The Conductivity, Distribution in Injection Moulded LDPE and HDPE Containing Carbon Black

Abstract

This study reports on the influence of processing on the electrical resistivity of injection moulded samples of LDPE and HDPE containing a conducting type of carbon black (CB). The resistivity was found to increase with orientation, the resistivity levels in the skin and shear layers being much higher than in the core. No simple correlation, however, could be found between the resistivity and the orientation at varying distance from the surface of the samples. LDPE was more sensitive to processing than HDPE. The skin and shear zones (high orientation) showed a marked frequency dependence (resistivity decreasing with frequency). The high resistivity values at the surface were reduced upon annealing. The effects observed can be interpreted qualitatively in terms of a CB-network disrupted during the flow of the melt; upon annealing a recovery of the network takes place (1).