Influence of hindered phenol on the tribochemistry of polysulfides in mineral oil and synthetic diester

The influence of hindered phenol on tribological properties and mechanism of polysulfides in mineral oil and synthetic diester were investigated in this paper. Four-ball machine was employed to evaluate the anti-wear and friction-reducing performance of the lubrication system and X-ray absorption near-edge structure spectroscopy was applied to detect the thermal and tribofilms. The tribological results indicate that when the phenol was added in trisulfide/synthetic diester system, the friction coefficient decreased. The anti-wear performance of sulfides only depended on the concentration of sulfur in mineral oil. The results of X-ray absorption near-edge structure analysis indicate that sulfite can be found in thermal films by adding hindered phenol into mineral oil with trisulfide, while in other conditions, the thermal films only consist of sulfate. The results of the tribofilms show that for the trisulfide in mineral oil, hindered phenol changes the ratio of reduced and oxidised form of sulfur. Copyright © 2016 John Wiley & Sons, Ltd.