Hindered Phenol Derivative as a Multifunctional Additive in Lithium Complex Grease

This paper describes 3-(3,5-Di<i>tert</i>-butyl-4-hydroxy-phenyl)-propionic acid 2-(4-meth yl-thiazol-5-yl)-ethyl ester (BHMT) as a high-performance multifunctional additive in lithium complex grease (LCG). The tribological properties and antioxidant behaviors of BHMT were evaluated by the tribological test and thermal analysis, respectively, and compared with those of zinc dialkyldithiophosphate (ZDDP). The tribochemical film BHMT generated on the worn surface was analyzed by X-ray photoelectron spectroscopy (XPS). Tribological results indicated that BHMT exhibited better friction-reduction and antiwear properties than ZDDP. The thermal analysis demonstrated that the antioxidation ability of BHMT was superior to that of ZDDP. Moreover, XPS results showed that lubrication film composed of iron oxide, iron sulfate, and nitrogen oxide was formed on the worn surface, which was an explicit explanation of the tribochemical mechanism of BHMT