Impact Polystyrene: Factors Controlling the Rubber Efficiency

Abstract

Abstract The rubber phase volume (rubber + occluded polystyrene) can be widely varied in impact polystyrene by controlling the rate of agitation during polymerization. The tensile modulus and magnitude of the rubber phase mechanical loss transitions are related to the degree of polystyrene occlusion. It is shown that the occluded polystyrene can substitute for rubber in determining these parameters. Impact strength and ultimate elongation pass through maxima as the rubber phase volume is increased at constant rubber concentration due to the optimization of rubber phase volume with particle size and rubber phase modulus. Over crosslinking of the rubber and a high concentration of a low molecular weight tail of matrix polystyrene have deleterious effects on the impact strength and ultimate elongation. The optimization of these three factors is required in making efficient use of the rubber in impact polystyrene.