Thermo-tribological behaviour of microgels for improved aqueous lubrication for steel/UHMWPE contact

The thermo-tribological behaviour of 316L stainless steel/ultrahigh molecular weight polyethylene (UHMWPE) contacts under aqueous lubrication was investigated in this work. Thermo-responsive microgels were prepared and used as lubricant additives in aqueous solutions. Tests were conducted using a reciprocating tribometer, over a range of temperatures and microgel concentrations. The microgels were shown to have temperature-dependent friction-reducing and anti-wear properties. The microgels acted as load bearing particles in the water, rolling and sliding between frictional interfaces. A maximum recorded friction coefficient coincided with a phase-transition in the microgels induced at a lubricant temperature of 32 °C. This was indicative of a thermo-tribological sensitivity in the microspheres, whereby particle size and shape changed with temperature, affecting tribological performance. These changes included structural collapse of the microgels due to dehydration at the critical temperature. This characteristic temperature-sensitivity in the microgels offers new strategies for controlling friction and wear of steel/UHMWPE contacts under aqueous lubrication.