Insulating properties of polypropylene films coated with polyvinyl alcohol/aluminum nitride composite

Polypropylene (PP) dielectrics are core components of most film capacitors, and their insulating properties have a major impact on the storage density and safe and reliable operation of these capacitors. To further improve the insulating properties of PP films, we use a composite coating consisting of aluminum nitride particles and polyvinyl alcohol, providing a wide bandgap and high dielectric constant. The composite is applied to the surface of hot-pressed PP films to increase the bandgap width on the film surface. Experimental results show that when the AlN particle concentration is 3.5 wt% and the PVA concentration is 5 wt%, the composite film achieves its optimal breakdown field strength and flashover voltage, increasing by 5.21 and 20.15%, respectively, compared to the base film. Compared to the PP film, the coated film also reduces leakage current by approximately 61.62%, demonstrating a superior charge injection suppression effect. Tests including ultraviolet–visible absorption spectroscopy, leakage current measurement, and surface charge dissipation show that the developed composite coating helps increase the film surface bandgap and introduce shallow traps. Particles are assembled on the surface of hot-pressed isotropic PP films simply and easily, suggesting high production scalability for improving the insulating properties of PP dielectrics.