Tribological Study of a Novel Borate Ester Containing S, P with High Hydrolytic Stability as a Multifunctional Lubricating Additive

Abstract

Based on the “stable benzylic cation” theory, a novel borate ester with high hydrolytic stability was designed and synthesized. Its tribological properties as an additive in synthetic ester were evaluated using a four-ball tribometer. The results show that compared with ZDDP, the additive possesses outstanding loading-carrying and friction-reducing properties, and can improve the antiwear properties of the base oil dramatically. Moreover, its thermal stability, antioxidant performance, and hydrolytic stability were also evaluated, and indicated that the additive has excellent antioxidation performance, high hydrolytic stability, and high thermal stability. The worn surface of the steel ball was investigated by X-ray photoelectron spectroscopy (XPS) and the antiwear mechanism of the additive was preliminarily discussed.

KEY WORDS:

• Borate Ester Containing Dialkylthiophosphate Group
• ZDDP
• Extreme Pressure Additives
• Antiwear Additives
• Thermal Stability
• Oxidation Resistance
• XPS
• Hydrolytic Stability

ACKNOWLEDGEMENT

This work was sponsored by the National Basic Research Program of China (National 973 Program with Grant No. 2007CB607606). Meanwhile, the authors would like to thank Dr Xiaobo Wang at the State Key Laboratory of Solid Lubrication of Lanzhou, Institute of Chemical Physics of the Chinese Academy of Sciences, for their assistance in the tribological experiment and elemental analysis.

Review led by Elaine Yamaguchi