Effect of thermal conductivity on tracking failure of Epoxy/BN composite under pulse strength

Epoxy (EX) is widely used as insulating materials in electric devices with its excellent insulating properties in spite of its weak ability of thermal conduction. One possible way to obtain high thermal conductivity for Epoxy is the use of an inorganic filling material. Tracking failure is a typical dielectric breakdown performance on polymer surface. Thermal conductivity is associated with the tracking failure performance. In this paper, it is attempted to clarify whether the addition of Boron Nitride (BN) particles can achieve the aim of improving resistance to tracking failure of Epoxy by the way of increasing its thermal conductivity. Prior to test, samples were prepared by dispersing BN particles into EX with shear force. Tracking failure tests were performed at room temperature. The thermal conductivity effects on the time to tracking failure, the discharge quantity of discharge current and the thermal photographs were discussed. Obtained results show that with increasing the concentration of BN particles, the maximum temperature and the discharge quantity decrease, but the time to tracking failure increases. The experimental results suggest that the concentration of BN particles plays a main role in the result of the tracking failure. The resistance to tracking is improved by the filler of BN particles, which is due to the improvement of thermal conductivity.