A Novel Approach to Investigating Effect of Sulfur as a Coagent on the Quasi‐Static and Cyclic–Dynamic Fatigue Properties of Peroxide Cured EPDM

The effect of sulfur on the quasi-static and cyclic-dynamic fatigue properties of ethylene propylene diene monomer (EPDM) after three fatigue cycles were investigated under two specially designed test programs. The results turned out that sulfur as a coagent slowed down the vulcanization rate of EPDM compounds and reduced the chemical crosslinks. Further study on the effect of sulfur on the crosslinking behavior showed that this effect could be quantitatively described in linearity and became more distinct at higher crosslinking density. The addition of sulfur as a coagent improved the tearing performance of EPDM as a result of newly generated polysulfur bonds (-S-x-). The strain and frequency sweep procedures were designed to study the dynamic rheological behavior and we obtained that the storage modulus of EPDM depended less on the addition of sulfur as well as sweeping temperature in sulfur-assisted curing system. The changes of loss factors obtained from the two sweep procedures were employed to survey the dynamic fatigue properties of EPDM, indicating that the fatigue behavior depended more on peroxide dosage than sulfur content, which might be due to the smaller proportion of polysulfur bridges in the final crosslinking structures of EPDM. POLYM. ENG. SCI., 2019. (c) 2019 Society of Plastics Engineers