Study on corona-resistance of the polyimide/nano-TiO₂ hybrid films

Polyimide/nano-TiO₂ (PI/TiO₂) hybrid films were fabricated via in-situ dispersive polymerization and corona-resistance of films was studied. The trap state and ultraviolet absorption spectra of the films were measured by photon-stimulated discharge (PSD) and ultraviolet spectrophotometer. The surface morphology and fractal characteristics of the films were also analyzed by SEM and small angle X-ray scattering (SAXS). The results show that the trap density and mass fractal dimensions of hybrid films increase as TiO₂ is filled into PI. Meanwhile, surface fractal appears at 5% doping. The variation of fractal characteristics proves hybrid films with more compact and complex structure. With the TiO₂ doping concentration increasing, the time-to-breakdown of the hybrid films can be lengthened from 3.9h (0%) to 49h (7%), and ultraviolet absorptive capacity is improved. With the corona ageing continuing, PI matrix on the surface of films decomposes. Then, a large number of TiO₂ particles are gradually accumulated and play a role in shielding further erosion. The corona-resistance of hybrid films is enhanced by synergistic effects which are composed of trap state in the interface, TiO₂ particles properties and film fractal characteristics.