Polyamideimide-alumina nanocomposites for high-temperatures

Metal oxide nanoparticles have been shown to improve the dielectric breakdown strength of insulating polymers. Polyamideimide is a material of practical use for high temperature insulation, and nanoparticle fillers show promise in improving the high temperature stability and dielectric breakdown strength. This work demonstrates the effect of 40-50 nm alumina nanoparticles on the improvement in AC breakdown strength of polyamideimide at elevated temperature and characterizes related electrical properties to gain insight into the mechanisms leading to this improvement. Breakdown tests were performed at temperatures up to 300°C. The buildup and movement of space charge as a function of filler loading was measured at room temperature using pulsed electroacoustic analysis. Dielectric spectroscopy was used to measure the permittivity at temperatures up to 300°C. In addition to improving the dielectric breakdown strength, alumina nanoparticles also improved the resistance to thermal degradation, which should allow operation of the composites at temperatures above the operating temperature of the base resin.