Investigation of Network Structure and Dynamic Mechanical Properties of Peroxide-Cured Ethylene Propylene Diene Rubber

The effect of peroxide and co-agent amount on the cure behavior, network structure, and dynamic mechanical properties of ethylene-propylene elastomers were studied by moving die rheometer, equilibrium swelling and dynamical mechanical measurements. The increase in peroxide and co-agent concentrations resulted in an increase in total cross-link density, Ctot. The model calculation results based on torque measurements considered the changes in Ctot as a function of peroxide and co-agent content; it linearly depended on initial peroxide content when the co-agent content was constant. The torque measurements were also carried out to investigate the cross-linking efficiencies of the peroxide and the co-agent triallyl isocyanurate (TAIC); the efficiencies were evaluated as 77–95% and 33%, respectively, but the use of TAIC didn't affect the scorch time and rate constants of EPDM compounds significantly. The incorporation of TAIC into the network enhanced the network heterogeneity, the glass transition temperature shifted towards higher temperature and the peak values of the loss factor gradually decreased, both of which were caused by restricted segmental mobility due to the increase in cross-link density.