Lubricity, Tribological and Rheological Properties of Green Ester Oil Prepared from Bio-Based Azelaic Acid

Abstract

Plant oil derived compounds have been used as the raw material for the synthesis of green biolubricant. Azelaic acid derived from oleic acid is one of the interesting compounds. The synthesis of azelate esters oil based synthetic green biolubricants was carried out. The esterification process of azelaic acid with variety type of alcohols was catalyzed by concentrated H₂SO₄. The yields percentages of azelate esters oil produced were varied depending their overall molecular structure. The azelate esters oil properties were evaluated for their suitability as a biolubricant. The results showed that the linear azelate esters oil showed high pour point values in a range of 15 to 5 ºC for di-decyl azelate, di-octyl azelate and di-hexyl azelate respectively. On the other hands, the branch azelate esters oil showed very low pour point of -70, -58 and -50 ºC for di-2-butyloctyl azelate, di-2-ethylhexanol azelate and di-2-ethylbutyl azelate, respectively. Moreover, the linear azelate esters oil gave high values of flash point, viscosity index and oxidative stability, and they were slightly affected by branching molecule structure. The tribological and rheological properties of high molecular azelate esters oil were also performed. Subsequently, most of them were classified as non-Newtonian fluids and having boundary lubrication properties with low friction coefficient. The branch azelate esters oil is plausible to be used as green biolubricants in many applications including automotive, marine engine oils, compressor oils, hydraulic fluids, gear oils and industrial biolubricants.