Abstract: Disclosed is a polylactic acid/polycarbonate resin composition including (A) about 100 parts by weight of a mixed resin including: (a1)) about 10 to about 90 wt % of a polycarbonate resin and (a2) about 10 to about 90 wt % of a polylactic acid resin; (B) about 1 to about 50 parts by weight of a flame retardant based on about 100 parts by weight of the mixed resin; (C) about 1 to about 30 parts by weight of an acryl-based copolymer based on about 100 parts by weight of the mixed resin; and (D) about 1 to about 20 parts by weight of an impact-reinforcing agent based on about 100 parts by weight of the mixed resin.

Abstract: A process for the preparation of plastic molded articles which can be used in the dental field, the process including the steps of: mixing A) at least one polymerizable component and B) at least one initiator in desensitized form to form a paste having a consistency does not demix during injection; injecting the paste into a cuvette; and polymerizing the mixture by applying heat.

Abstract: A process for the preparation of vinylaromatic (co)polymers grafted on an elastomer in a controlled way, comprising the dissolving of an elastomer, such as polibutadiene, in a mixture consisting of a monomer and of a solvent in the presence of a polymerization catalytic system, which comprises an initiator of free radicals and a stable initiator of free radicals. The mixture obtained in this way is heated to a temperature of about 100° C. to functionalize the rubber, then more monomer is added and the temperature is raised to start the polymerization reaction.

Abstract: This invention relates to a method for producing functionalized cis-1,4-polydienes having a combination of a high cis-1,4-linkage content and a high functionality, the resulting polymers and the vulcanized products containing the polymers. The functionalized cis-1,4-polydienes of the present invention are produced by a method comprising the steps of: (1) preparing a reactive polymer by polymerizing conjugated diene monomer with a lanthanide-based catalyst in the presence of less than 20% by weight of organic solvent based on the total weight of monomer, organic solvent, and resulting polymer, where the lanthanide-based catalyst is the combination of or reaction product of (a) a lanthanide compound, (b) an aluminoxane, (c) an organoaluminum compound other than an aluminoxane, and (d) a halogen-containing compound; and (2) contacting the reactive polymer with a functionalizing agent.

Abstract: The present invention relates to acryl-silicone hybrid impact modifiers, the method of their manufacture, and vinyl chloride resin compositions containing the above. The acryl-silicone hybrid impact modifier of the present invention contains a seed obtained through emulsion copolymerization of vinyl monomers and hydrophilic monomers; an acryl-silicone hybrid rubber core covering the seed in which a polyorganosiloxane rubber phase is dispersed locally onto the inner part and surface of the acrylic rubber core containing alkyl acrylate polymers and a shell covering the above rubber core and containing alkyl methacrylate polymers. Thermoplastic resins containing the above, particularly by being added to vinyl chloride resins, they have effects of granting superior impact resistance, weatherability, and high gloss.

Abstract: Provided are a rubber latex having a multi-layer structure, wherein an inner-layer rubber latex has a refractive index greater than that of an outer-layer rubber latex, a graft copolymer prepared from the rubber latex, a polyvinyl chloride (PVC) resin blend containing the graft copolymer, and a method of preparing the rubber latex. The PVC resin blend containing the graft copolymer including the rubber latex according to the present invention has improved color property and low-temperature impact strength than conventional PVC resins.

Abstract: A copolymer of formula 1 in which M1 is a unit obtainable from ring opening metathesis polymerization (ROMP); R is an alkyl, ether, ester or aryl unit; M2 and M3 are independently selected from units obtainable by reversible addition fragmentation chain transfer polymerization (RAFT); X is a terminal unit selected from the group consisting of dithioester, trithiocarbonate, xanthate; and m is an integer from 2 to 1 million, n is an integer from 2 to 500,000 and k is an integer from 2 to 500,000.

Abstract: Disclosed is a silicone impact modifier with a high refractive index. The silicone impact modifier can include (A) a rubber core including (a1) an organosiloxane cross-linked (co)polymer with a particle size of about 50 to about 400 nm and (a2) an alkylacrylate-styrenic aromatic compound cross-linked copolymer; and (B) a plastic shell including a vinyl (co)polymer. The refractive index of the silicone impact modifier of the present invention can be about 1.49 to about 1.59.

