Design of Polyimide-Based Composite Insulating Paper with High Corona Life Resistance

The corona resistance of insulating materials is a critical factor determining the service life of motors. This study prepared a composite insulating paper by cospinning polyimide (PI) with bismaleimide-diallyl bisphenol A/aluminum dihydrogen phosphate (BD-A), exhibiting notably enhanced corona resistance in comparison to pure PI insulating paper. For instance, the PI/100 wt % BD-A composite (mass ratio of PI to BD-A of 1:1) exhibited a corona resistance exceeding 703 h under test conditions of 20 kHz symmetric pulsed square wave with a 2 kV peak-to-peak voltage and 100 ns rise time, substantially surpassing the pure PI insulating paper’s corona resistance of approximately 0.5 h. The incorporation of an appropriate amount of aluminum dihydrogen phosphate (ADP) markedly enhanced the material’s corona resistance, electrical properties, and thermal stability. This improvement can be attributed to ADP’s ability to create specific trap energy levels that capture carriers, thereby inhibiting their migration. Furthermore, ADP optimized the microstructure of the composite insulating paper and modified energy transfer pathways, enhancing the scattering and absorption of electrons at the avalanche front. These mechanisms synergistically contributed to the enhanced corona resistance of the material. This research provides a viable solution for high-voltage motor insulation and advances the development of high-performance motors.