AC Brealdown Studies on Crosslinked EPDM

Using a spring-loaded needle against a plane electrode, ac breakdown studies have been made on a crosslinked Ethylene Propylene Diene terpolymer (EPDM) gum at varying electrode separations and crosslink densities. Critical breakdown strength of 3.5 MV/cm at room temperature and 9.0 MV/cm at -60°C were obtained. These values are independent of the crosslink densities of the rubber. The breakdown strength of EPDM is very close to that measured on polypropylene (6.0 MV/cm) and low density polyethylene (5.5 MV/cm) at room temperature.