature (Tg) or the melting temperature (Tm) of the polymer in the core-shell particles to render the polymer tacky but not liquefied, and such pressures (e.g., during extrusion) may be elevated relative to ambient, such that shells of adjacent core-shell particles join sufficiently to resist separation but no so much that the independent boundaries/identities of adjacent shells are lost. In such configurations, the pellet form may facilitate transportation of the core-shell particles (e.g., for distribution). Such pelletization can be achieved by any of various methods and processes that are known in the art, such as, for example, via a screw extruder.

Polycarbonate (PC) refers generally to a group of thermoplastic polymers containing carbonate groups. PCs used in engineering are strong, tough materials, and some grades are optically transparent. PCs are typically easily worked, molded, and thermoformed, and therefore are used in various applications. The present configurations and implementations utilize a polycarbonate copolymer or interpolymer rather than a homopolymer. Polycarbonate copolymers can include copolycarbonates comprising two or more different types of carbonate units, for example units derived from BPA and PPPBP (commercially available under the trade name XHT or CXT from SABIC); BPA and DMBPC (commercially available under the trade name DMX from SABIC); or BPA and isophorone bisphenol (commercially available under the trade name APEC from Bayer). The polycarbonate copolymers can further comprise non-carbonate repeating units, for example repeating ester units (polyester-carbonates), such as those comprising resorcinol isophthalate and terephthalate units and bisphenol A carbonate units, such as those commercially available under the trade name LEXAN SLX from SABIC; bisphenol A carbonate units and isophthalate-terephthalate-bisphenol A ester units, also commonly referred to as poly(carbonate-ester)s (PCE) or poly(phthalate-carbonate)s (PPC), depending on the relative ratio of carbonate units and ester units; or bisphenol A carbonate units and C<NUM>-<NUM> dicarboxy ester units such as sebacic ester units (commercially available under the trade name HFD from SABIC). Other polycarbonate copolymers can comprise repeating siloxane units (polycarbonate-siloxanes), for example those comprising bisphenol A carbonate units and siloxane units (e.g., blocks containing <NUM> to <NUM> dimethylsiloxane units), such as those commercially available under the trade name EXL from SABIC; or both ester units and siloxane units (polycarbonate-ester-siloxanes), for example those comprising bisphenol A carbonate units, isophthalate-terephthalate-bisphenol A ester units, and siloxane units (e.g., blocks containing <NUM> to <NUM> dimethylsiloxane units), such as those commercially available under the trade name FST from SABIC. Combinations of any of the above materials can be used.

Polyetherimide (PEI) is an amorphous, amber-to-transparent thermoplastic with characteristics similar in some respects to polyether ether ketone (PEEK). Relative to PEEK, PEI may be lower in impact strength and usable temperature. Examples of PEI are available from SABIC Innovative Plastics under the trade names ULTEM, SILEM, and EXTEM.

The polyetherimide can be selected from polyetherimide homopolymers, e.g., polyetherimides, polyetherimide co-polymers, e.g., polyetherimide sulfones, and combinations thereof. Polyetherimides include, but are not limited to, known polymers, such as those sold by SABIC Innovative Plastics under the Ultem*, Extern*, and Siltem* brands (Trademark of SABIC Innovative Plastics IP B.

Polyarylethersulfones or poly(aryl ether sulfone)s (PAES) are typically linear, amorphous, injection moldable polymers possessing a number of desirable features such as excellent high temperature resistance, good electrical properties, and toughness. Due to their excellent properties, the poly(aryl ether sulfone)s can be used to manufacture a variety of useful articles such as molded articles, films, sheets, and fibers.

Polyphenylsulfone (PPSU) is an amorphous, heat-resistant and transparent high-performance thermoplastic. PPSU is generally known in the art as having high toughness and flexural and tensile strength, excellent hydrolytic stability, and resistance to chemicals and heat.

The below-described PPSU examples utilized amorphous polyphenylsulfone, CAS Reg. No. <NUM>-<NUM>-<NUM>, having a weight average molecular weight of <NUM>,<NUM> grams/mole and a number average molecular weight of <NUM>,<NUM> grams/mole (determined by gel permeation chromatography using a polystyrene standard); having a hydroxyl group content less than <NUM> parts per million by weight; and obtained in pellet form as RADEL* R5100-<NUM> polyphenylsulfone. RADEL is a trademark of Solvay, Inc.

