EFFECT OF DOSE-RATE ON EMULSION AND MICROEMULSION POLYMERIZATION OF STYRENE

Emulsion and microemulsion polymerization of styrene were initiated wi th a gamma ray to study the effect of dose rate on polymerization. In both systems, there is an apparent plateau of polymerization rate in t he curve of reaction rate vs. conversion. It was shown that emulsion p olymerization conformed to the Smith-Ewart theory very well. Changing the dose rate in interval 2 had no great influence on polymerization r ate, but it changed the average lifetime of radicals in polymer partic les and affected the molecular weight of polymer produced. For microem ulsion polymerization it was assumed that in the plateau it is the num ber of growing polymer particles being kept constant, not the number o f polymer particles. When the dose rate was changed while the polymeri zation came into the constant period, the polymerization rate and the molecular weight of the polymer varied with the dose rate. (C) 1998 Jo hn Wiley & Sons, Inc.