Change in Chemical Structure of ZnDTP-Derived Tribofilm Formed from Low-Viscosity Engine Oil by Addition of PMA-Series Polar Compounds

Abstract

The effects of Polymethacrylate (PMA)-series polar compounds on the friction and wear characteristics and on tribofilm formation in fully formulated low-viscosity engine oil have been studied. Optical microscopy, AFM, and element analyses by EPMA, AES, and XPS were used to determine the coexisting effects. The results showed that common additives in fully formulated (FF) oil had blocking effects that reduced the formation of ZnDTP-based tribofilm. PMA0 showed a blocking effect in preventing uniform tribofilm formation in FF low-viscosity oil. PMA-N showed comprehensive effects by forming a lower-quality uniform tribofilm in FF low-viscosity oil. PMA-OH and PMA-COOH showed a concerted effect by forming a lower S/P ratio and a higher Ca/Zn ratio uniform tribofilm in FF