Polyethersulfones (PES) are typically linear, amorphous, injection moldable polymers possessing a number of desirable features such as excellent high temperature resistance, good electrical properties and toughness. Due to their excellent properties, the polyethersulfones can be used to manufacture a variety of useful articles such as molded articles, films, sheets and fibers. PES offers high chemical and solvent resistance and is particularly useful for manufacturing articles that are exposed to solvents or chemical agents at elevated temperatures and for extended times. Thus, PES finds application in articles such as medical trays, which are subjected to repeated and rigorous sterilization procedures.

Referring now to <FIG> and <FIG>, <FIG> depicts a flowchart <NUM> of one example of a method of making a powder of the herein described core-shell particles (e.g. <NUM>), and <FIG> depicts a schematic illustration of stirring reactor <NUM> of a type (e.g., a PARR™ reactor) that can be used to make a powder of the herein described core-shell particles.

First mixing the ceramic particles with the solvent can have certain benefits, for example, in reducing the agglomerating of ceramic particles. This benefit can be realized whether beginning with ceramic particles that are not agglomerated in their powder form, or with ceramic particles that are agglomerated in their powder form. For example, the Al<NUM>O<NUM> powder (CAS <NUM>-<NUM>-<NUM>) used in the below-described examples was obtained from Alfa Aesar and, in its raw form prior to usage in the present methods, comprised spherical hollow particles with an average particle size of from <NUM> to <NUM> and surface area of from <NUM> to <NUM><NUM>/g. Mixing these hollow particles with solvent prior to adding polymer caused the hollow particles to break down into their smaller, solid particles components, which solid particles had an average particle size of <NUM> or smaller, while also resisting re-agglomeration of the solid particles during the subsequent mixing, dissolution, and precipitation of the polymer on the solid ceramic particles.

At a step <NUM>, polymer, solvent, and particles of ceramic are mixed together. The polymer, solvent, and ceramic may be mixed at the same time in a single vessel, or may be mixed sequentially. For example, the ceramic particles may first be mixed into a solvent (e.g., in a first vessel, such as a homogenizer), and the polymer may subsequently be mixed into the solvent-ceramic mixture (e.g., in the first vessel or in a second vessel, such as a shell or container <NUM> of stirring reactor <NUM>). The solvent may comprise any solvent in which the polymer will dissolve under superheated conditions, as described below. Examples of solvents that may be utilized with certain of the present polymers include Methyl Ethyl Ketone (MEK), N-Methyl-<NUM>-pyrrolidone (NMP), orthodichlorobenzene (ODCB), dicloromethane, and Xylene. By way of example, ODCB may be used with PEI and certain PEI copolymers, ODCB may be used with PPSU, dicloromethane may be used with PES, and Xylene may be used with certain PC copolymers. Other solvents that may be utilized in the present methods include those in which a selected polymer is Freely Soluble or Soluble at elevated temperatures (e.g., above <NUM>, above <NUM>, about <NUM>, and/or above <NUM>), and Slightly Soluble or Sparingly Soluble at lower temperatures (e.g., below <NUM>, such as at ambient temperatures). As used herein, Freely Soluble requires <NUM> to <NUM> of solvent to dissolve <NUM> gram (g) of the polymer, Soluble requires <NUM> to <NUM> of solvent to dissolve <NUM> gram (g) of the polymer; Slightly Soluble requires <NUM> to <NUM> of solvent to dissolve <NUM> gram (g) of the polymer; Sparingly Soluble requires <NUM> to <NUM> of solvent to dissolve <NUM> gram (g) of the polymer.

At a step <NUM>, the mixture of polymer, ceramic, and solvent is superheated (e.g., via a heating element <NUM> of reactor <NUM>) to at least partially (e.g., fully) dissolve the polymer in the solvent. In particular, the mixture is heated to a first temperature that exceeds the normal boiling point of the solvent (and exceeds the glass transition temperature of an amorphous polymer), under a first pressure at which the solvent remains liquid. For example, when using ODCB as the solvent, the mixture can be heated to <NUM> under a pressure of up to <NUM> pounds per square inch (psi) (e.g., <NUM> psi). By way of additional sample, when using Xylene as the solvent, the mixture can be heated to <NUM> under a pressure of up to <NUM> pounds per square inch (psi) (e.g., <NUM> psi). When using other solvents, the pressure may be kept at a different level (e.g., <NUM> psi).

