Synthesis of a novel borate ester containing a phenylboronic group and its tribological properties as an additive in PAO 6 base oil

To reduce the dosage of zinc dialkyldithiophosphates (ZDDP) in engine oil, the synthesis and characterization of a novel borate ester containing a phenylboronic group (BDDP) was reported. The thermogravimetric analysis results showed that BDDP had a better thermo-stability compared with that of commercial additives ZDDP and F10A. The tribological properties of the PAO 6 base oils containing BDDP, ZDDP and F10A were studied using a four-ball tester and SRV tribo-meter. The oil with a BDDP concentration of 0.8% showed tribological properties superior to those of the ZDDP and F10-containing oil under varying applied loads and elevated temperature conditions. The elemental composition of the tribological film generated on the worn surfaces of the steel balls was detected by X-ray photoelectron spectroscopy (XPS), and the results indicated that the tribological film was composed of Fe2B and B2O3. Thus, BDDP could be a candidate to replace ZDDP or reduce the dosage of ZDDP in engine oil.