The complex permittivity of carbon black/epoxy composites containing
different amounts of conductive carbon black particles was reported in the
frequency range 100 Hz–15 MHz and over the temperature range 23–80 °C. The shape of experimental spectra of these heterogeneous media gives
evidence of a typical dielectric relaxation process below the threshold
percolation. The temperature dependence of the dielectric response has been
analysed below and at near the epoxy glass transition temperature (T
≅ 80 °C), for various carbon concentrations. Jonscher's
phenomenological model has been used for modelling this relaxation process.
The activation energy, deduced from Arrhenius equation, is found to be
insensitive to the carbon black concentration. This behavior is discussed in
term of the interfacial interaction between the carbon particles and the
polymer. Besides, the increase of both parts of the complex permittivity
with increasing the carbon black concentration and the temperature is
compared to the recently proposed Shin's mixture law.