Effect of thermal conductivity on tracking failure of Epoxy/Al2O3 nanocomposite under pulse strength

Polymeric insulating material is widely used for insulation in electric devices with its excellent insulating properties except a weakness of thermal conductivity. Tracking failure associated with the thermal conductivity is a typical dielectric breakdown performance on polymer surface. One possibility to change the resistance to tracking is the use of an inorganic filling material with high thermal conductivity. Therefore, it must be confirmed whether the filling material really improves the resistance to tracking by way of improving its thermal conductivity. In this paper, it is attempted to clarify whether the nano- Al203 particles achieve the aim of improving the resistance to tracking failure of Epoxy (EX) by the way of increasing the thermal conductivity. Prior to test, nano-Al203 particles were mixed into pure epoxy to obtain the epoxy/Al203 nanocomposites with the weight ratios of 0.5, 1, 2, 4 wt%, respectively. Tracking failure tests were independently performed at room temperature. The thermal conductivity effects with different concentration of Al203 particles on the time to tracking failure, the discharge quantity of discharge current and the thermal photographs were discussed. Obtained results indicate that with the concentration from a to 1 wt%, the time to tracking failure shows the increasing tendency and the max temperature and the discharge quantity show the decreasing tendency. But they show the opposite varying tendency with the concentration from 1 to 4 wt%. The experimental results suggest that the concentration of Al203 particles plays a main role in the result of the tracking failure, which is related to thermal conductivity reactions. The resistance to tracking can be improved by the filler of nano-Al203 particles which improves the thermal conductivity, especially mixed with the concentration of 1 wt%.