Description:
PurposeAs multifunctional additives, ZDDP, which provides excellent oxidation resistance and superior antiwear properties, has been used widely in lubricants, however, it shows oppositional effect with friction modifiers when used together. In this paper, an attempt is made to find a novel kind of borate ester which can be used as potential substitute for ZDDP.Design/methodology/approachA novel borate ester containing dialkylthiophosphate group was prepared and characterized. Its tribological properties as an additive in synthetic ester were evaluated using a four‐ball tribometer and antioxidative ability tested by pressurized differential scanning calorimetry (PDSC). Thermal degradation tests were conducted to identify its thermal stabilities using thermogravimetric analyzer (TGA). 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.FindingsResults show the additive possesses outstanding loading‐carrying and friction‐reducing properties, compared with ZDDP, and can improve antiwear properties of the base oil dramatically. Moreover, it also has excellent antioxidation performance and thermal stability.Originality/valueThis paper provides a multifunctional ashless additive which possesses excellent tribological properties, and gives another selection for industrial applications in which ZDDP is needed.