Wear and friction performance of PTFE filled epoxy composites with a high concentration of SiO2 particles

In this work, the tribological performance of PTFE filled SiO2 particles-epoxy composites is investigated. Under a load of 60 N (~140 MPa contact pressure), the optimum content of PTFE lies between 10 and 15 wt%, which yields an ultralow coefficient of friction (CoF) in conjunction with a low wear rate of the composite when dry sliding against bearing steel balls within 1000 m. With 12.5 wt% PTFE in the composite, a CoF around 0.095 and a wear rate as low as 8.4×10−7 mm3/Nm were measured up to a sliding distance of around 2000 m. After 2000 m, eventually the gradual accumulation of the fractured SiO2 particles and back-transferred steel on the worn composite surface leads to a significant increase of CoF. In the steady-state of sliding, smearing of the PTFE particles along the worn surface was observed together with fracturing of the SiO2 particles and cracking of the epoxy matrix. Successive EDS mapping shows the formation and evolution of a PTFE-containing third-body tribolayer on the worn surface of the composite. The thickness of the tribolayer was measured about 20-30 nm on the surface of SiO2 particles after sliding for more than 700 m.