Effect of zinc chloride on polymerisations initiated by benzoyl peroxide

Abstract

Experiments were performed at 60°C with styrene and methyl methacrylate as monomers, methylethyl ketone as diluent and benzoyl peroxide as initiator. Introduction of zinc chloride caused an increase in the rate of polymerisation and a decrease in the molecular weight of the resulting polymer. End-group analyses showed that the additive produced an increase in the rate of initiation and in the ratio of benzoyloxy to phenyl end-groups and a decrease in the average number of initiator fragments per polymer molecule. In the absence of monomer, zinc chloride caused an induced decomposition of the peroxide in methylethyl ketone. The results are interpreted in terms of the modification of reactivities of radicals and molecules by complexing with zinc chloride.