FREQUENCY DISPERSION CHARACTERISTICS OF THE COMPLEX PERMITTIVITY OF THE EPOXY-CARBON BLACK COMPOSITES

The effects of frequency, volume fraction of carbon black, and porosit y on the complex permittivity of the epoxy-carbon black composites wer e investigated and the frequency dispersion behavior model for the com plex 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 am ount of carbon black. The complex permittivity of the composites incre ased 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 dam ping and asymmetrical factor values were increased with increasing por osity in the composites. The empirical equation proposed here was usef ul in describing the complex permittivity of the composites of > 3 vol % carbon black with resonance type. The damping factor (gamma) decrea sed as the filler content increased, but the asymmetrical factor (kapp a) increased reversely. (C) 1998 John Wiley & Sons, Inc.