Oil Viscosity Effects on Lithium 12-Hydroxystearate Grease Modulus and Thixotropy

Abstract

The effect of base oil viscosity and temperature on the thixotropic recovery of lubricating grease (LG) is investigated via shear rheology. The viscosity of the base lubricant phase of LGs impacts the storage modulus in both the undisturbed and post-sheared states. In this study, we focus on three greases with varied base oil viscosity but similar chemistry: polyalphaolefin (PAO) 8, PAO 40, and PAO 100. Small amplitude oscillatory shear testing is first used to evaluate the viscoelastic modulus in the undisturbed state at varied temperatures. A one-hour full rotation shear is then applied to mechanically disrupt the LGs. The storage modulus is then tracked over time under varied temperatures to investigate thixotropic recovery. These results show that the physical properties of the fluid phase of LGs can significantly impact the mechanical properties of the solid phase present in LGs and that the storage moduli is a function of the state related to temperature.