The tribological behavior of nanometer and micrometer TiO₂ particle-filled polytetrafluoroethylene/polyimide

The friction and wear properties of micrometer and nanometer TiO₂ particle-filled polytetrafluoroethylene (PTFE)/polyimide (PI) composites were studied in this paper. The effect of filler contents (0.5%, 1%, 1.5%, 2%, 3%, 5% and 7vol.%) on the tribological properties was examined. The transfer films and the worn surfaces of the PTFE/PI composites filled with micrometer and nanometer TiO₂ particles were investigated by using a scanning electron microscope (SEM). Experimental results show that anti-wear properties of the PTFE/PI composites can be improved greatly by filling nanometer TiO₂ particles. The wear rate of 1.5% nanometer TiO₂ filled composite is the lowest, which is about 52% lower than that of PTFE/PI. In the case of micrometer TiO₂ filler, the friction coefficient and wear rates increase with increasing filler volume fractions under identical test conditions. It was also found that the wear mechanism of micrometer TiO₂ particle-filled PTFE/PI is mainly severe adhesion and abrasive wear, while that of nanometer TiO₂ particle-filled PTFE/PI is mainly slight abrasive wear.