Electrical and mechanical properties of acrylonitrile rubber and linear low density polyethylene composites in the vicinity of the percolation threshold

The electrical and mechanical properties of acrylonitrile rubber (NBR), linear low density polyethylene (LLDPE) and NBR/LLDPE blends 50/50 with different compositions were studied before and after the addition of high abrasion furnace black (HAF) with different content of high abrasion furnace black (HAF) with different concentrations in order to find out the percolation thresholds in relation to the net work formation. After certain concentration of HAF (30 phr for NBR and 10 phr for both LLDPE and the blend 50/50) an abrupt increase in the electrical conductivity σ was noticed. With this increase, the tendency of the conductive chain formation increases through the aggregation of the carbon black particles network. This result was supported by the dielectric data (permittivity ε′ and dielectric loss ε″) in addition to the relaxation time obtained from the analysis of the absorption curves relating ε″ and frequency using suitable functions. The mechanical properties which investigated through the measurements of tensile and elongation at yield and rupture indicate an abrupt increase at the same concentration of HAF found in the case of electrical measurements. This result gives evidence to the good applicability between both mechanical and electrical investigations through the network formations. Any how, the percolation threshold found in case of NBR/LLDPE blend is less than that for NBR itself. This result is attributed to the uneven distribution of the filler in the incompatible blend matrix.