Frequency dispersion model of the complex permittivity of the epoxy-carbon black composites

The frequency dispersion behavior model for the complex permittivity of the epoxy-carbon black composites was investigated in terms of the relaxation type and resonance type, respectively. Comparing the complex permittivity values of the composites, filled with 2 vol% carbon black, that are obtained from three types of previously reported model equations, the relaxation behavior was found to be coincided with that obtained from the Havriliak-Negami model. The damping and asymmetrical factor values were increased with increasing porosity in the composite. The emperical equation proposed here is found to be very satisfactory in explaining the complex permittivity of the composites of more than 3 vol% carbon black with resonance type. It is also found that the damping factor (γ) and the asymmetrical factor (k) in this equation were dependent on the interface between the matrix and filler. It is found that the γ decreased as the filler content increased, but k increased reversely.