Resistor and dielectric properties of carbon‐black epoxy resin composites

Abstract

Abstract In this paper, the change in carbon black (CB) coherence with CB loading in CB resin composites has been studied from the viewpoint of resistance characteristics (resistivity, temperature coefficient of resistance) and dielectric properties by using HS 500 as CB. Equivalent circuit parameters ( R s , R c , and C c ) for these composites also are used for comparison. The dielectric properties have been obtained from a complex relative dielectric constant evaluated from the reflection and transmission coefficients at the frequency of 300 kHz to 3 GHz. The parameters for the equivalent circuit have been obtained from the frequency dependence of relative dielectric constant and the dc conductivity. As the CB loading increases, the dc resistivity decreases and R s and R c also decrease. This corresponds to the increase in the number of conductive paths formed by the CB structure bridging the electrodes. From the decrease of the positive TCR value, it is considered that a mechanically strong coherence was formed between the CB structure with an increase of the CB loading. Also, from the increase in the strength of relaxation and C c with the CB loading, the branching of the CB structure which branches out of the conduction path bridging the electrodes has been found to increase. In this case, a parameter β d which is a measure of the distribution of the relaxation time increased.