N-Oleoyl Sarcosine as an Engine Oil Friction Modifier, Part 2: Elucidation of Friction-Reducing Mechanism at Room Temperature Focusing on Contribution of NOS in NOS+ZDDP Mixture

Abstract

The tribological properties of a mixture of a commercial organic friction modifier, N-oleoyl sarcosine (NOS), and a commercial anti-wear additive, zinc dialkyldithiophosphate (ZDDP), were investigated. The results suggest a synergistic effect between these two additives, resulting in a mixture that exhibited the lowest and most stable friction coefficient as well as the smallest wear area. X-ray photoelectron spectroscopy was performed to investigate the chemical composition of the tribo-films formed using this mixture. The results suggest that the tribo-films lacked S as well as PO43− species. They also suggest that ZDDP mitigates degradation of the NOS, and improve the tribo-film durability thus improving anti-wear/friction-reducing performance. These results elucidate the synergistic friction-reducing tribological mechanism of the NOS+ZDDP mixture.

Keywords

• zddp
• organic friction modifiers
• boundary lubrication
• xps
• ball on disc