Evaluation of antioxidants in rapeseed oils for railway application

In order to evaluate the applicability of biodegradable base-oil lubricants for railway applications, the influence of UV(ultraviolet)-B light (280–320 nm) on oxidation stability and the tribological performance of rapeseed oil (RO) have been investigated. Antioxidant free RO was oxidized immediately under UV-B irradiation at moderate temperature. Three sterically hindered phenolic-type antioxidants, pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 2-6-di-tert-butyl-4-methyl phenol were tested in order to increase the oxidation stability of RO. Pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) was the most effective, prolonging the oxidation induction time from 3 h of RO to 40 h. The tribological performance of RO could be improved by the addition of metallic detergent (Ca–alkylsalicylate–CaCO3) and was stable against the UV-B irradiation.