Enhancement of Mechanical Strength and Toughness of Ethylene-propylene-diene Rubber Using an Ethylene-based Ionomer

Ethylene-propylene-diene rubber (EPDM) has good heat, weathering and ozone resistance among general rubbers. Although tear strength of EPDM is not high, improvement of the strength enables expansion of applications of EPDM as a durable rubber. Poly(ethylene-co-methacrylic acid) ionomer (EMMA) is lightweight derived from low density polyethylene and shows high mechanical strength and toughness because of ionic crosslinking network composed of rigid ionic clusters. In this study, EMMA was blended with EPDM using general mixers so that mechanical strength and toughness of EPDM were enhanced simultaneously. Loading of EMMA increased not only hardness and tensile strength but also elongation at break. EPDM/EMMA blends with EMMA of 20 and 30 phr showed high tensile destructive energy and tear strength compared to equivalently hard EPDM with high amount of carbon black. Morphology of EPDM/EMMA blend was observed using a scanning probe microscope and EMMA dispersed in EPDM as islands of the sea-island structure. EPDM/EMMA blends showed healing function by heat pressing. Notches of EPDM/EMMA blend seats were healed at 150 °C or more. Healing efficiency of the specimens with EMMA of 30 phr after break in tensile and tear tests were about 15% and 30%, respectively.