Abstract
Low density polyethylene (LDPE) is widely used as an electric insulating material in electric power cables. The generation of electrical treeing due to aging of LDPE may lose the reliability of its insulating capability. It is therefore important to suppress its treeing and to improve its electrical properties so that the reliability of cables can be improved. With this purpose, we prepared LDPE to which varius inorganic materials were added. Our investigation was particularly focused on lithium carbonate and quartz which were effective to suppress the treeing when added to LDPE. Lithium carbonate-added (0.25phr) showed in two hours of discharge the length of tree, 150μm shorter than that (560μm) of non-added LDPE, offering obvious suppressing effect on treeing generation. We found that this effect was more significant than quartz-added LDPE and even at elevated temperatures lithium carbonate added LDPE exhibited suppression of treeing. The thermal decomposition temperature at which lithium carbonate-added (1phr) LDPE loses 50% of its weight rose 100°C more than non-added LDPE and 60°C more than that of quartz-added LDPE, which evidenced improvement in heat resistance of LDPE.
