Excellent mechanical performance and long-term heat resistance have been key requirements for many automotive under-the-hood applications. The continuous upper temperature resistance (CUTR) of a thermoset EPDM rubber is defined as the upper temperature limit of the thermal aging condition at which a thermoset compound retains at least 50 percent of original elongation and 80 percent tensile at break after 1,008 hours of heat aging (per Mercedes-Benz Supply Specification of Textile-reinforced coolant hoses-DBL 6254).
It is a challenging task for many of the thermoset EPDM rubber product manufacturers to meet the continuing increase in CUTR requirements and other more stringent design criteria for auto parts, such as under-the-hood coolant hose, wire and cable, and others.
In this paper the heat aging properties of vulcanized EPDM compounds were systematically studied. The EPDM thermal oxidation/degradation mechanism was proposed and discussed. In addition, the effects of EPDM molecular architecture, antioxidants and EPDM compound formulations on long-term heat aging properties were investigated. Finally, a superior high heat resistant EPDM solution had been successfully developed for automotive coolant hose applications to provide optimized product performance before and after long-term heat aging.