Comparison of space charge behavior between polypropylene and polyethylene

In this paper we investigated space charge and electrical conduction in polypropylene (PP), H-PP and M-PP which are homopolymer and copolymer with 3∼3.5 % ethylene, respectively. Both space charge distribution and charging current were affected by the copolymerization of ethylene which enhanced electrical conduction. The amount of space charge in Al/PP/SC was the largest around 40 °C. The charge carriers injected from the semiconducting (SC) electrode became dominant with increasing temperature. Their results were compared with those of low-density polyethylene (LDPE). LDPE showed much higher current than PP. The difference in space charge distribution among H-PP, M-PP and LDPE was explained in terms of mobilities of charge carriers. The field dependence of charging currents was explained by Schottky injection.