Effects of oxidation and antioxidants on space charge in polyethylene

Space charge and conduction current in low-density polyethylene (LDPE) and antioxidants doped LDPE have been measured. They strongly depended upon oxidation and antioxidants. In LDPE, oxidation enhanced electron injection and, as a result, negative homo space charge near the cathode. In antioxidants doped LDPE, on the other hand, both positive and negative space charges increased with oxidation and then saturated. The conduction current in doped LDPE increased with oxidation in the low oxidation region, decreased in the intermediate oxidation region and increased again in the high oxidation region. These behaviors can be explained by the enhancement of both electron and hole injection due to oxidized antioxidants and the suppression of the current by carrier traps due to oxidation products in the PE bulk.