Acrylic Elastomers Preparation and Properties of Vulcanizable Acrylic Ester-Acrylonitrile Copolymers

Abstract Copolymers of various acrylic esters, from ethyl to octyl, with 5 to 15 per rent acrylonitrile or methacrylonitrile, were prepared by refluxing emulsion polymerization and in two instances by redox polymerization. These copolymers were easily vulcanized with sulfur and triethylene tetramine recipes. Heat-resistant vulcanizates were obtained from the copolymers of acrylonitrile with ethyl, butyl, amyl, and hexyl acrylates and also from the copolymer of methacrylonitrile with butyl acrylate. The octyl acrylate-acrylonitrile copolymers and the octyl acrylate, ethyl acrylate, and acrylonitrile terpolymerse did not show similar heat resistance. Terpolymers obtained from ethyl acrylate, butyl acrylate, and acrylonitrile, however, produced heat-resistant vulcanizates. The vulcanizates of lowest brittle points were obtained from copolymers of the higher acrylic esters, but regardless of the acrylic ester used, the brittle point was considerably increased with increasing acrylonitrile content of the copolymer. The copolymers from 95 per cent amyl acrylate—5 per cent acrylonitrile and the copolymer of 91 per cent hexyl acrylate—9 per cent acrylonitrile showed brittle points of −45° and −49° F, respectively. In general, the brittle point of heat-resistant stocks did not change by more than approximately 10° F on heat-aging for 72 hours at 350° F. The butyl acrylate-methacrylonitrile copolymer appeared to have somewhat better heat-aging properties than did the butyl acrylate-acrylonitrile copolymer.