Dielectric and structural properties of polymer carbon-black composites

Dielectric and structural properties of composite materials prepared by incorporating carbon black particles into a polymer matrix were investigated. Two types of carbon blacks, having very different structures of carbon black aggregates, were used. The composites were characterized in terms of their EPR (electron paramagnetic resonance) response, swelling and frequency variation of permittivity. The most notable feature of the analysis of the EPR signals is that we find a correlation of the percolation threshold concentration which is detected from the dc electrical conductivity with moments of the EPR lines. The role of the specific surface of carbon blacks is further analyzed. The paper also reports on the spectral response of the permittivity of these composite materials in the GHz frequency range