At a step <NUM>, which may be partially or entirely simultaneous with step <NUM>, the mixture is agitated (e.g., via impeller <NUM> of reactor <NUM>) for a period of minutes (e.g., equal to or greater than <NUM> minute, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, or more) while the temperature of the mixture is substantially maintained at or above the first temperature, and the pressure to which the mixture is subjected is substantially maintained at or above the first pressure. In particular, the temperature and pressure are maintained during agitation to keep the mixture in a superheated state.

At a step <NUM>, the mixture is cooled to or below a second temperature that is below the normal boiling point of the solvent to cause the polymer to precipitate on the particles of the ceramic and thereby form a plurality of the herein described core-shell particles (e.g., <NUM>). For example, when using ODCB as the solvent, the mixture may be cooled to less than <NUM>, less than <NUM>, and/or to <NUM>. By way of further example, when using Xylene as the solvent, the mixture may be cooled to less than <NUM>, less than <NUM>, and/or to <NUM>. Optionally, the mixture may continue to be agitated during this cooling step to resist agglomeration of the core-shell particles.

At an optional step <NUM>, the formed core-shell particles may be washed or rinsed, either with the same solvent added in step <NUM> (e.g., ODCB or Xylene) or with a different solvent (e. g, Methanol or MeOH). For example, the wet solids cake can be removed from the vessel (e.g., shell or container <NUM> of reactor <NUM>) and placed in a filter for rinsing.

At a step <NUM>, the solids cake is dried to form a dry powder of the core-shell particles (e.g., <NUM>), for example, at a temperature above the normal boiling point of the solvent added in step <NUM> and/or of the solvent used to wash/rinse the solids cake at optional step <NUM>, optionally at a second pressure below ambient pressure (i.e., under vacuum). For example, when ODCB (normal boiling point of ~<NUM>) is added at step <NUM> and MeOH (normal boiling point of ~<NUM>) is used in step <NUM>, the solids cake can be dried under vacuum at a temperature of <NUM> for a period of time (e.g., <NUM> hours, <NUM>, hours, <NUM> hours, <NUM> hours, <NUM> hours, or more). By way of further example, when Xylene (normal boiling point of ~<NUM>) is added at step <NUM> and MeOH (normal boiling point of ~<NUM>) is used in step <NUM>, the solids cake can be dried under vacuum at a temperature of <NUM> for a period of time (e.g., <NUM> hours, <NUM>, hours, <NUM> hours, <NUM> hours, <NUM> hours, or more).

Prior to mixing the polymer with the solvent and ceramic at step <NUM>, the polymer is amorphous. However, after the cooling at step <NUM> and/or after drying at step <NUM>, the polymer of the shell exhibits induced crystallinity. The induced crystallinity of the polymer shell is recognizable and characterized in that the polymer of the shell exhibits both a glass transition temperature (Tg) and a melt temperature (Tm), for example as determined via differential scanning calorimetry (DSC) described below.

Also described herein are methods of molding parts from polymer-ceramic core-shell particle powders. Referring now to <FIG> depicts a flowchart <NUM> of one example of a method of molding a part from a powder of the herein described core-shell particles, and <FIG> depicts a schematic illustration <NUM> of a compression mold for molding a part.

At a step <NUM>, a working portion of a cavity <NUM> of a mold <NUM> is filled with a powder <NUM> of the herein described core-shell particles (e.g., <NUM>).

At a step <NUM>, the powder (<NUM>) is heated to at or above a first temperature (e.g., via a heating jacket <NUM>) that exceeds (e.g., by at least <NUM>, at least <NUM>, at least <NUM>, or more) a melting temperature (Tm) of the polymer. For example, when the Tg of a particular PEI copolymer is ~<NUM>, the first temperature can be <NUM>. By way of further example, when the Tg of a particular PC copolymer is ~<NUM>, the first temperature can be <NUM>.

At a step <NUM>, which may be partially or entirely simultaneous with step <NUM>, the powder is subjected to a first pressure (e.g., <NUM> Megapascals (MPa)) in the mold while the powder (e. g, and the mold) is held at or above the first temperature. The pressure may be maintained for a period of minutes (e.g., equal to or greater than <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, <NUM> minutes, or more). In some implementations, the conditions (temperature, pressure, and/the like) and period of time for which the conditions are maintained are sufficient to result in a molded part with a relative density of greater than <NUM>%.

