High performance lubricants prepared from Naphthalene-1,4,5,8-Tetracarboxylic acid: Synthesis, physicochemical and Tribological properties

Ester oils (1,4,5,8-4C_n) were synthesized through esterification of naphthalene-1,4,5,8-tetracarboxylic acid with aliphatic alcohols. The molecular structures were confirmed with ¹H NMR, ¹³C NMR, FT-IR and elemental analysis. Their KV, VI, FP, PP, oxidation and thermal stabilities, friction reducing and anti-wear performances were measured. The results demonstrate that the 1,4,5,8-4C_n have obviously higher thermal and oxidation stabilities than the existing esters DOS, PIS and Phe-3C_i8. They also have predominant tribological behavior at both 50 °C and 120 °C. Analyzing from the results of ECR, QCM and XPS, it could be concluded that strongly and orderly physicochemical adsorption of the 1,4,5,8-4C_n molecules on the sliding surfaces is the critical factor for these oils to demonstrate excellent tribological performance for steel contacts.