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

Abstract

The effects of frequency, volume fraction of carbon black, and porosity on the complex permittivity of the epoxy-carbon black composites were investigated and the frequency dispersion behavior model for the complex permittivity was proposed. In the epoxy-carbon black composites, the frequency dispersion behaviors of the complex permittivity changed from relaxation spectrum to resonance spectrum with increasing the amount of carbon black. The complex permittivity of the composites increased with decreasing the porosity. Comparing the complex permittivity of the composites filled with 2 vol % of carbon black with the values obtained from three types of previously reported model equations, the relaxation behavior coincided with the Havriliak-Negami model. The damping and asymmetrical factor values were increased with increasing porosity in the composites. The empirical equation proposed here was useful in describing the complex permittivity of the composites of >3 vol % carbon black with resonance type. The damping factor (γ) decreased as the filler content increased, but the asymmetrical factor (κ) increased reversely.