PTC effect in carbon black-filled ethylene-propylene-diene terpolymer systems

The positive temperature coefficient (PTC) effects of carbon black (CB)-fil led semicrystalline and amorphous ethylene-propylene-diene terpolymer (EPDM ) composites were studied. The semicrystalline EPDM/CB composite exhibited a low PTC effect followed by a pronounced negative temperature coefficient (NTC) effect, while the amorphous EPDM/CB composite exhibited only an NTC e ffect. By the effect of gamma -ray irradiation, not only was the NTC effect of the composites eliminated, but also a high PTC effect appeared. The PTC intensity reached as high as six orders of magnitude even for an amorphous EPDM/CB composite and the PTC transition temperature decreased with the ir radiation dose. (C) 2001 John Wiley & Sons, Inc.