Materials: <NUM> grams (g) Zinc Oxide (ZnO), <NUM> PEI copolymer pellets (ULTEM CRS5001, SABIC Innovative Plastics IP B. ), <NUM> ODCB (split into <NUM> and <NUM> portions). Relative amounts of Zinc Oxide and PEI copolymer resulted in Zinc Oxide being about <NUM>% by volume of the formed core-shell particles.

Procedure: The Zinc Oxide was homogenized in the <NUM> portion of the ODCB in a <NUM> beaker using an IKA homogenizer (available from IKA Works, Inc. (Wilmington, NC USA)) for <NUM> minutes at <NUM>,<NUM> revolutions per minute (rpm). A small amount of the <NUM> portion of the ODCB was then used to rinse the homogenizer head to remove residual Zinc Oxide from the homogenizer head. The Zinc Oxide and ODCB mixture, and the PEI copolymer, were then added to a <NUM> PARR™reactor shell/container with agitator. Some of the remainder of the <NUM> portion of the ODCB was used to rinse the beaker, with all of the ODCB then being added to the PARR™reactor shell. The PARR™reactor shell was then attached to the PARR™reactor unit and the reactor controller was powered on. An line from a nitrogen (N<NUM>) source was then attached to the head-space port of the PARR™reactor shell, and the headspace in the shell purged several times with N<NUM>. During the purging process, the pressure in the reactor shell was observed to ensure a tight seal. In particular, it was known that the N<NUM> in a sealed reactor shell would typically reach <NUM>-<NUM> psi. As such, once the N<NUM> was added to the headspace, the N<NUM> source was turned off and all of valves on the PARR™ reactor were closed. When the pressure remained substantially constant after about <NUM> seconds (s), the pressure was released and the headspace purged with N<NUM> two or three total times. If instead the pressure decreased, the pressure was released, the unit tightened again, and the process repeated until the pressure remained constant and the headspace could be thereafter purged the two or three total times. After the headspace was purged, the thermocouple was inserted into the temperature port on the reactor shell, and the cooling water line for the agitator was opened or turned on. The locking ring was then added around the point at which the shell attached to the rest of the PARR™ reactor unit and tightened as much as possible by hand. The heater was then aligned with and secured around the reactor shell.

On the reactor controller, the primary temperature was then set to <NUM>, the high limit pressure was set to <NUM> psi, the high limit temperature was set to <NUM>. The heater was then set to Setting II (highest heat setting) and the agitator/impellor turned on and set to ~<NUM> rpm. Once the temperature reached ~<NUM>, the heater was turned down to Setting I to allow for the maintenance of a more consistent temperature at <NUM> (to avoid the temperature fluctuating higher or lower than <NUM>). Once the thermocouple indicated the mixture in the reactor shell had reached <NUM>, the reactor was held at that temperature for <NUM> minutes (min) while agitation continued. Reaction pressure at this temperature was about <NUM> psi or less, but in other implementations could be managed to be as high as <NUM> psi. After <NUM> minutes, the heater was turned off and the mixture allowed to cool to a temperature below <NUM> (time permitting, the mixture could be allowed to cool to <NUM>) to ensure that all PEI copolymer had precipitated. Once below <NUM>, the pressure was typically at about <NUM> psi. The pressure release valve was then slowly turned to lower the pressure to ~<NUM> psi. Once the pressure was relieved, the agitator was turned off, the reactor controller was turned off, and the cooling water line was turned off. The heater was then removed and the shell disengaged from the rest of the PARR™reactor unit. The mixture in the reactor shell was then poured into a small beaker, and about an additional <NUM> milliliters (mL) of ODCB was used to rinse residual material from the interior of the reactor shell for transfer to the beaker. The material in the beaker was then poured into a Buchner funnel and filter flask setup with a Whatman GF/F glass microfibre filter paper. The filtered wet cake was then rinsed with about <NUM> of Methanol (MeOH), and placed into an aluminum pan and dried under vacuum at <NUM> overnight. <FIG> depicts Zinc Oxide particles, and <FIG> depicts the PEI copolymer-Zinc Oxide core-shell particles. Certain properties of the resulting dry powder of PEI copolymer-ZnO core-shell particles were then measured and are included in Tables <NUM> and <NUM> below.

