PERCOLATION CONCEPT AND THE ELECTRICAL-CONDUCTIVITY OF CARBON BLACK-POLYMER COMPOSITES 3-CRYSTALLINE CHLOROPRENE RUBBER MIXED WITH FEF CARBON-BLACK

The filler concentration and temperature dependence of the electrical conductivity (sigma) of a crystalline chloroprene rubber (Butaclor 41H ) mixed with fast extrusion furnace (FEF) carbon black was investigate d. It was found that the percolation concept holds true for the compos ites where sigma shows a sharp increase when the mass fraction of FEF carbon black in the mixture exceeds 20%. The estimated values of the f illing factor (f) and the occupation number (Z) were found to be 0.82 and 8.2, respectively. The scaling law of the percolation clusters [si gma=sigma(0)(P-P-c)(beta)] was valid within the range P-c less than or equal to P less than or equal to 0.34 and the estimated value of beta was 6.8. The temperature dependence of sigma is thermally activated b elow and at the percolation threshold with the same activation energy. The decrease in sigma with temperature followed by a subsequent incre ase above a certain temperature was attributed to the phase transition of CR and the change in the size of carbon black clusters from infini te to finite with temperature. In highly loaded composites the tempera ture dependence of sigma is controlled by the breakdown and reformatio n of carbon clusters with temperature.