Coating carbon fiber using polyimide–silica nanocomposite by electrophoretic deposition

Polyamic acid–silica hybrid colloidal emulsion with an average particle size of 200 nm was prepared by dispersing nano-silica into polyamic acid colloidal particles. The polyimide–silica hybrid nanocomposite coating was fabricated onto carbon fiber through electrophoretic deposition. The properties of polyamic acid–silica hybrid colloidal emulsion and polyimide–silica hybrid nanocomposite coating onto carbon fiber were characterized using laser diffraction, ZetaPlus Particle Sizing, transmission electron microscopy, field-emission scanning electron microscope, Fourier transform infrared spectroscopy and thermal gravimetric analysis. The results indicated that the small amount of nano-silica would be effectively dispersed in polyamic acid colloidal particles without aggregation and the nano-silica played an important role on keeping stability of polyamic acid–silica hybrid colloidal particles. The polyimide–silica hybrid nanocomposite coating carbon fiber displayed an excellent thermal stability up to 600 °C in the air (less than 5% weight loss for 8 h).