Oxidative degradation of synthetic ester and its influence on tribological behavior

The oxidative degradation process and oxidation mechanism of di-2-ethylhexyl sebacate (DEHS) were studied in present work. GC–MS results revealed that 2-ethyl-1-hexanol and mono (2-ethylhexyl) sebacate were major degradation products in the liquid phase. Further investigation of degradation mechanism of DEHS showed that oxidation reactions and hydrolysis were main factors degradation of DEHS. The four-ball test results showed that chemical composition changes of DEHS during oxidation could significantly influence its tribological behavior. The formation of hydroperoxides in the initial oxidation period could seriously deteriorate lubrication properties of DEHS. However, as the oxidation proceeded, high polar products (acids, alcohols and monoesters) formed could significantly improve the anti-wear and friction-reducing properties of DEHS.

► The detailed degradation mechanism of di-2-ethylhexyl sebacate (DEHS) is proposed.
► Oxidation reactions and hydrolysis were main factors of degradation of DEHS.
► We first report the influence of oxidation on the tribological performance of DEHS.
► The tribological performance depends on the chemical composition change in oil.