POLYTETRAFLUOROETHYLENE

(PTFE) a strong, tough, waxy, nonflammable resin belonging to the family of organic polymers, substances composed of large molecules formed by chemical combination of many small ones (monomers) into chains or networks. Known by the abbreviation PTFE or the trade name Teflon, it is distinguished by its complete indifference to attack by almost all chemicals and by its slippery surface; it retains its physical properties over a wide temperature range (-270 to 250 C, or -450 to 480 F). These qualities suit polytetrafluoroethylene to uses in gaskets, bearings, linings for containers and pipes, and parts for valves and pumps that must operate in corrosive environments and for protective coatings on cooking utensils, saw blades, and other articles. Polytetrafluoroethylene forms upon treating tetrafluoroethylene with oxygen; the monomer is made by heating chlorodifluoromethane at about 600-750 C (about 1,100-1,400 F). The chemical and physical properties of PTFE necessitate a special technique for fabricating it into solid articles: a suspension of the powder in a diluent is molded into the desired shape, the diluent is removed by evaporation, and the object is consolidated by sintering (heating to a temperature sufficient to cause the particles to adhere to each other without actually melting). Polymerization of mixtures of tetrafluoroethylene and hexafluoropropylene yields rubbery products that have high resistance to heat and chemical attack; these substances, called Viton, are used in gaskets and sealing devices.