RADIATION-INDUCED GRAFT POLYMERIZATION

Abstract

This chapter describes the synthesis of graft copolymers by radiation-induced graft polymerization. Copolymers are polymeric substances containing two or more units of two different polymeric species combined in some sequence. There are several experimental techniques one may employ to carry out the graft polymerization reaction. A variety of grafted polymers have been synthesized by radiation-induced graft polymerization. The course of radiation-induced graft polymerization is quite markedly affected by the presence of various additives. These fall into two classes, those that accelerate the rate of grafting and those that decelerate the rate of grafting. Additives that decelerate the grafting reaction include free radical inhibitors and retarders, chain transfer agents, and aromatic compounds. The practical aspect of graft polymerization lies in its utility in the modification of polymeric materials. Styrene grafts onto polyethylene show lowered tensile strengths and ultimate elongation, and increased elastic moduli and melt viscosity compared to ungrafted polyethylene. Grafting of styrene, methyl methacrylate, and styrene-acrylonitrile to natural rubber results in increased tensile strength and decreased elongation.