CARBON-FIBER FILLED CONDUCTIVE COMPOSITES BASED ON NITRILE RUBBER (NBR), ETHYLENE-PROPYLENE DIENE RUBBER (EPDM) AND THEIR BLEND

The conductivity of nitrile rubber (NBR), ethylene-propylene -diene ru bber (EPDM) and 50/50 NBR/EPDM blend has been measured against the loa ding of conductive carbon fibre to check the percolation limit for eac h system. The volume resistivity of all fibre-rubber composites increa ses with the increase in temperature, and the rate of increase in resi stivity against temperature depends on the loading of carbon fibre and the nature of the base polymer. The change in volume resistivity duri ng the heating and cooling cycle does not follow the same route, leadi ng to the phenomena of electrical hysteresis and electrical set. The c urrent-voltage relation is linear at room temperature, but becomes non linear at higher temperature. Some mechanical properties of these comp osites are also measured. The applicability of different theoretical m odels to predict the modulus and conductivity of these systems has bee n tested. Deviations between theoretical and experimental values are a lso discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.