In this study, we have investigated the lubricating properties of an aqueous fluid prepared with polyoxamer triblock copolymer in water, namely 'F127-20' (F127 at the concentration of 20% wt./vol.). In coherence with its well-known thermo-responsive rheological properties, lubricating properties of F127-20 also displayed varying lubricating properties, both in the lubricating mechanism and efficacy, as a function of temperature, speed and tribopairs. F127-20 was most effective in lubricating a soft interface (PDMS-PDMS) based on its gel-forming properties in 22.5-60 °C and feasible formation of hydrodynamic lubricating films at all speeds. More importantly, enhanced shear thinning of F127-20 and an optimum pressure opposed from PDMS-PDMS tribological contact led to a substantial reduction in viscosity of the lubricant and smooth gliding of the interface while maintaining fluidic lubricating films. At temperatures lower or higher than temperature range 22.5-60 °C, F127-20 behaved as a liquid, and boundary lubrication became the dominant lubrication mechanism.
Ron, Troels, Ioannis S. Chronakis, Seunghwan Lee