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materials that increase the plasticity and or elasticity of polymers during processing and or use. The use of plasticizers, which are sometimes also called softeners, facilitates the dispersion of fillers and other bulk ingredients in polymers and lowers the temperatures for processing of polymer compositions in industrial equipment. Some plasticizers impart to the polymers nonflammability and resistance to light, heat, and low temperatures, as well as moisture resistance and other desirable special properties.
Substances used as plasticizers are nonvolatile, chemically inert products that are compatible with the polymer, that is, are capable of forming stable compositions with the polymer when introduced in sufficiently large quantities (sometimes up to 100 percent of the weight of the polymer). Common plasticizers include esters of organic and inorganic acids, such as dibutyl phthalate, bis(2-ethylhexyl) phthalate, dibutyl sebacate, and tricresyl and tributyl phosphate; petroleum-refining products, such as petroleum oils; products derived from the processing of coal and wood materials, such as coumarone-indene resins and rosin; and epoxidized vegetable oils.
Various methods are used for the combination of polymers with plasticizers (plasticization), including dispersion of polymers in a solution or emulsion of plasticizers, addition of plasticizers to monomers immediately before polymerization or polycondensation, and introduction of plasticizers into multicomponent polymer compositions. Plasticizers are most widely used in the processing of plastics: about 70 percent of the output of plasticizers is used in the processing of polyvinyl chloride. Plasticizers also play an important role in the production of rubber, paints, and varnishes.