The influence of modest quantities of carbon black on electrical and mechanical properties of cross-linked EPR rubber

The influence of carbon black on the electrical and mechanical behavior of an EPDM (ethylene-propylene diene monomer) rubber was investigated. Resistivity, dissipation factor, dielectric strength, and initial tracking voltage, as well as hardness, tensile strength, elongation, and some moduli, were measured on the EPDM test samples filled with amounts of carbon black ranging from 0% to about 15% in mass. The existence of a critical threshold of carbon black mass fraction that makes the rubber conductive was found. The possibility of improving the mechanical behavior of EPDM rubber for electrical applications by filling it with a small quantity of carbon black was shown. Greater improvements of mechanical properties were accompanied by a degradation of electrical properties as the mass fraction of carbon black increased