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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.

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Tricyclo[5.2.1.0]deca-2,5,8-triene (1) or a mixture of its methyl derivatives was used as termonomer to obtain ethylene—propylene—triene terpolymers (EPTM) having unusual properties in the curing process, even at low levels of triene (ca. 1 wt %). Three types of catalyst systems have been investigated, based on VCl4, VO[O(CH2)3CH3]3, or V(acac)3 and (C2H5)2AlCl. Several parameters of the terpolymerization process were studied (e.g. Al/V mole ratio; catalyst and termonomer concentration; polymerization time; presence of a Lewis base or chain transfer agent) and their influence on Mv and EPTM composition were evaluated. Fractionation data and the use of model compounds allow to conclude that 1 enters EPTM chains randomly and by selective opening of the norbornenic double bond, whereas the conjugated diene system is involved in side reactions if the catalyst has some acid character or the concentration of the triene is above some critical value.