Triester derivatives of oleic acid: The effect of chemical structure on low temperature, thermo-oxidation and tribological properties

Due to the strict regulations imposed on mineral oil-based lubricants because of their non-biodegradable wastes, the development and applications of biolubricants are increasing daily. Plant oils are being investigated as a potential source of environmentally favorable lubricants because of their biodegradability, renewability, viscosity–temperature relationship, low volatility and excellent lubrication performance. However, the use of plant oils has some restriction, the most critical being oxidative stability and low-temperature problems. This paper presents systematic modifications to improve the physicochemical and tribological properties of plant oil derivatives. Thin-film micro-oxidation testing and pressure differential scanning calorimetry were used to compare the thermo-oxidative stabilities. The results showed that among the oleic acid-based triester compounds, 2-ethylhexyl 9-(myristoxy)-10-(heptanoyloxy)octadecanoate (9) had the lowest pour point (−47.19 °C) while 2-ethylhexyl 9-(caprooxy)-10-(heptanoyloxy)octadecanoate (5) had the highest onset temperature (103.10 °C) and the lowest amount of volatile loss and insoluble deposits at 89.17% and 78.51%, respectively. Overall, the data indicate that the biolubricant basestocks based on this chemical modification offer great potential for the development of industrial products.

► New branching triester of oleic acid based oils for biolubricant.
► Epoxidation, oxirane ring opening and esterification reactions have been employed.
► The biolubricant basestocks based on this chemical modification offer great potential for the development of industrial products.