Graft copolymerization of vinyl chloride onto ethylene propylene rubber (EPR) and ethylene propylenediene monomer (EPDM) by bulk process

Vinyl chloride was graft copolymerized on ethylene propylene rubber (EPR) and ethylene propylene diene‐monomer rubber (EPDM) by a bulk process to give a multi‐component end product consisting of three components and two phases. The reaction system forms a pseudo‐emulsion at an early stage of reaction where the phase morphology of graft poly(vinyl chloride) (PVC) is determined. The formation of pseudo‐emulsion was confirmed visually, by the particle size of PVC prepared in the presence of rubber and by the phase morphology of rub be r‐g‐PVC which is similar to that from an aqueous emulsion system. The degree of graft depends on the unsaturation of the rubber used as backbone. The amount of grafted EPR does not exceed 60 percent of the initial rubber; however, the amount of grafted EPDM is always higher than 60 percent of the initial rubber and increases further as the unsaturation increases. The degree of graft was found to be independent of the type of radical initiator used indicating that the abstraction of hydrogen from the rubber is carried out by the PVC radical to generate the grafting point. The graft PVC shows considerably improved processability which is equivalent to that of commercial vinyl chloride copolymers containing small amounts of propylene. It also shows dramatically improved impact strength which ranges from ten to twenty times that of PVC homopolymers.