Improving Tribological Performance of Porous Polyimide by Surface Polishing

Because of its self-lubricating qualities, porous polyimide(PPI)has been used as a crucial cage material for space bearings; however,overcoming the failure followed by blackening of PPI remains a challenge.Herein, we developed a surface smoothening approach to optimize thetribological performance of PPI in an oil-impregnated state. Pre-polishingusing sandpaper and then with Al2O3 paste enablesthe fabrication of nanoscale rough PPI surfaces with significantlyreduced friction and surface wear and complete suppression of theblackening phenomenon. Compared with polishing using sandpaper orAl(2)O(3) paste, the compound polishing method createda substantially smoother surface. It exposed more polytetrafluoroethyleneat the outermost surface, improving the liquid and solid lubricationproperties of the contact interface under a mixed lubrication state.The further analysis indicated that decreasing the size of PPI surfacepores during pre-polishing using sandpaper was crucial in resistingthe adsorption of residual polishing particles.