Materials: <NUM> grams (g) Ferric Oxide (Fe<NUM>O<NUM>), <NUM> PEI copolymer pellets (CRS5001), <NUM> ODCB (split into <NUM> and <NUM> portions). Relative amounts of Iron Oxide and PEI copolymer resulted in Iron Oxide being about <NUM>% by volume of the formed core-shell particles.

Procedure: The procedure for this Example <NUM> was substantially the same as that described above for Example <NUM>, with the exception that Ferric Oxide (Fe<NUM>O<NUM>) was used in place of Zinc Oxide (ZnO). Certain properties of the resulting dry powder of PEI copolymer-Fe<NUM>O<NUM> core-shell particles were then measured and are included in Table <NUM> below.

Materials: <NUM> grams (g) Silica (SiO<NUM>), <NUM> PEI copolymer (CRS5001), <NUM> ODCB (split into <NUM> and <NUM> portions). Relative amounts of Silica and PEI copolymer resulted in Silica being about <NUM>% by volume of the formed core-shell particles.

Procedure: The procedure for this Example <NUM> was substantially the same as that described above for Example <NUM>, with the exception that Silica (SiO<NUM>) was used in place of Zinc Oxide (ZnO). Certain properties of the resulting dry powder of PEI copolymer-SiO<NUM> core-shell particles were then measured and are included in Table <NUM> below.

Materials: <NUM> grams (g) Zirconia (ZrO<NUM>), <NUM> polycarbonate (PC) copolymer (LEXAN EXL1463T, SABIC Innovative Plastics IP B. ), <NUM> Xylene (split into <NUM> and <NUM> portions). Relative amounts of Zirconia and PC copolymer resulted in Zirconia being about <NUM>% by volume of the formed core-shell particles.

Procedure: The Zirconia was homogenized in the <NUM> portion of the ODCB in a <NUM> beaker using an IKA homogenizer (available from IKA Works, Inc. (Wilmington, NC USA)) for <NUM> minutes at <NUM>,<NUM> revolutions per minute (rpm). A small amount of the <NUM> portion of the Xylene was then used to rinse the homogenizer head to remove residual Zirconia from the homogenizer head. The Zirconia and Xylene mixture, and the PC copolymer, were then added to a <NUM> PARR™reactor shell/container with agitator. Some of the remainder of the <NUM> portion of the Xylene was used to rinse the beaker, with all of the Xylene then being added to the PARR™reactor shell. The PARR™reactor shell was then attached to the PARR™reactor unit and the reactor controller was powered on. An line from a nitrogen (N<NUM>) source was then attached to the head-space port of the PARR™ reactor shell, and the headspace in the shell purged several times with N<NUM>. During the purging process, the pressure in the reactor shell was observed to ensure a tight seal. In particular, it was known that the N<NUM> in a sealed reactor shell would typically reach <NUM>-<NUM> psi. As such, once the N<NUM> was added to the headspace, the N<NUM> source was turned off and all of valves on the PARR™reactor were closed. When the pressure remained substantially constant after about <NUM> seconds (s), the pressure was released and the headspace purged with N<NUM> two or three total times. If instead the pressure decreased, the pressure was released, the unit tightened again, and the process repeated until the pressure remained constant and the headspace could be thereafter purged the two or three total times. After the headspace was purged, the thermocouple was inserted into the temperature port on the reactor shell, and the cooling water line for the agitator was opened or turned on. The locking ring was then added around the point at which the shell attached to the rest of the PARR™ reactor unit and tightened as much as possible by hand. The heater was then aligned with and secured around the reactor shell.

