The effects of oxidation on the electrical conduction of polyethylene

The effects of oxidation on the electrical conduction of low- and high-density polyethylene (LD-PE and HD-PE) have been studied. It has been found that oxidation enhances the carrier mobility in LD-PE, but lowers that in HD-PE. A qualitative explanation of these opposing effects is given, based on the assumption that carbonyl groups introduced in the amorphous regions of PE act as hopping centres, whereas oxidation products introduced in the crystalline surface regions become deep traps. The existence of hopping centres and deep traps in oxidised PE is confirmed by the TSC experiments. Since HD-PE has a high degree of crystallinity, carriers injected into HD-PE must move across crystalline regions to the counter-electrode. So the deep traps in the crystalline surface regions can effectively reduce the carrier mobility in HD-PE.