Abstract: Disclosed herein are a polycarbonate resin composition and a plastic article produced from the resin composition. The polycarbonate resin composition includes about 85 to about 99 parts by weight of a polycarbonate resin and about 1 to about 15 parts by weight of a core-shell graft copolymer, wherein the core-shell graft copolymer has a core-shell structure in which a vinyl monomer including methyl methacrylate and phenyl methacrylate is grafted onto a rubber.

Abstract: The present invention provides a process for preparing emulsion polymer particles of a hollow core/shell structure in the presence of a monomer plasticizer having a ceiling temperature less than 181° C. wherein a polymerization inhibitor or reducing agent is not added to the aqueous emulsion of the core shell particles during the neutralization and swelling stage. The obtained core shell particles are useful in paints, paper coatings, foams, and cosmetics.

Abstract: The invention discloses thermosetting water-based paint comprising water-dispersible acrylic polymer particles which are obtained through multi-stage emulsion polymerization of radical polymerizable unsaturated monomers using a specific reactive emulsifying agent, said monomers comprising amido-containing radical polymerizable unsaturated monomer having at least 2 radical polymerizable unsaturated groups per molecule, methacrylic acid and hydroxyl-containing radical polymerizable unsaturated monomer; and coating film-forming methods which use the thermosetting water-based paint.

Abstract: Disclosed is a powdered polymeric lubricant having a multi-layer structure as a processing aid capable of being used to improve processability of a vinyl chloride resin, and a manufacturing method thereof. The powdered polymeric lubricant having multi-layer structure according to the present invention has an excellent ability to prevent its adhesion to a metal surface upon its processing so as to give a long-term workability to extrusion, calendaring, blow molding, injection molding, etc., when a small amount of the powder of the present invention is mixed with a vinyl chloride resin. Accordingly, the present invention provides a powdered polymeric lubricant capable of controlling compatibility with the vinyl chloride resin and minimizing the adhesive property to a metal surface of a processing machine when a vinyl chloride resin is processed with a polymer including a silicone-based polymer.

Abstract: The invention relates to a process for preparing (meth)acrylate-based ABA triblock copolymers with an olefinic functionalization of the A blocks.

Abstract: A novel copolymer, graft copolymer, copolymer particles, flame retardant, and resin composition are provided. A copolymer including a polymer (A) segment having a glass transition temperature not more than ?10° C., and a polymer (C) segment having at least a unit derived from a monomer (B) which has two or more of aromatic rings and one or more radical reactive groups in one molecule; a graft copolymer having the component (B) grafted onto the component (A); and copolymer particles thereof are obtained. A flame retardant resin composition is obtained by using the copolymer as a flame retardant and blending the flame retardant with the resin.

Abstract: The present invention discloses a method of making core-shell polymer particles, comprising forming a linking-group-containing polymer by derivatizing a hydroxy-group-containing polymer, comprising hydroxy groups on adjacent carbon atoms with a linking agent, that is a compound comprising both an aldehyde moiety and an amine moiety, wherein one or more acetal moieties are formed in the linking-group-containing polymer, each acetal formed by the reaction of the aldehyde moiety in the linking agent with two hydroxy groups in the linking-group-containing polymer, wherein the amine moiety then becomes a linking group pendent from the linking-group-containing polymer, wherein the linking group is capable of reacting with a precursor group in the precursor polymer. Also disclosed are compositions comprising insoluble core-shell particles made by the method.

Abstract: This invention discloses a process for synthesizing a modified crosslinked elastomeric particle which comprises a two-step polymerization of a conjugated diolefin monomer and a vinyl aromatic monomer by emulsion polymerization, wherein the particle is synthesized by the steps of (1) polymerizing a conjugated diolefin monomer, alone or in combination with a vinyl aromatic monomer, and optionally a crosslinking monomer, to create a crosslinked elastomeric core having residual double bonds and an outer surface; (2) polymerizing a monomer of a vinyl aromatic monomer, alone or in combination with a diolefin monomer, to create a polymeric shell, wherein the polymeric shell is grafted to the outer surface of the polymeric core by reacting with the residual double bonds of the polymeric core; and (3) coagulating the core-shell emulsion latex solution to recover the particles.

