Secondary phase inversion induced by addition of polystyrene during prepolymerization of high impact polystyrene in a batch reactor

Abstract

High-impact polystyrenes (HIPS) which have quasi-bimodal polybutadiene (PBD) particle size distribution were obtained by the addition of polystyrene (PS) pellets shortly after phase inversion. The PBD particle size distribution of these HIPS deviated from the usual Gaussian distribution on a logarithmic scale of PBD particle diameter, especially in the region of small particle sizes. The residual PBD appeared to be separated from the PS phase by the addition of PS pellets, and this second minor phase inversion produced the smaller PBD particles. This postulate could be confirmed by measuring the apparent viscosity of the system during prepolymerization. The Izod impact strength and the gloss of these HIPS, polymerized by this new technique, were greater than those of the normal HIPS, and were found to be consistent with previous results on the bimodal HIPS that were made by blending small PBD particle size HIPS with large PBD particle size HIPS. (C) 1996 John Wiley & Sons, Inc.