Effect of PTFE and Some Additives of Engine Oil on Tribological Properties between Polyamide and Carbon Steel

Abstract

Effect of polytetrafluoroethylene (PTFE) and some additives of engine oil on tribological properties between polyamide (PA) and carbon steel was studied with a pin-on-disk type tribometer. Friction and wear properties of PA were improved by blending PTFE of 10 mass% into PA matrix, in which chemically blended material f-PTFE/PA was superior to physically blended material PTFE/PA. This is because f-PTFE/PA has a characteristic surface with fine PTFE particles dispersed in PA matrix, while the surface of PTFE/PA has agglomerated PTFE particles easily removed when rubbing. Then, the effect of lubricating oils on tribological properties of PA was studied using the additive free hydrocarbon oil and the fuel-saving type engine oil. The friction-sliding speed characteristics were evaluated taking practical use in automobiles into consideration. The coefficient of friction under the low sliding speed region was much lower for the engine oil than for the hydrocarbon oil. In addition, the engine oil showed a flat friction-sliding speed curve while the hydrocarbon oil showed a curve with large negative gradient. By surface analysis on the rubbed surface and by conducting additional experiments, it became clear that Ca-detergent containing CaCO₃ in the engine oil was effective for improvement of the friction and wear properties between PA and carbon steel.