Morphology and Physico-Mechanical Properties of Closed Cell Microcellular EPDM Rubber Vulcanizates: Effect of Conductive Carbon Black and Blowing Agent

The morphology of the composite based on a new controlled long chain branching grade, oil extended EPDM (Keltan 7341A) and highly conductive carbon black (vulcanXC72) filled compound has been studied from SEM photomicrographs with variation of blowing agent and conductive carbon black filler loading. The average cell size, maximum cell size and cell density varies with variation of blowing agent and filler loading. Physical properties like relative density, hardness, tensile strength, modulus, tear strength decreases with blowing agent concentration. Enclosed gas pressure in a closed cell increases relative modulus at higher strain. Elongation at break decreases with blowing agent loading at higher filler loading. At lower filler loading it increases both with filler and blowing agent loading. The elastic nature of closed cells reduces the hysteresis loss compared to solid compounds. The stress relaxation behavior is independent of blowing agent loading.