Percolation concept: Polymer-filler gel formation, electrical conductivity and dynamic electrical properties of carbon-black-filled rubbers

This paper reports results on comparison of polymer-filler gel formation measurements and electrical properties of carbon black filled styrene butadiene rubber (SBR) composites. Electrical conductivity (sigma) of compounds with different filler concentration has been measured, and dielectric constant (epsilon'), dielectric loss (epsilon '') and dissipation factor (tan delta) have been investigated at frequency range from 1 kHz to 13 MHz. It has been found that these systems follow percolation type model. Different electrical percolation thresholds of the composites have been found for different types of carbon black. Carbon blacks with the highest specific surface area reach the percolation threshold with the least fraction of carbon black loading. The electrical percolation threshold was found to be in a very good agreement with the filler concentration which is necessary for the coherent rubber-filler gel formation.