Origin and Early Development of Rubber-Toughened Plastics

The use of brittle polymers, such as polyvinyl chloride (PVC) and polystyrene (PS), was limited prior to the development of rubber-toughened polymers in the 1930s and 1940s. PVC has been toughened by the addition of small amounts of acrylonitrile rubber (NBR) and other elastomeric materials. Over 1.5 million tons of rubber-toughened PVC is produced annually in the United States. The preferred toughening additive for PS is a styrene-butadiene rubber (SBR). Copolymers of styrene, such as styrene-acrylonitrile and styrene-maleic anhydride, have been toughened by the addition of NBR. The low-temperature resistance of these composites has been improved by grafting the polymers onto the elastomer. PS is also toughened by the addition of styrene-butadiene block copolymers. The art of toughening plastics by the addition of elastomers has been extended to include acrylics, polyolefins, polyesters, acetals, nylon, and thermosets. The impact resistance of epoxy resins has been enhanced by the addition of acrylonitrile-butadiene elastomeric copolymers.