Abstract: Environmentally friendly boron-containing soybean lecithin (BSL) was synthesised. Constant temperature and humidity box was applied to evaluate the hydrolytic stability of the novel lubricant additive. The friction-reducing, anti-wear, and extreme pressure performance of BSL in synthetic base fluids were studied by an optimol SRV-I oscillating reciprocating friction and wear tester and four-ball tester. The hydrolytic resistance test results reveal that BSL possesses good hydrolytic stability. Tribological tests show that the friction-reducing performance of BSL in A51 is inferior to PAO10. The incorporation of BSL in synthetic basestock can dramatically reduce the wear volume of the lower steel disc under different test conditions. BSL can also enhance the load-carrying capacities of the synthetic base fluids. Morphology and chemical composition of the wear surface were characterized by scanning electron microscope and X-ray photoelectron spectroscopy. The results indicated that excellent tribological performance of the BSL can be attribute to the formation of chemisorption and chemical reaction protecting films composed of Fe₂O₃, iron polyphosphates, organic amines, and BN, etc.

Predicted molecular structure of BSL derived from PC

Conclusions

Environmental friendly BSL was synthesised and studied as a multifunctional lubricant additive in synthetic base fluids. Due to the electron-donating and steric hindrance effect, BSL possesses good hydrolytic stability. The incorporation of 1 % BSL in both PAO10 and A51 could reduce the friction coefficient and wear volume. The PAO10 was more compatible with BSL. The anti-wear performance of BSL in synthetic base fluids was slightly affected by applied load and temperature, suggesting that BSL could control wear under different working conditions. Four-ball extreme pressure test showed that the BSL can enhance the load-carrying capacity of the base fluids. SEM and XPS results revealed that the good tribological performance could be attributed to the formation of chemisorption and tribo-chemical reactions films composed of Fe₂O₃, iron polyphosphates, organic amines, and BN, etc.