Plastics are a relatively new class of materials invented during the past century, mostly over the past 75 years. Here are examples of some common plastics still in use together with the years they were invented: Bakelite (phenolic), 1909; PVC (polyvinyl chloride), 1933; nylon, 1934; Plexiglas^® (polymethyl methacrylate), 1934; polystyrene, 1938; Teflon^® (polytetrafluoroethylene), 1938; Orlon^® (polyacrylonitrile), 1941; polyethylene, 1942; Araldite^® (epoxy) 1943, Dacron^® (poly(ethylene terephthalate)), 1953; polypropylene, 1954; PUR (polyurethane), 1954; Lexan™ (polycarbonate), 1955; Delrin^® (polyoxymethylene), 1959; Kapton^® (polyimide), 1961; Udel^® (polysulfone), 1965; Noryl™ (poly(phenylene oxide)), 1966; Ryton^® (poly(phenylene sulfide)), 1972; Kevlar^® (aramid fibers), 1972; Torlon^® (poly(amide-imide)), 1972; Ardel^® (polyarylate), 1978; Victrex™ (polyetheretherketone, or PEEK) 1979; and Ultem™ (polyetherimide), 1982.