Abstract: This invention relates to coating compositions that include water; a latex polymer and a silane coupling agent. The latex polymer preferably comprises acetoacetoxy functionality, or is a multistage latex, or is an acetoacetoxy functional multistage latex. The silane coupling agent is preferably a functionalized silane coupling agent (more preferably an epoxy-functional silane coupling agent). The compositions may be used to coat a variety of substrates, including wood, cement and fiber cement. Articles having the coating applied thereto are also provided.

Abstract: Coating compositions for cementitious substrates may be made from a silane-functional multistage latex polymer. The compositions adhere well to cementitious substrates and resist crush damage such as may be caused by stacking coated substrate boards.

Abstract: A core-shell particle is formed by a method that includes forming a crosslinked polyorganosiloxane core, reacting a graftlinking agent with the crosslinked polyorganosiloxane core, and polymerizing a poly(alkenyl aromatic) shell around the graftlinking agent-functionalized polyorganosiloxane core. The method produces a core-shell particle with improved adhesion between shell and core. The core-shell particle is useful as an impact modifier in thermoplastic compositions.

Abstract: Process for improving the brilliance of color and the stability of a colored polymer system, which is composed of a matrix and of discrete polymer particles distributed in accordance with a defined spatial lattice structure in the matrix, and which is obtained by filming of an emulsion polymer with core/shell structure, which comprises using an emulsion polymer obtainable by polymerizing monomers in at least one first stage (core monomers), then polymerizing monomers in at least one further, second stage (transition stage), and finally polymerizing monomers in a third stage (shell monomers), where, based on the percentage constitution of the monomer mixtures of the three stages, at most 30% by weight of the monomers of the first stage are identical with those of the third stage, and 5% of the monomers of the second stage are identical with, respectively, those of the first and those of the third stage, and not more than 60% by weight of the monomers of the 2nd stage here are monomers absent in the 1st sta

Abstract: The present invention relates to an acryl-silicon rubber complex polymer which has a seed-core-shell structure wherein vinyl monomer and hydrophilic monomer are cross-linked on the seed; the acryl-silicon complex IPN core having an IPN (interpenetrating network) structure formed by radical polymerization of acryl monomer and hydrosilyation of silicon rubber in which silicon rubber particles are dispersed by being cross-linked to acryl rubber, in a continuous phase, is formed on the seed; and a shell prepared by graft-polymerization of C1-C4 alkyl methacrylate to the acryl-silicon complex IPN core is formed on the core, and a method of preparation and use of the same, thereby having excellent impact resistance, weatherability and gloss, so that it can be effectively used as an impact modifier for vinyl chloride resin.

Abstract: A method for producing magnetic particles includes forming a hydrophobic first polymer layer on the surface of a mother particle containing superparamagnetic particles, forming a second polymer layer having glycidyl groups at least on its surface on the first polymer layer, and introducing a polar group containing one or more of at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, and a sulfur atom by chemically modifying the glycidyl groups.

Abstract: This invention discloses a process for synthesizing a modified crosslinked elastomeric particle which comprises a two-step polymerization of a conjugated diolefin monomer and a vinyl aromatic monomer by emulsion polymerization, wherein the particle is synthesized by the steps of (1) polymerizing a conjugated diolefin monomer, alone or in combination with a vinyl aromatic monomer, and optionally a crosslinking monomer, to create a crosslinked elastomeric core having residual double bonds and an outer surface; (2) polymerizing a monomer of a vinyl aromatic monomer, alone or in combination with a diolefin monomer, to create a polymeric shell, wherein the polymeric shell is grafted to the outer surface of the polymeric core by reacting with the residual double bonds of the polymeric core; and (3) coagulating the core-shell emulsion latex solution to recover the particles.

Abstract: An aqueous inkjet ink composition suitable for printing on a hydrophobic surface such as a vinyl surface including an aqueous vehicle, a self-dispersed pigment, a silicone-containing surfactant and an aqueous emulsion polymer having a glass transition temperature (Tg) of from ?40° C. to 150° C. Also provided is a method for printing an image on a hydrophobic substrate.

Abstract: The invention describes a novel impact modifier, built up from core-shell1- and shell 2, the core being capable of plastic deformation. Good mechanical properties were achieved using a small amount of impact modifier.

