Conductive rubber composites from different blends of ethylene-propylene-diene rubber and nitrile rubber

Conductive rubber composites were derived from different blends of ethylene-propylene-diene monomer (EPDM) rubber and acrylonitrile butadiene rubber (NBR) containing acetylene black. The electrical and mechanical properties of these composites were measured. The percolation limit for achieving high conductivity of conductive filler depends on the viscosity of the blend. The higher the viscosity, the higher is the percolation limit. The conductivity rises with increasing temperature, and the activation energy of conduction increases with the decrease in the loading of conductive filler and percentage of NBR in the blend. Electrical hysteresis and an electrical resistivity difference during the heating-cooling cycle are observed for these systems, which is mainly due to some kind of irreversible change occurring in the conductive networks during heating. The mechanisms of conduction of these systems were discussed in the light of different theories. It was found that the degree of reinforcement by acetylene black in blends compares with those in the pure components NBR and EPDM. This is due to incompatibility of two elastomers in the blend.