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polyvinylidene chloride[¦päl·i·vī′nil·ə‚dēn ′klȯr‚īd]
(—CH2— CC12—)n, a linear and thermoplastic polymer of vinylidene chloride. Polyvinylidene chloride is a white plastic with a molecular weight of up to 100,000. Its degree of crystallinity is up to 50 percent and its density at 30°C is 1.875 g/cm3.
Physiologically harmless and incombustible, polyvinylidene chloride is rather strong, with a tensile strength of 40 meganew-tons per sq m (MN/m2), or 400 kilograms-force per sq cm (kgf/cm2), and a flexural strength of 100 -110 MN/m2, or 1,000–1,100 kgf/cm2. It is soluble in tri(dimethylamido)phos-phate and some alkyl sulfones and is resistant to the action of acids, alkalies, hydrocarbons, alcohols, esters, and ethers. It is somewhat sensitive to a 95 percent solution of H2SO4, to concentrated solutions NaOH and NH3, and to electron irradiation, light, and heat. Its thermal properties are similar to those of polyvinyl chloride.
In industry, polyvinylidene chloride is produced by free-radical polymerization of a monomer in an emulsion. A variety of tubes are produced from polyvinylidene chloride by extrusion, and fibers and films are formed from its solutions. In the USA, fibers are produced that are known by the trade name Rovana. Solutions of polyvinylidene chloride are also used in the paint and varnish industry. Its emulsions are used to impregnate fabrics, leathers, and paper.
Because of the difficulties involved in the processing and stabilization of polyvinylidene chloride, copolymers of vinylidene chloride have acquired greater practical importance, especially the copolymers with vinyl chloride, acrylonitrile, and several dienes. The monofilament made from the vinylidene chloride copolymer with vinyl chloride is produced under various trade names: Soviden (USSR), Saran (USA, Great Britain), Vestan (Federal Republic of Germany), and Kurehalon (Japan). Copolymers with acrylonitrile are produced as latexes and solid products, such as Saran in the USA. In the USSR, a fiber from such a copolymer—Saniv—is characterized by increased resistance to light.
The world production of polyvinylidene chloride and its copolymers in 1973 was 80,000 tons.
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K. S. MINSKER