KEYWORDS

Lubricants, Viscosity Modifiers, High Pressure, Elastohydrodynamic Lubrication, Viscosity

PRESSURE-TEMPERATURE VISCOSITY MEASUREMENTS AND SIMULATIONS OF LUBRICANTS WITH VISCOSITY MODIFIERS

Previously, we reported the observation of anomalous pressure and temperature dependent increases in viscosity of some commercial engine oils and specific polymers blended with mineral and synthetic oils. The onset of sharp increases in viscosity was attributed to pressure-driven phase transitions occurring in some of the polymer viscosity modifiers (VM). In this study, several other commercial engine and gear oils (mineral-, synthetic-, and bio-based) and laboratory produced lubricants have been tested up to 1.4 GPa and temperatures of 40, 75 and 100 °C. The pressure-driven phase transitions occurring in polymers commonly used as lubricant viscosity modifiers are correlated with the physical properties of the polymers, and impact of the rheological properties of the lubricants on the EHD film thickness is studied. A modified William-Landel-Ferry-Yasutomi relationship has been used to model the rheological behavior of commercial engine oils and laboratory synthesized lubricant blends.

AUTHORS

B. LotfizadehDehkordi, The University of Akron, Akron, OH, P.J. Shiller and G.L. Doll, Timken Engineered Surfaces Laboratories (TESL), The University of Akron, Akron, OH, K.K. Mistry, The Timken Co., North Canton, OH, U. Ramasamy and A. Martini, University of California-Merced, Merced, CA