Methyl oleate derived multifunctional additive for polyol based lubricants

A novel multifunctional lubricant additive was synthesized by thiol-ene coupling of methyl oleate (Mo) with thioglycolic acid (Tga) to obtain intermediate compound Mo-Tga {(S)-2-(18-methoxy-18-oxooctadecan-9-ylthio)acetic acid} followed by esterification with 2,6-di-tert-butyl-4-(hydroxymethyl)phenol to obtain the final additive Mo-Tga-Bz {(S)-methyl 10-(2-(3,5-di-tert-butyl-4-hydroxybenzyloxy)-2-oxoethylthio)octadecanoate} in the second step. Since the sulfur and steric hindered phenol was introduced in methyl oleate framework, so the Mo-Tga-Bz was evaluated for anti-oxidant, anti-wear, anti-friction and anticorrosion characteristics in polyol lube base oil at the varying concentrations after confirming the molecular structure by FT-IR and NMR spectroscopic techniques. The anti-oxidant property was evaluated by DPPH (2, 2-diphenyl-1-picrylhydrazyl) method which showed a maximum free radicals %inhibition of 73.06 % at 0.5% (w/v) additive concentration; tribological properties were evaluated by four-ball test method which showed a reduction of 19.61% in average wear scar diameter (AWSD) at 0.2% (w/v) and 37.71% reduction in average friction coefficient at 0.3% (w/v) additive concentration comparative to polyol base oil. The anticorrosion activity test result revealed that Mo-Tga-Bz shows the concentration-effect but at 0.3% concentration the values for the weight loss, corrosion rate and penetration rate were decreased to a value of 1.39 +/- 0.07 mg, 1.44 +/- 0.07 mdd and 0.26 +/- 0.01 mpy respectively from 11.34 +/- 0.07 mg, 11.72 +/- 0.07 mdd and 2.16 +/- 0.01 mpy for polyol.