Abstract: A novel method of preparing an aqueous dispersion of non-uniform polyurethane particles which comprises (a) preparing at least two isocyanate-terminated polyurethane prepolymers having different hydrophilicities; (b) preparing a uniform mixture of said prepolymers; and (c) dispersing the mixed prepolymers in an aqueous medium. The resulting dispersion of the prepolymers may optionally be chain extended. This method enables the preparation of core-shell particles as well as particles of other morphologies, including “raspberry”, interpenetrating network, “salt-and-pepper”, “ice-cream cone” and particles of gradient composition. Similarly, an aqueous dispersion of two different polyurethane polymers may be obtained by first preparing at least two different isocyanate-terminated polyurethane prepolymers, preparing a uniform mixture of such prepolymers and thereafter dispersing the mixture in an aqueous medium.

Abstract: The present invention relates to a transparent thermoplastic resin composition which characteristically contains A) 20-80 weight % of graft copolymer composed of a) conjugated diene rubber latex; b) intermediate layer prepared by copolymerization of acrylic acid alkylester derivative and aromatic vinyl derivative with the above a); and c) graft layer prepared by copolymerization of methacrylic acid alkylester derivative or acrylic acid alkylester derivative, a romatic vinyl derivative and vinyl cyan derivative with the above b) and B) 20-80 weight % of MSAN copolymer prepared by copolymerization of methacrylic acid alkylester derivative or acrylic acid alkylester derivative, aromatic vinyl derivative and vinyl cyan derivative.

Abstract: Methods and systems for modifying a polymer are disclosed herein. A matrix is generally provided having a surface thereof, wherein the matrix comprises a plurality of hyperbranched polymers. The plurality of hyperbranched polymers can be chemically bound to a plurality of surfactants or order to modify the surface and produce a polymeric material thereof. The surface is tailored with a plurality of functional groups that self-assemble and are deliverable to the surface of the solution, including interfaces thereof, thereby permitting a high-density assembly of functional groups to operate in concert with one another in order to generate a modified surface thereof. The polymeric material produced thereof can be reversibly adaptable to environmental conditions through a blooming of varying surface functional group to the surface of the solution.

Abstract: An aqueous polymer emulsion comprising water and swollen multi-stage polymer is provided. The swollen multi-stage polymer has low dry bulk density, as measured by centrifugation. To achieve the low dry bulk density, the polymer is highly swollen in such a way that it does not subsequently collapse. The polymer is useful in paint and paper coatings.

Abstract: Porous films are provided which include a blend of a film forming polymer and a non-film forming material, the film having a network of pores or channels throughout the film. The porous polymer films are formed between 0° and 80° C., retain porosity at elevated temperatures and are non-friable. A process for preparing porous polymer films and their applications are disclosed.

Abstract: In order, in the case of a moulding composition for the production of sanitary-ware components, comprising a methyl-methacrylate-based syrup and from 50 to 85%, expressed in terms of the moulding composition, of an inorganic filler, to obtain an improvement in the scratch-proofness and the abrasion resistance of the shaped components which are obtained therefrom, it is proposed that the composition furthermore comprise elastomer particles or elastomer particle aggregates having a particle size <100 ?m in an amount in the range of 5% by weight to <20% by weight, expressed in terms of the mass of the syrup.

Abstract: In one aspect, the invention provides a water-based release coating composition comprising a mixture of: A. from 0.1 to about 5 wt % of a fluoro(meth)acrylate (co)polymer or a fluorochemical urethane compound containing at least one fluorinated group having the formula —CF2)nCF3, wherein n is an integer from 1 to 3; B. from about 5 to about 99.9 wt % of a copolymer comprising the reaction product of a. from about 40 to about 70 wt % of an alkyl (meth)acrylate, wherein the alkyl group contains from 16 to 22 carbon atoms, b. from about 3 to about 20 wt % of (meth)acrylic acid, c. from about 20 to about 40 wt % acrylonitrile, and d. from 0 to about 15 wt % of vinyl monomer, other than acrylonitrile, wherein the sum of a. through d. equals 100%; and C. from 0 to about 94.9 wt % of an extender polymer, wherein the sum of A., B., and C. is 100% and wt % is based on the total amount of solids in the composition.

Abstract: A water-based ink for ink-jet printing, comprising colored particles containing: (a) a core particle having a colorant; and (b) a shell having a resin and encapsulating the core particle, wherein the resin comprises a monomer unit having a hydroxyl group in an amount of 0.1 to 50 weight % based on the total weight of the shell.

