Time Evolution of Rubber Particle Size Distribution in Bulk Polymerization of High Impact Polystyrene

Abstract

High impact polystyrene has been a typical thermoplastic to improve the impact strength and toughness of polystyrene. One of the main factors affecting these properties is the particle size and size distribution of the rubber phase. The rubber-phase particle size is related to the prepolymerization time that is determined by the phase inversion between polystyrene and rubber phases. However, the phase inversion in highly viscous oil-in-oil emulsions proceeds with a transitional fashion, not a catastrophic inversion. It has been tried to elucidate this inversion point by using viscosity, conversion and conductivity measurement techniques. They are used to find the point of phase inversion, indicative of the end of phase inversion, but they cannot produce its progression consecutively. In this study, a laser light scattering technique is utilized to characterize the evolution of the rubber particle size distribution depending on reaction time as well as to find the point of phase inversion. The progression of phase inversion during polymerization is monitored by this technique, which in turn is used to establish the proper prepolymerization time. Comparisons, limitations, and applications are dealt with.