Lubricating performances of oil-miscible trialkylanmmonium carboxylate ionic liquids as additives in PAO at room and low temperatures

Ionic liquids (ILs) have recently been demonstrated as a promising lubricating material. However, data on ILs with splendid solubility in non-polar oil and their low-temperature lubricating performances are rarely reported. In this paper, we synthesized four novel oil-miscible protic ionic liquids (PILs) containing different fatty acid anions. They possess low pour point, good low-temperature fluidity, non-corrosiveness and higher thermostability. These PILs were selected as additives in PAO base oil, respectively, and their lubricating performances were tested using a steel ball reciprocating sliding against steel stationary disc at room and low temperatures. At room temperature (similar to 30 degrees C), [N888H]C6 with shorter alkyl chains exhibited good lubricating behaviors, both in terms of steady-state friction coefficient and wear volume. However, the lubricating performances of [N888H]OA with longer alkyl chains were relatively poor because the lubricating film formed by it is disordered. At low temperature (-20 degrees C), these PIL additives produced excellent antiwear performances, while their friction-reducing properties were unobvious, attributing to the restriction of high kinematic viscosity of PAO base oil.

Automated summary

This study synthesized four novel oil-miscible protic ionic liquids with excellent low-temperature lubricating performance and thermal stability. Under room temperature conditions, the ionic liquid with shorter alkyl chains exhibited good lubricating behavior, while the one with longer alkyl chains showed relatively poor lubrication performance. At low temperatures, these ionic liquid additives demonstrated outstanding antiwear properties but had less noticeable friction-reducing effects due to the high kinematic viscosity of the PAO base oil.