Effect of antioxidants on pre-crosslinking and DC breakdown characteristics of XLPE cable insulation

Pre-crosslinking is likely to occur during the extrusion process of cross-linked polyethylene (XLPE) used for high voltage cables, which has negative effects on the extrusion molding of XLPE insulation. Adding antioxidants contributes to delaying the pre-crosslinking, so different insulating materials with three kinds of isomers of hindered phenolic antioxidants are investigated, respectively. The experimental results show that the insulating materials added with antioxidant 736 has a better effect on delaying pre-crosslinking, but its final cross-linking degree is lower. Bond dissociation energy (BDE) and energy band distribution of different antioxidant molecules were obtained by first-principles calculation. Besides, AO736 has lower BDE compared with AO2246-S and AO300, which reflects better free radical eliminating and delaying pre-crosslinking abilities. What is more, AO736 can produces deep hole traps, which enhances the ability to capture carriers, thereby reducing its average free path and weakening the damage of collision ionization to molecular chains. So it can significantly improve DC breakdown strength of XLPE. This study shows that AO736 has potential application prospect in XLPE insulating materials.