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polystyrene(pŏl'ēstī`rēn), widely used plasticplastic,
any organic material with the ability to flow into a desired shape when heat and pressure are applied to it and to retain the shape when they are withdrawn. Composition and Types of Plastic
..... Click the link for more information. ; it is a polymerpolymer
, chemical compound with high molecular weight consisting of a number of structural units linked together by covalent bonds (see chemical bond). The simple molecules that may become structural units are themselves called monomers; two monomers combine to form a dimer,
..... Click the link for more information. of styrene. Polystyrene is a colorless, transparent thermoplastic that softens slightly above 100°C; (212°F;) and becomes a viscous liquid at around 185°C; (365°F;). It is resistant to acids, alkalies, oils, and alcohols. It is produced either as a solid or as a foamed plastic marketed under the trade name Styrofoam. Its many uses include electrical and thermal insulation, translucent window panels, storage-battery cases, and toilet articles.
a linear polymer of styrene, [—CH2— CH(C6H5) —]n; a clear vitreous substance. Moleculer weight, 30,000–500,000; density, 1.06 g/cm3 (20°C); glass transition point, 93°C.
Polystyrene is an inexpensive, large-tonnage thermoplastic resin. It has high hardness and good dielectric properties; it is weatherproof and readily dyeable and moldable. It is chemically stable and soluble in aromatic and chlorinated aliphatic hydrocarbons, and it is physiologically harmless. However, it has relatively low heat resistance (Vicat softening point, about 100°C) and high brittleness; various styrene copolymers have better use properties. For example, copolymerization of styrene with acrylonitrile or α-methylstyrene increases heat resistance and tensile strength by about 60 percent; an increase in strength and impact strength from 5–10 to 50–100 kilojoules per sq m, or kilograms = force · cm per sq cm, is achieved by production of graft styrene copolymers with 5–10 percent rubber—for example, butadiene (impact-resistant polystyrene)—or triple copolymers of acrylonitrile, butadiene, and styrene (ABS polymers). Transparent triple copolymers are synthesized upon substitution of methyl methacrylate for acrylonitrile.
Polystyrene and styrene copolymers are produced in industry by radical polymerization in bulk or in aqueous emulsions; they are processed by injection molding, extrusion, compression molding, and vacuum forming.
Polystyrene is used in the manufacture of household appliances and domestic items, packing material, toys, accessories, and films, as well as in the preparation of polystyrene foam. In addition, impact-resistant polystyrene and ABS polymers are used in the manufacture of radio and television housings, motor vehicle and refrigerator parts, furniture, and pipes. Polystyrene is also mixed with rubber and with other plastics.
World production of polystyrene and styrene copolymers in 1973 was about 5 million tons.
REFERENCESHouwink, R., and A. Staverman [compilers]. Khimiia i tekhnologiia polimerov, vols. 1–2 (parts 1–2). Moscow-Leningrad, 1965–66. (Translated from German.)
See also references under .
S. A. VOL’FSON