Tribological studies on a novel borate ester containing benzothiazol-2-yl and disulfide groups as multifunctional additive

A novel borate ester derivative containing benzothiazol-2-yl and disulfide group (BTSB) was synthesized and characterized. Its tribological properties used as EP and multifunctional additive in rapeseed oil were evaluated using a four-ball tribometer, and its action mechanisms were investigated by the X-ray photoelectron spectroscopy. Results show that the BTSB possesses comprehensive tribological properties in load-carrying, friction-reducing, antiwear, corrosion-inhibiting, and anti-oxidation, which probably has a chance to replace ZDDP partially. Moreover, the decomposed borate esters, organic sulfide and nitrogen adsorbed on worn surface were detected, and S element in BTSB reacted with metal and generated FeSO4, both of which contributed to the formation of boundary lubricating film.