Tribological behaviours of carbon filled polytetrafluoroethylene (PTFE) dry journal bearings

Most fundamental laboratory studies on the tribological behaviours of polymers have been performed on the rigs which are in line with pin-on disc or pin-on ring models. The calculation of polymer bearings have been generally based on the data obtained from these studies. But bearings have special geometrical and kinematical characteristics. That is why the calculation can only give a general idea. In this study, the effects of sliding distance, bearing pressure, the medium and low speed on friction and wear in journal bearings made of 35% carbon filled PTFE composite are experimentally examined. The results of experiments are presented in tables and graphics which proves that the coefficient of friction and the wear are strongly influenced by the thickness and composition of these films depending on the adhesion between steel and composite surfaces, the cohesive properties of the polymer used, pressure and the sliding distance. Taking into consideration the large number of factors, and their widely fluctuating characters and effects on the friction and wear; an optimum bearing construction may only be achieved through experiments.