Water tree retardation of MgO/LDPE and MgO/XLPE nanocomposites

This paper deals with a water tree retardant characteristic of magnesium oxide (MgO) nano-filler addition to a low-density polyethylene (LDPE) and a cross-linked polyethylene (XLPE). Water tree retardation of both LDPE and XLPE at 313 K was improved with adding the MgO nano-filler at the content of more than 2 phr, while it was almost the same level at the nano-filler content of less than 2 phr. From the comparison of the result with MgO/XLPE and MgO/LDPE, the water tree retardation of MgO/XLPE was superior to that of MgO/LDPE at the nano-filler content of less than 2 phr, where MgO nano-filler shows no remarkable water tree retardant property. When the nano-filler content is 5 phr, however, water tree retardations of both XLPE and LDPE due to MgO addition became almost the same level and shows remarkable improvement with adding MgO nano-filler. As for the influence of temperature, the water tree at 333 K tends to grow faster and the retardation of water tree due to MgO addition became less effective than those at 313 K. Finally it was also found out that the growth rate of water tree became smaller with increasing MgO nano-fillers, showing the water tree retardant property of MgO nano-filler addition.