An investigation on the friction of oriented polytetrafluoroethylene (PTFE)

Measurements of the friction coefficient of oriented polytetrafluoroethylene (PTFE) have been made and the results indicate that the friction coefficient of drawn PTFE is dependent on the oriented direction. The worn surfaces were observed using an atomic force microscopy (AFM). The crystallinity of the transfer film was determined using differential scanning calorimeter (DSC). Friction orientation was found to be an important character of PTFE tribology. The friction-induced orientation occurred on the worn surfaces and the transfer films with high crystallinity were formed on the counterparts, which was one of the causes for the relatively steady friction coefficient in the sliding process. However, the formation of the friction-induced orientation on the worn surfaces and the transfer film did not change the anisotropy of the friction coefficient for drawn PTFE under our experimental conditions. Although this result meant that the bulk-oriented structures of PTFE play an important role on its friction processes, the formation of better friction-induced orientation could result in the lower friction coefficient.