Electrical conductivity and electric modulus of stable Kevlar® fiber loaded HAF/NBR rubber composite

DC, AC conductivities and dielectric properties of high abrasion furnace carbon black (HAF)/acrylonitrile butadiene rubber (NBR) composite have been studied with varying the aramide Stable Kevlar(R) fiber content, temperature, and frequency. Generally, the electrical conductivity was decreased with increasing Stable Kevlar(R) fiber content, which was confirmed by the positron annihilation lifetime spectroscopy. Negative temperature coefficient of conductivity (NTCC) behavior between 353 and 413 K was detected, except for the composite containing 10 phr Kevlar which showed positive temperature coefficient of conductivity (PTCC) behavior above 383 K. These NTCC and PTCC behaviors were further manifested by differential scanning calorimetry (DSC). For the composite with 10 phr Kevlar, the interfacial polarization between the fibers and the polymeric composite can be ascribed to Maxwell-Wagner-Sillars mechanism. The (MWS) relaxation disappeared for higher fibers content. The analysis of the electric modulus in the frequency range from 1 kHz to 1 MHz shows that the interfacial relaxation obeys ColeDavison distribution of relaxation times. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012