Poly styrene Elastomers

Elastomeric styrene containing compounds, such as styrene-buta-diene-styrene block copol mriers, or styrene-isoprene-styrene block copolymers, including its hydrogenated homologues, all of them containing vegetal or even mineral oils in their formulations, can be made biodegradable (13). This is achieved by the admixture of brewer s yeast or yeast mother in amounts of 1-4%. 

Advantageously, modified yeasts can be used to reduce the t) i-cal odor of yeast, such as partially hydrolyzed yeasts (14). 

The yeast can be added to the raw materials before mixing and melting to obtain the composition. Alternatively, the yeast can be added before compounding process. 

For example, the styrenic block copolymer, natural oil and brewer s yeast are mixed to obtain a semifluid product that is extruded at a temperature of about 120-180°C in such a way to obtain granules or pellets. The biodegradable compound can be used in an additional extrusion or molding process to get the final biodegradable product. Thus, a final pol)mieric material-based product is formed, that is biodegrading in a reasonable period of time in suitable composting sites (13). 

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Thermoplastic elastomers are often multiphase compositions in which the phases are intimately dispersed. In many cases, the phases are chemically bonded by block or graft copolymerization. In others, a fine dispersion is apparentiy sufficient. In these multiphase systems, at least one phase consists of a material that is hard at room temperature but becomes fluid upon heating. Another phase consists of a softer material that is mbberlike at RT. A simple stmcture is an A—B—A block copolymer, where A is a hard phase and B an elastomer, eg, poly(styrene- -elastomer- -styrene). 

Commercially, the poly(styrene- -elastomer- -styrene) materials are made by anionic polymerization (7,45—47). An alkj thium initiator (RLi) first reacts with styrene [100-42-5] monomer ... 

Thermoplastic polymers, such as poly(styrene) may be filled with soft elastomeric particles in order to improve their impact resistance. The elastomer of choice is usually butadiene-styrene, and the presence of common chemical groups in the matrix and the filler leads to improved adhesion between them. In a typical filled system, the presence of elastomeric particles at a level of 50% by volume improves the impact strength of a brittle glassy polymer by a factor of between 5 and 10. 

Cao X. and Faust R., Polyisobutylene based thermoplastic elastomer 5. Poly(styrene-b-isobutylene-b-styrene) tri-block copolymers by coupling of living poly(styrene-b-isobutylene) di-block copolymers. Macromolecules, 32, 5487, 1999. 

Jacob S., Majoros I., and Kennedy J.P., Novel thermoplastic elastomers Star-blocks consisting of eight poly(styrene-b-isobutylene) arms radiating from a calex[8]arenecore. Rubber Chem. TechnoL, 71, 708, 1998. 

Maleimides Alkyl and aryl maleimides in small concentrations, e.g., 5-10 wt% significantly enhance yield of cross-link for y-irradiated (in vacuo) NR, cw-l,4-polyisoprene, poly(styrene-co-butadiene) rubber, and polychloroprene rubber. A-phenyhnaleimide and m-phenylene dimaleimide have been found to be most effective. The solubihty of the maleimides in the polymer matrix, reactivity of the double bond and the influence of substituent groups also affect the cross-fink promoting ability of these promoters [82]. The mechanism for the cross-link promotion of maleimides is considered to be the copolymerization of the rubber via its unsaturations with the maleimide molecules initiated by radicals and, in particular, by allyfic radicals produced during the radiolysis of the elastomer. Maleimides have also been found to increase the rate of cross-linking in saturated polymers like PE and poly vinylacetate [33]. 

Poly(styrene) 1839 1930 Thermoplastics, foams Methyl rubbers 1912 1915 Elastomers... 

Plastomers. The production of resins (polyfvinyl chloride], polystyrene, and poly [styrene-co-acrylonitrile]) with relatively high toughness has been one of the most important aims of industry. This can be achieved by modifying a rigid chain with small amounts of elastomers. The best results have been obtained by the use of block and graft copolymers. 

Z. Fodor and R. Faust, Polyisobutylene-based thermoplastic elastomers. IV. Synthesis of poly (styrene-block-isobutylene-block-styr-ene) triblock copolymers using n-butyl chloride as solvent, J. Macromol. Sci.-Chem., 33(3) 305-324, March 1996. 

Sulfur-vulcanizable elastomers have been prepared that are designed to reduce hysteresis in tires by reducing the number of polymer free ends. The method for this preparation entails anionically preparing poly(styrene-co-butadiene) using a lithium thioacetal initiator followed by incorporation of a vulcanization agent into the elastomer terminus. 

The first commercial thermoplastic elastomers deriving their properties from an ABA block copolymer structure were poly(styrene-isoprene-styrene) and poly (styrene-butadiene-styrene) triblocks introduced in 1965 at an ACS Rubber... 

Vulcanization is an industrial process applied to various polymers from the class of unsaturated polyhydrocarbons. The major practical use of vulcanized elastomers is the tire industry. Tires are made from various polymer blends, including natural rubber, typically between 20 and 50%. The other polymers used in various blends that can be vulcanized include copolymers such as poly(styrene-co-1,3-butadiene) or SBR, poly(acrylonitrile-co-1,3-butadiene-co-styrene) or ABS, poly(isobutylene-co-isoprene), poly(ethylene-co-propylene-co-1,4-hexadiene, etc. 

Arguably the most important amorphous ionomer is sulfonated polystyrene (SPS). Other ionomers include poly(styrene-rfln-methacrylic acid) (SMAA), polyurethanes, siloxanes, butadiene-based elastomers, ethylene-propylene-diene terpolymers, acrylates and methacrylates, polyphosphoesters, polyimides, and many others. ... 

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