Abstract: A core-shell particle including a core with poly(arylene ether) and a shell with an ethylenically unsaturated copolymer is described. Also described are a method of forming the particle, a composition including the particle, and an article including such a composition.

Abstract: The present invention concerns a waterborne copolymer dispersion comprising at least one alkenyl functional dendritic polymer being copolymerized to the polymer backbone of at least one homo or copolymer obtainable by polymerization, such as emulsion polymerization, in an aqueous medium of at least one at least one polymerizable allyl, vinyl, maleic or diene monomer. The dendritic polymer is built up from a dendritic core polymer and at least one alkenyl functional compound bonded to the core polymer. In a further aspect the present invention concerns the use of said copolymer dispersion.

Abstract: The plastics additives powder compositions of the present invention are provided as powder particles having impact modifier particles and processing aid particles which are coagulated and dried. When blended in thermoplastic resins, such as PVC, the subject plastics additives powders both increase the impact strength and improve process efficiency and melt strength. The impact and processing properties achieved by the present invention are more efficient than using separate impact modifier and processing aid powders. The method of preparing the powder compositions of the present invention also enable impact modifier particles having rubber weight fractions greater than 88% to be isolated as free-flowing powders.

Abstract: The invention relates to a novel impact-resistance modifier, constructed from a core-shell 1 and a shell 2, whereby the core is plastically deformable. The invention is characterised by excellent mechanical properties obtained by a low content of impact-resistance modifier.

Abstract: The invention relates to an acrylic impact modifier having a core-shell structure that provides an acrylic impact modifier composition comprising (a) a rubber core containing an alkyl acrylate polymer comprising at least two layers having different cross-linking densities, and (b) a shell containing an alkyl methacrylate polymer; to a process for the preparation of the acrylic impact modifier; and to a poly(vinyl chloride) composition comprising it. The acrylic impact modifier imparting excellent impact resistance was invented by employing multi-stage polymerization and at the same time by controlling the swelling index of rubber particles by changing the degree of cross-linking from stage to stage. And the poly(vinyl chloride) comprising the impact modifier of the present invention has good weatherability as well as excellent impact strength.

Abstract: A powdery linear polymer having a narrow particle size distribution with little dusting and excellent in anti-blocking property is recovered from a latex of a linear polymer containing a large proportion (35–75 wt. %) of soft polymer (S) component through a two-step coagulation process including a first (moderate coagulation) step causing 70–98 wt. % of the coagulation. The linear polymer in the latex has a multilayer structure comprising a linear polymer (S) having a glass transition temperature below 40° C. and a linear polymer (H) having a higher glass transition temperature disposed in totally at least two layers and containing 35–75 wt. %, as a whole, of the linear polymer (S) with the proviso that the linear polymer (S) cannot be contained in excess of 30 wt. % in an outermost layer of the multilayer structure.

Abstract: Disclosed herein is a silicone-acrylate impact modifier composition, where the impact modifier composition comprises structural units derived from: at least one silicone rubber monomer, a branched acrylate rubber monomer having the formula: wherein R1 is selected from hydrogen and C1-C8 linear and branched hydrocarbyl groups, R2 comprises a branched C3-C16 hydrocarbyl group; and “z” is greater than or equal to 3; a first graft link monomer; a polymerizable alkenyl-comprising organic material; and a second graft link monomer The silicone-acrylate impact modifier compositions disclosed herein are useful for making molding compositions, which are useful for producing various articles, especially for outdoor applications.

Abstract: An acrylic polymer powder obtained by coagulating and drying a latex containing acrylic polymer particles, in which acrylic polymer powder, the average particle size of the powder is 5 to 10 ?m, the percentage of void is 70% or less, and the integral void volume on voids having a pore diameter of 1 ?m or more is 0.9 mL/g or less. Acrylic sol obtained using the powder is excellent in storage stability and fluidity. The storage stability and fluidity of the acrylic sol can further be heightened, or it is possible to give different effects (enhancement of mixing properties of the powder with a plasticizer; lowering of the viscosity of the acrylic sol, enhancement of particle destruction resistance; enhancement of the bleed-out resistance, film uniformity and flexibility of moldings obtained from the acrylic sol, formation of smooth film; etc.

