Abstract
AbstractThe dielectric relaxation characteristics of microcellular EPDM vulcanizates has been studied as a function of variation in filler and blowing agent loadings in the frequency range of 100–106 Hz. The dielectric constant ε′ increases with increasing filler loadings at all frequencies. This has been explained on the basis of interfacial polarization of fillers in a heterogeneous medium. The effect of variation in filler and blowing agent loadings on the complex and real parts of impedance was distinctly visible. Which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. The phenomenon of percolation in the composites has been discussed based on the measured changes in electric conductivity and morphology of composites at different concentrations of the filler. The percolation threshold as studied by DC conductivity occurred near 40 phr of filler loading. SEM microphotographs showed agglomeration of the filler above this concentration and formation of a continuous network structure. POLYM. COMPOS., 28: 657–666, 2007. © 2007 Society of Plastics Engineers
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