Role of Internal Additives in the Friction and Wear of Carbon-Fiber-Reinforced Polyimide

Polyimide composites should function in sliding contacts under high temperatures, but the interference of carbon fibers with sliding mechanisms is difficult to predict: they often increase the coefficients of friction and act abrasively but show lubricating properties under other conditions. The friction and wear behavior of thermoplastic polyimides reinforced with short carbon fibers and filled with solid internal lubricant (polytetrafluoroethylene) or silicon oil was investigated in this study with a reciprocating cylinder-on-plate tester under 50 N at 0.3 m/s with steel counterfaces that were heated at 23-260 degrees C. We concluded that polytetrafluoroethylene additives effectively reduced the coefficients of friction over the entire temperature range, especially tinder thermally controlled sliding conditions at 120 degrees C, whereas the internal silicon oil increased the coefficients of friction. The wear rates of the fiber-reinforced polyimide significantly decreased with respect to those of the thermoplastic polyimide, whereas additional fillers slightly increased the wear rates. We further analyzed the role of internal additives by considering the deformation and maximum polymer surface temperature during sliding. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116:1146-1156,2010