Vegetable oil-based ethanolamides as potential anti-oxidant additives for lubricant formulations

Novel antioxidant mono- and diethanolamide, eight additives were prepared from castor oil, coconut oil, thumba oil and sal fat. These were evaluated for antioxidant efficacy taking epoxy karanja oil as base oil at 0.5-5% concentration. Antioxidant tests were performed on Rotating Pressure Vessel Oxidation Test RPVOT and Differential Scanning Calorimetry DSC. Among the prepared mono and diethanolamides, only diethanolamide-based additives exhibited potential anti-oxidant behavior. Coconut diethanolamides containing saturated medium chain fatty acids exhibited excellent stabilities, followed by diethanolamides of sal rich in saturated long chain fatty acids. The castor based diethanolamides rich in mono unsaturated hydroxy fatty acid showed slightly lower stabilities, while thumba with polyunsaturation exhibited poor oxidation stabilities.  Both the methods have shown that the fatty diethanolamides exhibited extraordinary stabilities compared to commercial antioxidant, butylated hydroxy toluene BHT at 1-5% concentration. The study indicated that the presence of saturation and medium chain fatty acids in the diethanolamide-based additives improved the oxidation stability of the base oils.