On the structure-activity relationship of glyceryl oleate friction modifiers and its synergistic mechanism on phosphate ester antiwear additives

Abstract

Abstract The structure-activity relationship of glyceryl oleate organic friction modifiers and the difference in interaction with antiwear additives significantly affect the friction and wear characteristics of the lubrication system. This paper comprehensively considers the differences between polar functional groups and hydrocarbon tail chains, a combination of experiments and simulations were used to investigate the structure-activity relationships of three glyceryl oleate friction modifiers and the synergistic antiwear mechanisms with phosphate ester additives. The results indicate that the reduction of hydroxyl groups in glyceryl oleate weakens the electrostatic interaction with the metal interface and hydrogen bonding interaction, and the increase in hydrocarbon tail chains leads to the enhancement of the steric hindrance effect. Resulting in the substitution of polar functional groups and the increase in hydrocarbon tail chains deteriorating tribological properties. In addition, the binary additive system of glyceryl monooleate and phosphate ester exhibits a significant synergistic antiwear effect. It is attributed to the chemisorption of additive O(C = O/P-O/P = O) active sites and the Fe2O3 metal interface, GMO hydrogen bond interactions, the deprotonation of phosphate ester, as well as the carbonate and phosphate protective film generated by tribochemical reaction.