Electrical response of microcellular EPDM rubber composites: complex dielectric modulus formalism and current–voltage characteristics

Abstract

Electrical response of conductive carbon black (Vulcan XC 72)-reinforced microcellular EPDM rubber composites has been studied as a function of variation in blowing agent and filler loading in the frequency range of 10–10⁵ Hz. The data was analyzed by dielectric modulus formalism. The examined system exhibit a strong dependence of dielectric modulus on the applied frequency. A gradual increase of real part of dielectric modulus with frequency is observed for all fillers and blowing agent loadings. The imaginary part of the dielectric modulus exhibited one relaxation peak with frequency at each filler and blowing agent loading. With increase in filler loading the peak shifts toward higher frequency whereas, with blowing agent loading the relaxation peak shifts toward lower frequency. The relationship between real and imaginary part of dielectric modulus shows a semicircular trend followed by a linear increase for all filler and blowing agent loadings. Hence, the presence of non-Debye type of relaxations has been confirmed. The effect of variations in filler and blowing agent loading on current–voltage characteristics has also been investigated. It is observed that with increase in filler and blowing agent loading, the nonlinearity of the curves increases and the point from which this nonlinearity starts decreases to lower voltage values. It is also observed that the electrical current is free from time when the measuring voltage is low. But as the applied voltage increase to 30 and 40 V, the electrical current changes with time.