On the rheological behaviour of synthetic fluids thickened by solid additives

A variety of fluid space lubricants, i.e., synthetic oils thickened by solid additives (particles of PTFE and MoS₂), has been developed. These lubricants present a solid-like behaviour under yield stress, and a strong non-Newtonian effect during flow. Measurement of the yield stresses revealed an unexpectedly strong interaction between a synthetic hydrocarbon oil and one type of PTFE particle. Furthermore, the substitution of 1 vol.% PTFE particles by MoS₂ particles introduced a significant change in the yield stress values. This effect is also apparent in viscosity measurements. These lubricants display, through their rheological behaviour, good ability to replenish contacts over a wide range of temperatures, as shown by measurements taken at −20°C and −60°C.