Study on Electrical and Thermal Properties and Corona Resistance of Electric Field-Oriented MXene/PI Composite Films

Abstract Polyimide insulation films in variable-frequency motors frequently suffer from premature failure owing to insufficient corona resistance. In this study, two-dimensional MXene nanosheets with high in-plane electrical and thermal conductivity and structural anisotropy were selected. The in-situ polymerization method was utilized to prepare undoped and doped composite films at mass fractions of 1%, 3% and 5%, and a 100 V/mm DC electric field alignment technique was applied to fabricate oriented MXene/PI composite films with identical doping conditions. The properties of the fabricated composites were characterized by SEM, XRD, and TG. Furthermore, electrical and thermal parameters, including electrical conductivity, thermal conductivity, trap distribution, and corona resistance lifetime, were systematically measured. The experimental results indicated that the corona resistance lifetime increased with higher MXene loading. Notably, the performance was further enhanced by electric field alignment: the oriented 5 wt% MXene/PI composite exhibited a 46.6% improvement over the unoriented counterpart, and a 15-fold increase compared to undoped PI. Fitting results based on the Lewis-Nielsen model utilizing electrical and thermal conductivity data revealed a significantly increased shape factor A for the oriented samples. This increase corresponds to a higher effective aspect ratio, confirming that the DC electric field torque and dipole interactions effectively along the electric field direction. The incorporation of MXene enhances the electrothermal properties of composite films, while the electric field orientation further constructs an anisotropic electrical and thermal transport pathway, which facilitates carrier detrapping, thereby effectively disrupting the vicious cycle of “charge accumulation-field distortion-localized overheating”.