Studies on polymer blends. III. Butadiene–acrylonitrile copolymer and polybutadiene–polyacrylonitrile blend

Abstract The properties of butadiene–acrylonitrile copolymers were compared with those of polybutadiene–polyacrylonitrile blends. Also, the properties of copolymers having an acrylonitrile unit content of about 30% were compared with those of polymer blends having the same acrylonitrile unit content, i.e., NBR–NBR, polybutadiene–NBR, and polyacrylonitrile–NBR, having different acrylonitrile unit contents. These blends were prepared by roll blending and the vulcanizates were prepared by sulfur cure. The properties of the copolymers were markedly different from those of the blends, that is, in the blends the properties showed a linear relationship with their blending ratios, while in the copolymers the properties showed a curvilinear relationship. In the cases of the polymer blends having a constant acrylonitrile unit content, those blends which were prepared by blending two polymers having similar acrylonitrile unit contents showed better properties than the ones having very different acrylonitrile unit contents.