On the reactor controller, the primary temperature was then set to <NUM>, the high limit pressure was set to <NUM> psi, the high limit temperature was set to <NUM>. The heater was then set to Setting II (highest heat setting) and the agitator/impellor turned on and set to ~<NUM> rpm. Once the temperature reached ~<NUM>, the heater was turned down to Setting I to allow for the maintenance of a more consistent temperature at <NUM> (to avoid the temperature fluctuating higher or lower than <NUM>). Once the thermocouple indicated the mixture in the reactor shell had reached <NUM>, the reactor was held at that temperature for <NUM> minutes (min) while agitation continued. Reaction pressure at this temperature was about <NUM> psi or less, but in other implementations could be managed to be as high as <NUM> psi. After <NUM> minutes, the heater was turned off and the mixture allowed to cool to a temperature below <NUM> (time permitting, the mixture could be allowed to cool to <NUM>) to ensure that all PC copolymer had precipitated. Once below <NUM>, the pressure was typically at about <NUM> psi. The pressure release valve was then slowly turned to lower the pressure to ~<NUM> psi. Once the pressure was relieved, the agitator was turned off, the reactor controller was turned off, and the cooling water line was turned off. The heater was then removed and the shell disengaged from the rest of the PARR™ reactor unit. The mixture in the reactor shell was then poured into a small beaker, and about an additional <NUM> milliliters (mL) of Xylene was used to rinse residual material from the interior of the reactor shell for transfer to the beaker. The material in the beaker was then poured into a Buchner funnel and filter flask setup with a Whatman GF/F glass microfibre filter paper. The filtered wet cake was then rinsed with about <NUM> of Methanol (MeOH), and placed into an aluminum pan and dried under vacuum at <NUM> overnight. Certain properties of the resulting dry powder of PEI copolymer-ZnO core-shell particles were then measured and are included in Table <NUM> below.

Materials: <NUM> of a dry powder of CRS5001-ZnO core-shell particles as produced in Example <NUM> described above.

Procedure: <NUM> of the powder was measured into an aluminum pan. Using a paper funnel, the powder was then poured into a circular cylindrical die of <NUM> millimeter (mm) internal diameter. The powder was then lightly compacted in the die using a rod, and a heating jacket was mounted around the die. The die was then heated to a first temperature of <NUM>, and maintained at the first temperature for five (<NUM>) minutes. A hydraulic press was then used to apply to the powder a pressure of <NUM> tons or <NUM> MPa. The mold was then held at the first temperature, with the powder under pressure, for a period of thirty (<NUM>) minutes, after which the heater was turned off and the die allowed to cool while the pressure was maintained. After <NUM> minutes, the PEI copolymer-Zinc Oxide composite pellet was removed from the die, and the pellet weighed and its dimensions measured to calculate relative density. <FIG> depicts the microstructure of the compressed pellet, and certain characteristics of the pellets are included in Table <NUM> below.

Materials: <NUM> grams (g) Alumina (Al<NUM>O<NUM>), <NUM> PPSU, <NUM> ODCB (split into <NUM> and <NUM> portions). Relative amounts of Alumina and PPSU resulted in Alumina being about <NUM>% by volume of the formed core-shell particles.

Procedure: The procedure for this Example <NUM> was substantially the same as that described above for Example <NUM>, with the exception that PPSU was used in place of PEI copolymer, the agitator/impellor was set to <NUM> rpm instead of ~<NUM> rpm, the reactor was held at temperature for <NUM> minutes instead of <NUM> minutes, the mixture was allowed to cool to <NUM> to ensure full precipitation instead of <NUM>, and the core-shell particles were dried at <NUM> instead of <NUM>. <FIG> depicts Alumina particles, and <FIG> depicts the PPSU-Alumina core-shell particles. Certain properties of the resulting dry powder of PPSU-Al<NUM>O<NUM> core-shell particles were then measured and are included in Tables <NUM> and <NUM> below.

Materials: <NUM> grams (g) Alumina (Al<NUM>O<NUM>), <NUM> PPSU, <NUM> ODCB(split into <NUM> and <NUM> portions). Relative amounts of Alumina and PPSU resulted in Alumina being about <NUM>% by volume of the formed core-shell particles. The PPSU was Radel® R5100 from Solvay, and the Alumina was MARTOXID® RN-<NUM> from HUBER Engineered Materials.

Procedure: The procedure for this Example <NUM> was substantially the same as that described above for Example <NUM>, with the exception that PPSU was used in place of PEI copolymer, the primary temperature was set to <NUM> instead of <NUM>, the mixture was allowed to cool to <NUM> to ensure full precipitation instead of <NUM>, and the core-shell particles were dried at <NUM> instead of <NUM>. <FIG> depicts the Alumina particles, and <FIG> depicts the PPSU-Alumina core-shell particles. Certain properties of the resulting dry powder of these PPSU-Al<NUM>O<NUM> core-shell particles were then measured and are included in Tables <NUM> and <NUM> below.

Materials: <NUM> of a dry powder of PPSU-Al<NUM>O<NUM> core-shell particles as produced in Example <NUM> described above.

