Tribological performance and action mechanism of S-alkyl and S-benzimidazole substituted dialkyldithiocarbamates

Two new derivatives of dioctyldithiocarbamate, one containing heterocyclic group (benzimidazole) and another being an aliphatic compound, were synthesized and characterized. Their tribological performances as lubricant additives in liquid paraffin were evaluated by four-ball and SRV friction and wear testers. The results showed that S-benzimidazole substituted dioctyldithiocarbamate (BMZ–C8) possesses excellent tribological properties, its friction reducing ability and anti-wear property at high loads are comparable to that of zinc dialkyldithiophosphate (ZDDP). However, the tribological performance of S-ethyl substituted dioctyldithiocarbame (HY–C8) is worse than BMZ–C8. The rubbed surfaces were investigated using X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES) and Scanning Electron Microscopy (SEM). The action mechanisms of additives were also proposed.