Fractal agglomerates and electrical conductivity in carbon black polymer composites

SEM micrographs of carbon black polymer composites have been analysed in te rms of their fractal geometry. Acetylene black/ethylene butylacrylate copol ymer samples have a fractal dimension of about 1.8 at low filler concentrat ions that increases to 2.1 at high concentrations. The numerical values ind icate a cross-over from diffusion limited cluster aggregation (DLCA) to rea ction limited cluster aggregation (RLCA). Furnace black/EPDM composites hav e a fractal dimension of 1.9 at low concentrations and of 2.4 at higher fil ler fraction. We believe that in this case the increase in fractal dimensio n is only apparent and due to interpenetration. Possible connections betwee n fractal. geometry (fractal dimension and correlation length) and electric al conductivity are discussed. No clear connection could be determined. (C) 2001 Elsevier Science Ltd. All rights reserved.