Tribological performances of hybrid composites of Epoxy, UHMWPE and MoS2 with in situ liquid lubrication against steel and itself

In this paper, hybrid polymeric composites of epoxy with two solids (UHMWPE and MoS2) and one liquid (base oil SN150) fillers were prepared to improve the thermal, mechanical and tribological properties for load bearing applications. Due to relatively high friction of solid lubricants compared to liquid lubricants, base oil was incorporated into the epoxy composite as liquid filler to achieve enhanced tribological properties. All the experiments were conducted with two interfacial conditions: polymer composite against steel (EN31) and polymer composite against itself. The base oil-filled epoxy composite showed excellent tribological performance with specific wear rate in the range of 10-7 mm3/Nm and low coefficient of friction of 0.08-0.1 at a constant nominal contact pressure of 0.611 MPa and speed 1 m/s. Durable transfer film formation was identified as the main wear reduction mechanism. These fillers also made the surface of epoxy hydrophobic in nature which reduced adhesion and friction. By adding fillers, thermal degradation temperature of the composite was increased by 22.8%. The lubrication mechanism was identified as mixed lubrication with three different sub-regimes.