Abstract: At least one of a hollow particle 14, a porous particle 24, and a solid particle 34 having the pores 18, 28, 38 on the surface thereof is subjected to plasma irradiation under a reduced pressure while changing plasma irradiation intensity and/or the degree of vacuum. After the plasma irradiation, at least one type of monomer is graft polymerized onto the surface of the plasma irradiated particle by contact between the at least one type of monomer and the particle so as to substantially fill the pores 18, 28, and 38 of the particle with grafted polymers 12 of the monomers.

Abstract: The present invention relates to thermoplastic polyesters, which comprise, by weight: (i) a thermoplastic polyester; (ii) an impact modifier comprising: (a) a core-shell copolymer (A); (b) an ethylene copolymer (B) chosen from ethylene-unsaturated carboxylic acid anhydride copolymers (B1), ethylene-unsaturated epoxide copolymers (B2) and blends thereof; (iii) the (B)/(A) ratio being between 40/60 and 10/90 for proportions of impact modifier between 18 and 40% in 82 to 60% of polyester, respectively; (iv) the (B)/(A) ratio being between 40/60 and 25/75 for proportions of impact modifier between 2 and 18% in 98 to 82% of polyester, respectively. It is particularly useful for PET and PBT.

Abstract: The present invention relates to aqueous plastic material dispersions based on vinyl ester copolymers, having a solids content of up to 80% by weight and a minimum film formation temperature below 20° C., which is substantially stabilized by ionic components, the vinyl ester copolymers containing at least one homo- or copolymer A and at least one homo- or copolymer B, methods for producing the same and the use thereof.

Abstract: Pigmented aqueous coating composition providing good blocking and elasticity properties comprises a blend of a seeded multistage polymer latex(es) having at least one soft and at least one hard polymer phases and a non-film-forming polymer latex(es), the seed polymer(s) having a Tg?10° C. lower than that of the hard polymer phase(s) and preferably having a Tg?10° C. higher than that of the soft polymer phase(s), and the multistage polymer(s) preferably having amino functionality incorporated by an imination reaction.

Abstract: The present invention is directed to a process for the preparation of polysaccharide grafted latex particles wherein the polysaccharide has ?-1,4 linkages, wherein the process comprises core/shell emulsion polymerisation. Preferably, the process comprises a single step of preparing the latex particles by emulsion polymerisation of latex monomers with the simultaneous grafting of the polysaccharide.

Abstract: Combustible core-shell particles have a nitro-resin core that is covered by an addition polymer shell in a weight ratio of from 20:1 to 0.2:1 (core:shell). The shell polymer is derived from one or more ethylenically unsaturated polymerizable monomers that are represented by the following Structure I: CH2?C(R)-X??(I) wherein R is hydrogen or methyl, and X is any monovalent moiety except a phenyl group. These combustible core-shell particles are particularly useful in thermal imaging materials such as “direct-write” printing plate precursors.

Abstract: A film receptive to a variety of different classes or kinds of inks, such as water based inks, solvent based inks and UV cured inks. The film includes a water based latex polymer, such as transparent film-forming core/shell latex polymers, a polar polymer, such as polymers having an ionic component to increase the receptivity of the coating to water-based inks, and a surfactant, such as an alkyaryl sulfonate, to prevent agglomeration of the latex polymer before it is formed into film. The preferred latex polymer is a core/shell latex polymer. The preferred polar polymer is chemically compatible with latex polymers and is sufficiently ionic or polar to improve the printability onto the film of water-based inks. The surfactant, which may be in the latex as manufactured or may be added separately, has a molecular structure that includes at least one hydrophobic moiety and at least one anionic group such as sulfates, sulfonates and the like.

Abstract: Dispersions of hybrid polyurethane particles are made using miniemulsion techniques. An isocyanate-terminated prepolymer and a monomer are mixed and dispersed in an aqueous phase to form a dispersion of droplets. All droplets are polymerized and chain-extended in one step to form hybrid particles containing a polyurethane and a polymer of the monomer. This process provides a simple method of making hybrid particles, in which particle size and the number of particles is controlled in the mixing step. The hybrid particles often have a core-shell morphology, with the polyurethane being concentrated in the shell and the polymer being concentrated in the center of the particle.

Abstract: An epoxidized granular thermoplastic polymer which comprises a shell-like surface layer insoluble in toluene at 25° C.