The effect of co-doped with nano- MgO and nano-TiO2 on breakdown strength and aging life of polyimide nanocomposites

As a high-temperature insulating material, polyimide is widely used in the inter-turn insulation of motors. In the actual working conditions, polyimide which works under long-term high-frequency square pulse wave, is prone to premature aging, and even breakdown. Most of the researchers investigated the polyimide polymer doped with single nanoparticles to improve its performance. However, the polyimide nanocomposite films doped with various nanoparticles has not been widely studied. In this paper, the polyimide nanocomposite films doped with surface modified nano-MgO and nano-TiO2were prepared by in-situ polymerization. Furthermore, the influence and mechanism of the doped nanoparticles was proposed based on the measurement of the breakdown strength and the corona aging life. The experimental results show that the polyimide nanocomposite films doped with nano-MgO and nano-TiO2 can improve the breakdown strength and the aging life simultaneously. This research has a practical significance on the modification of polyimide material.