Procedure: The procedure for this Example <NUM> was substantially the same as that described above for Example <NUM>, with the exceptions that PPSU-Al<NUM>O<NUM> core-shell particles were used instead of PEI copolymer-ZnO core-shell particles, and the die was heated to a first temperature of <NUM> instead of <NUM>. <FIG> depicts the microstructure of the compressed pellet, and certain characteristics of the pellets are included in Tables <NUM> and <NUM> below.

Procedure: The procedure for this Example <NUM> was substantially the same as that described above for Example <NUM>, with the exception that a <NUM> die was used instead of a <NUM> die. Certain properties of the resulting PPSU-Alumina pellet were then measured and are included in Table <NUM> below.

As explained above for Examples <NUM>-<NUM> and <NUM>-<NUM>, various combinations of powders with core-shell particles were produced, and certain processing parameters and properties of the powders are summarized in Table <NUM>. As explained above for Examples <NUM>-<NUM> and <NUM>-<NUM>, the superheat-cool powder-production process was carried out in a PARR™ reactor with reaction pressures less than or equal to <NUM> psi. With the exception of respective PEI copolymer (CRS5001) and PC copolymer (EXL1463T) reference powders, volume percent of ceramic or inorganic particles were kept constant at <NUM>% for comparison purpose. The CRS5001 reference powder, designated in Table <NUM> as "Example <NUM>-A" was made via a process similar to that described above for Example <NUM>, with the exception that ceramic particles were not included in the mixture, CRS5001 particles were included at <NUM>% by volume of the ODCB solvent, agitation proceeded at ~<NUM> rpm instead of ~<NUM> rpm, and it was not necessary to maintain the <NUM> temperature for <NUM> minutes to facilitate precipitation on ceramic particles. The EXL1463T reference powder, designated in Table <NUM> as "Example <NUM>-B" was made via a process similar to that described above for Example <NUM>, with the exception that ceramic particles were not included in the mixture, EXL1463T particles were included at <NUM>% by volume of the Xylene solvent, agitation proceeded at ~<NUM> rpm instead of ~<NUM> rpm, and it was not necessary to maintain the <NUM> temperature for <NUM> minutes to facilitate precipitation on ceramic particles.

Particle size values of the powders were measured with a commercial particle size analyzer (available from Malvern Panalytical Ltd. in Malvern, UK).

Morphology of the particles was also investigated using scanning electron microscopy. For example, <FIG> shows uncoated Zinc Oxide particles; <FIG> shows PEI copolymer (CRS5001)-coated Zinc Oxide particles; and <FIG> shows PEI copolymer (CRS5001)-Zinc Oxide core-shell particles compression molded into a part. PEI copolymer coating on the ceramic particles is evident on the core-shell powder in <FIG>. A thin layer of PEI copolymer is also evident between the ceramic grains in <FIG>.

Thermogravimetric analysis (TGA) and molecular weight (measured via GPC) properties for the core-shell powder of Example <NUM>, describe above, are summarized in Table <NUM>. In addition, certain TGA and molecular weight properties were determined for the components of the respective core-shell powders, namely Zinc Oxide powder (Example 1A) and PEI copolymer (CRS5001) powder (Example 1B, respectively). The density and molecular weight of the respective powders is given as comparative reference. No apparent degradation in molecular weight of the polymer was observed as a result of the present superheating-cooling methods of making the present core-shell particles.

TGA and molecular weight (measured via GPC) results on compression molded parts made from the core-shell powders are summarized in Table <NUM>. The density and molecular weight of the polymers parts molded at the same conditions as in Table <NUM> are given as comparative reference. No apparent degradation in molecular weight of the polymer was observed. However, there was an increase in molecular weight in compression molded PEI copolymer (CRS5001)-coated Zinc Oxide versus neat PEI copolymer that was compression molded at the same condition.

