Model simulation studies of complex free radical reactions: The graft copolymerization of styrene and acrylonitrile onto ethylene‐propylene‐isopropylidendicyclopentadiene terpolymer

Abstract

A kinetic analysis without steady approximation of the graft copolymerization of styrene‐acrylonitrile onto ethylene‐ propylene‐isopropylidendicyclopentadiene terpolymer (EP‐IPDCP) is described. Some of the kinetic constants were experimentally determined. The grafting process is interpreted mainly in terms of the attack on EP‐IPDCP by benzoyloxy radicals; phenyl radicals play a minor negative role by enhancing the rate of homopolymerization. A major contribution to the grafting yield is made by the propagation steps in graft polymerization and by crossed termination between grafted and ungrafted chains; of minor importance are the cross terminations between ungrafted growing chains and rubber radicals. The ole played by the solvent (benzene) and by saturated and unsaturated units in the EP‐IPDCP chains is analyzed. Diffusion effects caused by the poor solvent compatibility of grafted and ungrafted chains were taken into account by allowing the termination and propagation rate constants to change in a controlled way during the reaction. The trapping of EP‐IPDCP units caused by the aggregation of polymer particles seems to be indispensable to explain the decreasing trend of the grafting efficiency curve. Other information of interest pertains to the distribution of initiating radicals among the various competing reactions in the process and to the data of concentrations versus reaction time for reactants, products, and free radical intermediates. The results of a sensitivity analysis and the rate constants used in the calculations are given.

Synthesis of high rubber styrene–EPDM–acrylonitrile graft copolymer and its toughening effect on SAN

“…This result can be explained as follows: the viscosity of the reaction mass increases as EPDM content increases and, as a result, the diffusion of monomer into EPDM molecules becomes difficult and the monomer tends to copolymerization. According to Faucitano,9 the mechanism of the grafting process, of styrene–acrylonitrile onto EPDM, was that the benzoyloxy radicals attack EPDM first and then induce the graft polymerization of monomers. Consequently it can be concluded that, when a higher concentration of EPDM is charged, a higher ratio of formation rate of EPDM macromolecules radicals to monomer radicals results and then will cause a higher grafting efficiency.…”