Peroxide Vulcanized EPDM Rubber/Polyhedral Oligomeric Silsesquioxane Nanocomposites: Vulcanization Behavior, Mechanical Properties, and Thermal Stability

Effects of two different polyhedral oligomeric silsesquioxane (POSS), an acrylisobutyl POSS (AIBuPOSS) containing an acrylate group along with seven isobutyl group on its cage and an octaisobutyl POSS where the acrylate group is absent, on vulcanization behavior, mechanical properties, and thermal stability of peroxide vulcanized ethylene-propylene-diene rubber (EPDM) were investigated. The POSS was incorporated into the EPDM by melt mixing with POSS content of 0-10 part per hundred of rubber (phr). Oscillating disk rheometer analysis revealed that the acrylate group of the POSS are activated by dicumyl peroxide and improves the peroxide crosslinking efficiency of EPDM rubber. Solid state Si-29-nuclear magnetic resonance spectroscopy analysis and field emission scanning electron microscopy with energy dispersive X-ray analysis of the EPDM/POSS vulcanizates showed that the AIBu-POSS are covalently grafted onto the EPDM chain during vulcanization and are dispersed uniformly at the nanometer scale in the rubber matrix. The EPDM/AIBuPOSS nanocomposites exhibit great improvement in tensile, tear strength, and modulus with a concurrent increase in elongation-at-break. Enhanced thermal stability in the nanocomposite was also observed. (C) 2015 Society of Plastics Engineers