Earl Clark

Formation of High Impact Polystyrene from Blends of Polystyrene with Butadiene/Styrene Block Copolymers

Two processes have been described for preparing impact polystyrene, graft polymerization of rubber solutions in styrene(1,2,3) and mechanical mixing of polystyrene with rubber(4). In both processes, toughness results from formation of dispersed rubber particles which are crosslinked and adhere to the continuous polystyrene phase(5,6,7). Size of the rubber particles in the graft process is determined by intensity of agitation during precipitation of the rubber(3) while antioxidant content and mixing time control the rubber dispersion of blends(4). Predominance of the graft process(8) in current production of impact polystyrene results from more efficient use of rubber in producing toughness.