Study On Effect Of Oil On Peroxide Curing Efficiency Of EPDM

In this paper, the effects of oil on cure character, dynamic performance, crosslink density and cure kinetics of peroxide curing EPDM were investigated, based on EPDM Keltan 7450 of Lanxess.The result showed that with content of oil increased, the minimum torque and maximum torque of EPDM were gradually reduced, while the scorch time and cure time were both extended, except that cure time reduced with 10phr oil.The result of frequency dependence of dynamic property showed that for EPDM compounds, due to the softening effect of oil, storage modulus reduced with content of oil. While, loss factor increased for the relative slip of rubber molecular chains increased with content of oil. For cured EPDM, storage modulus increased and the frequency dependence was reduced with content of peroxide; Loss factor of cured EPDM decreased for cross-linked network was more perfect with content of peroxide; storage modulus decreased and loss factor increased with content of oil increased.Compared with crosslink density measured by equilibrium swelling method and MDR method, the result showed that it was feasible to calculate crosslink density according to MDR method for peroxide cured EPDM extended with oil or not.Crosslink density of cured EPDM was calculated through cure curves measured by MDR. The result showed that crosslink density gradually decreased with content of paraffinic oil. Oil could consume part of free radicals decomposed from peroxide, leading to peroxide cure efficiency (PCE) decreased. Compared peroxide cure and sulfur vulcanization, crosslink density of EPDM decreased with content of paraffinic oil. But for peroxide cure, oil had a more significant influence on crosslink density. The similar tendency of crosslink density was found with squalane or decalin instead of paraffinic oil, but the effect of paraffinic oil on PCE was larger.Cure kinetics of peroxide curing EPDM was studied according to cure curves measured by MDR at different temperatures. The result showed that peroxide cure reaction was a first order reaction. Cure rate constant k increased with content of peroxide, while k increased at an elevated cure temperature. Activation energy of cure reaction showed an increasing trend with content of peroxide.When oil added, peroxide cure reaction remained a first order reaction. Cure rate constant k and reaction activation energy decreased with content of paraffinic oil. Cure reaction rate constant increased firstly then decreased when squalane or decalin instead of paraffinic oil respectively.Kissinger method was used to calculate the kinetic parameters of the cure reaction of virgin EPDM and oil extended EPDM through DSC. Kinetic parameters of cure reaction were similar to those measured by MDR.