Observed anisotropy in the electrical conductivity of carbon black/polyethylene composites

The anisotropic electrical behavior of low density polyethylene/carbon black composites was studied as a function of temperature and filler concentration. It was found that the electrical conductivity of the composites has a percolating behavior. An abrupt change in the conductivity at 413K was observed for ail composites of carbon black content 10, 15 and 20wt.%. This inflection presents slopes of opposite signs and locates at a unique temperature (413) for all composites. The reversed behavior of conductivity versus temperature indicates that the charge carriers have two different mobilities and different activation energies due to some effects that change with composites structure such as morphology, crystallinity, phase transformation, path orientation, and viscosity with increasing temperature. At high temperature range the increase in the electrical conductivity may be mainly attributed to ionic conduction mechanisms.