Tribological Properties of Polyimide Coatings Filled with PTFE and Surface-Modified Nano-Si3N4

Polyimide (PI) coatings filled with PTFE and nano-Si3N4 were prepared by a spraying technique and successive curing. Nano-Si3N4 particles were modified by grafting 3-aminopropyltriethoxysilane to improve their dispersion in the as-prepared coatings. Friction and wear performances and wear mechanisms of the coatings were evaluated. The results show that the incorporations of PTFE and modified nano-Si3N4 particles greatly improve the friction reduction and wear resistance of PI coating. The friction and wear performance of the composite coating is significantly affected by the filler mass fraction and sliding conditions. PI coating incorporated with 20 wt % PTFE and 5 wt % modified nano-Si3N4 displays the best tribological properties. Its wear rate is more than one order of magnitude lower and its friction coefficient is over two times smaller than that of the unfilled PI coating. Differences in the friction and wear behaviors of the hybrid coatings as a function of filler or sliding condition are attributed to the filler dispersion, the characteristic of transfer film formed on the counterpart ball and the wear mechanism of the coating under different sliding conditions. (c) 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40410.