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polyvinyl chloride(PVC), thermoplastic that 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 vinyl chloride. Resins of polyvinyl chloride are hard, but with the addition of plasticizers a flexible, elastic 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the ability to flow into a desired shape when heat and pressure are applied to it and to retain the shape when they are withdrawn.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. can be made. This plastic has found extensive use as an electrical insulator for wires and cables. Cloth and paper can be coated with it to produce fabrics that may be used for upholstery materials and raincoats.
(—CH2—CHCl—)n, a predominantly linear and thermoplastic polymer of vinyl chloride. It is a white plastic with a molecular weight of 6,000–160,000. Its degree of crystallinity is 10–35 percent, and its density at 20’C is 1.35–1.43 g/cm3. Polyvinyl chloride is physiologically harmless.
Polyvinyl chloride is rather strong, with a tensile strength of 40–60 meganewtons per sq m (MN/m2), or 400–600 kilograms-force per sq cm (kgf/cm2), and a flexural strength of 80–120 MN/m2, or 800–1,200 kgf/cm2. It is a good dielectric. It is limitedly soluble in ketones, esters, and chlorinated hydrocarbons and is resistant to the action of moisture, acids, alkalies, salt solutions, gasoline, kerosene, fats, alcohols, and industrial gases, such as NO2, Cl2, SO3, and HF. Effective plasticizers for polyvinyl chloride include phthalates, phosphates, and sebacates. Polyvinyl chloride is resistant to oxidation and virtually incombustible. It has low heat resistance, with a Martens yield temperature of 50°-80°C. At temperatures above 100°C, it decomposes markedly and loses HC1, which may result in the polymer acquiring a color ranging from yellowish to black. Decomposition is accelerated in the presence of O2, HCl, and some salts; it is also accelerated by strong mechanical action and by the action of ultraviolet, beta, and gamma radiation. Polyvinyl chloride is chlorinated to raise its heat resistance and improve its solubility.
In industry, polyvinyl chloride is obtained by the free-radical polymerization of a monomer in a bulk, emulsion, or suspension. Its major properties and uses are determined by the method of polymerization. Polyvinyl chloride produced by bulk or suspension polymerization is used in the production of rigid, semisoft, and soft (or plasticized) plastics, which are processed by pressing, injection molding, extrusion, or calendering. The pasty variety of emulsion polyvinyl chloride is used mainly in the production of such items as synthetic leathers and expanded plastics, which are made of plastisols and organosols.
Polyvinyl chloride is one of the most commonly used plastics. It is utilized in the production of more than 3,000 types of materials and items. It is used for various purposes in the elec-trotechnical, light, and food industries, in ship and heavy machine building, in agriculture and medicine, and in the production of construction materials.
World production of polyvinyl chloride in 1973 was about 8 million tons.
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K. S. MINSKER