ELECTRICAL-CONDUCTIVITY OF THERMO-OXIDATIVELY-DEGRADED EPDM RUBBER

Oxidative degradation of rubbers, and the development of oxidized layers at the surfaces, results in increased electrical conductivity. This paper shows that for EPDM rubbers heavily oxidized at 200-degrees-C, the DC-conductivity increases more than two orders of magnitude, and the percolation threshold for DC conductivity is decreased below 5 phr carbon black. The effect of oxidation upon the electrical properties is explained as being due to the presence of polar groups, e.g., carbonyl groups. in between the carbon-black agglomerates which provide shorter distances for the electrons to tunnel through.