Synergistic Friction-reducing and Antiwear Action of Oxygen and Sulfur Elements in Sulfurized Docosanoic Acid as Additive in Rapeseed Oil

Non-odour sulfurized docosanoic acid was prepared by low temperature vulcanization and metathetical reaction. Its load-carrying capacity, friction-reducing and antiwear properties as additive in rapeseed oil were evaluated using four-ball testers. The worn surface was analyzed with X-ray pho-toelectron spectroscopy (XPS), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). By comparison with docosanoic acid and sulfurized ios-butyl olefin, it was found that when sulfur element was introduced into docosanoic acid, oxygen andsulfurelementsshowedsynergistic friction-reducing, antiwear and load-carrying action. The analysisof the wornsurfaceshowsthat tribochemi-cal reactionsoccurred during friction process. Oxygen andsulfurelementswere enriched insurface protec-tive film of the worn surface.