Natural Antioxidant Extracted Waste Cooking Oil as Sustainable Biolubricant Formulation in Tribological and Rheological Applications

Developing eco-friendly formulations using waste cooking oil as renewable biomass is of great interest and commercial importance in the fuels and lubricant industry. This manuscript reports novel study on preparing a biolubricant formulations as WCO-1, WCO-2 and WCO-3 by blending the curcumin extracted soybean waste cooking oil in three different compositions viz 10%, 20%, 30% v/v with the mineral base oil N-150. Curcumin was extracted as a natural antioxidant in 0.5 wt% waste cooking oil to inhibit thermal oxidation. This study comprises a detailed analysis in terms of tribological, rheological and thermophysical characteristics such as viscosity, viscosity index, pour point and flash point parameters of the biolubricant by standard ASTM methods. Further, tribological and rheological analysis was done by the four-ball wear tester and Anton Paar, MCR-72, respectively. The thermophysical evaluation of WCO formulated biolubricant has shown excellent properties. The viscosity index of the formulated biolubricant increases with an increase in the concentration of waste cooking oil. In contrast, the pour point has also been depressing at lower temperature conditions. Thus, WCO based biolubricant was found to be more effective at extreme temperature conditions than the mineral base oil (N-150). Rheological studies have indicated the non-Newtonian behaviour of the biolubricant with an increase in shear rate. Whereas, tribological analysis demonstrates that wear scar diameter has significantly reduced from 0.685 to 0.573 mm, and the coefficient of friction decreased from 0.117 to 0.080 with respect to the mineral base oil. Thus, a straightforward green approach has been discovered by directly utilizing waste cooking oil for biolubricant formulation. GRAPHICAL ABSTRACT: [Image: see text]