Study on the Friction and Wear Properties of Polyimide Composites Filled with Polytetrafluoroethylene and MoS2

The friction and wear properties of the polyimide (PI) composites filled with polytetra-fluoroethylene (PTFE) and molybdenum disulfide (MoS_2) particulates sliding against GCr15 steel under dry friction condition were studied using an MM-200 ring-on-block friction and wear tester. The worn surfaces of the PI composite blocks and the counterpart steel rings were observed using a scanning electron microscope and energy dispersive spectroscope. It was found that PTFE and MoS_2 as the fillers contributed to improve the friction and wear behavior of PI. Namely, all the filled PI composites except for PI+10%PTFE+20%MoS_2 showed much better wear-resistance than the unfilled PI, for example, the PI+20%PTFE+10%MoS_2 composite registered a wear rate smaller than that of the unfilled PI by 1 order of magnitude, and the filled PI composites had smaller friction coefficients than the unfilled PI as well. Moreover, the PI+30%MoS_2 composite showed the best friction-reducing and antiwear behavior among all the composites tested, which indicated that the inorganic and organic complex fillers did not necessarily have synergistic effect in terms of their ability to improve the friction and wear behavior of PI. The improved friction and wear behaviors of the filled PI composites were closely related to the characteristics of their transfer films formed on the counterpart steel surface. The composites capable of forming the transfer film with proper thickness and even distribution had better friction and wear behaviors.