How Hydrogen Bonding Affects Mechanical Properties of Simple Lithium Lubricating Grease

Abstract

Abstract. The effect of hydrogen bonding on the mechanical properties of lubricating greases (LGs) is examined. Four greases are prepared in an attempt to isolate the hydrogen bonding interactions within the LG system. Small amplitude oscillatory shear is first used to evaluate the viscoelastic moduli and crossover stress in the undisturbed state at varied temperatures. A 1-h full rotation shear is then applied to mechanically disrupt the LGs. The storage modulus is then tracked over time under varied temperatures to investigate modulus recovery. Our results show that hydrogen bonding within and between the thickener and oil plays a significant role in the mechanical properties in both the undisturbed and postdeformation states. Specifically, hydrogen bonding between the oil and the thickener increases the modulus and exhibits stronger temperature dependence. Hydrogen bonding within only the thickener increases the modulus with less temperature dependence. Overall, these results show that the interaction of functional groups between thickener–thickener and thickener–oil plays an important role in the mechanical properties and should be a design consideration.