Relative Density was determined by measuring the density of the molded pellet (Measured Density (ρM)) and comparing that to the Theoretical Density. The Measured Density may be calculated by dividing the volume, determined by measuring the outer dimensions (the volume of other shapes can be determined by any of various known methods, for example by submersion in an incompressible fluid), by the weighing the pellet (determined with a scale or balance). For the present examples, the Measured Density of the samples (e.g., pellets) was determined by the Archimedes method, using a KERN ABS-N/ABJ-NM balance equipped with an ACS-A03 density determination set. In particular, each sample was dried and the dry weight (Wdry) measured. The sample was then subjected to boiling in water for a period of <NUM> to ensure that all voids in the object were filled with the water. The sample when then suspended in the used liquid at a known (non-boiling) temperature to determine the apparent mass in liquid (Wsus). The sample was then removed from the water, and the excess water wiped from the surface of the sample using a tissue moistened with the water. The saturated sample was then immediately weighed in air (Wsat). The density was then determined using Formula (IV): <MAT>.

In the present examples, the quantities of polymer and ceramic in a pellet were known. When the starting proportions are not known, the organic content of the polymer in the compression-molded pellet can be determined by thermogravimetric analysis (TGA) in air, permitting the calculation of the content of ceramic in the compression-molded pellet. The combined density or Theoretical Density (ρT), assuming zero voids/gas content, was then calculated using Formula (IV): <MAT> where mp is the mass of the polymer in the molded pellet, ρp is the density of the polymer, mc is the mass of the ceramic in the molded pellet, and ρc is the density of the ceramic. Relative Density (ρR) is then calculated according to Formula (V): <MAT>.

The molecular weight measurements reported in Table <NUM> and Table <NUM> above, and in Table <NUM> below, were measured via liquid chromatography using an Agilent <NUM> Infinity II HPLC (available from Agilent Technologies, Inc. (Santa Clara, CA, USA)) that comprised an Isocratic Pump, Vialsampler, multi-column thermostat (MCT) to regulate the mobile phase temperature passing through the columns, and a variable wavelength detector (VWD). The system was controlled by Agilent GPC/SEC software, and the measurements performed using known methods.

The measurement of weight changes, programmed as isothermal or linear heating temperature conditions, can be monitored in solid or liquid specimen by the use of a Thermogravimetric Analyzer (TGA). The measurement of weight change, normally weight loss, can result from the degradation (thermal or oxidative) of the specimen, of by the evolution of volatiles below the degradation temperature of the sample. For the TGA measurements discussed herein, less than <NUM> of sample was weighed in a platinum pan, and the TGA test was conducted using a Discovery TGA at hearing rate of <NUM> per minute in air.

Thermal analysis was performed by differential scanning calorimetry (DSC), a method of measuring heat flow as a function of temperature, as well as thermal transitions of samples (e.g., polymers, monomers, and additives) according to a predetermined time and temperature program. These thermal transitions are measured during heating, cooling, or isothermal cycles; and these transitions occur when the material undergoes a physical or chemical change. DSC was carried out on a TA-Q1000 Analyzer at <NUM> C/min.

Rectangular beams were also cut using a CNC mill from the <NUM> pellet produced above for Example <NUM>, and certain mechanical properties determined. In particular, beams were cut to have a rectangular cross section of <NUM> x <NUM>, and were polished using a <NUM> grit sand paper and tested under <NUM>-point bending at a <NUM> per minute (mm/min) displacement rate. Table <NUM> summarizes the measured properties along with reference properties of Al<NUM>O<NUM> alone obtained in literature.

Claim 1:
A method of forming a ceramic-polymer composite powder, the method comprising:
mixing a polymer, solvent, and particles of a ceramic;
where the polymer is selected from the group of polymers consisting of:
polycarbonate (PC) copolymers, polyetherimide (PEI), polyetherimide (PEI) copolymers, polyphenylsulfone (PPSU), polyarylethersulfone (PAES), and polyether sulfones (PES); and
where the ceramic is selected from the group of ceramics consisting of: Al<NUM>O<NUM> , Fe<NUM>O<NUM> , Fe<NUM>O<NUM> , ZnO , ZrO<NUM>, SiO<NUM> , and combinations of any two or more of these ceramics;
dissolving at least partially the polymer in the solvent by superheating the mixture to a first temperature above the normal boiling point of the solvent and while maintaining the mixture at a first pressure at which the solvent remains substantially liquid;
agitating the superheated mixture for a period of minutes while maintaining the mixture at or above the first temperature and at or above the first pressure;
cooling the mixture to or below a second temperature below the normal boiling point of the solvent to cause the polymer to precipitate on the particles of the ceramic and thereby form a plurality of core-shell particles each comprising a core and a shell around the core, where the core comprises a particle of the ceramic and the shell comprises the polymer.