Particle size effect of PTFE on friction and wear properties of glass fiber reinforced epoxy resin composites

Self-lubricating spherical plain joint bearings play a crucial role in aerospace equipment, with their performance primarily depending on the self-lubricating materials positioned between the inner and outer rings. As a typical polymer-based self-lubricating material, glass fiber reinforced epoxy resin composites receive high expectations. Polytetrafluoroethylene (PTFE) as an additive can significantly improve the friction and wear performance of glass fiber reinforced epoxy resin composites. The primary objective of the present study is to reveal the effect law of PTFE particle size on friction and wear properties of glass fiber reinforced epoxy resin composites under dry sliding conditions. Hence, the four particle sizes (P1, average < 1 μm; P2, average 12 μm; P3, average 25 μm; P4, 75–180 μm) of PTFE-filled epoxy composites were prepared. The hardness, compressive strength, and compressive modulus of the epoxy resin composites filled with four particle sizes of PTFE were measured. The coefficient of friction (COF) was evaluated using a reciprocating ball-on-disk tribometer, with a GCr15 ball as the stationary part and the composite disc as the reciprocating component. The wear rate was determined using a Mahr profilometer. The results show that the friction coefficients of four PTFE-filled epoxy resin composites have little difference. However, the wear rate of epoxy composite filled with PTFE particles of the large size (RE/P4) is an order of magnitude lower than that of epoxy composites filled with PTFE particles of the other size. The wear morphology of the composites was analyzed by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The higher wear resistance of RE/P4 can be attributed to it exhibiting a stronger role in anchoring glass fibers (GF), compared to other particle-sized PTFE-filled epoxy resin composite materials.