Evaluation of multifunctional green copolymer additives–doped waste cooking oil–extracted natural antioxidant in biolubricant formulation

In recent years, transportation and industrial sectors have been utilising petroleum-based products to a great extent. But, these products are creating havoc on the environment by causing pollution and raising concern about future energy security. Therefore, waste cooking oil is the best choice as waste biomass, a healthy substitute over mineral oil for the lubricant sector. In this study, curcumin-extracted waste cooking oil (WCO) derived from soybean oil has been doped with multifunctional green additives MGA-1 and MGA-2, namely copolymeric additives derived from the polymerisation of stearyl methacrylates and sunflower/soybean oil, respectively. Furthermore, additives-doped, curcumin-extracted WCO has been formulated with mineral oil (N-150), and the results have been compared. In the present study, these additives MGA-1 and MGA-2 are blended in different concentrations viz 0.50%, 0.75%, and 1.0% (w/v) with curcumin-extracted WCO, and it was formulated with mineral base oil N-150 in different ratios (10%, 20%, 30% v/v). The thermal stability and antioxidant behaviour of the curcumin-extracted waste cooking oil were examined by thermogravimetric analysis (TGA) and FT-IR, respectively. Thereafter, formulated biolubricant was analysed for physicochemical characterisation, including kinematic viscosity, dynamic viscosity, viscosity index, pour point, flash point by standard ASTM methods, and rheological analysis to study their flow behaviour using Anton Paar MCR-72. The MGAs-doped-formulated biolubricant shows an increase in viscosity index with an increase in the concentration of the additives, whereas the pour point of the biolubricant depresses at lower temperature conditions. The rheological study has shown the non-Newtonian shear thickening behaviour of the biolubricant. Thus, both the additives show multifunctional behaviour in terms of viscosity, viscosity index, pour point and rheology modifiers. The significance of the study lies in the fact that viscosity has been increased with shear rate, which makes the MGAs-doped biolubricant feasible at extreme temperature conditions. Thus, a novel approach has been discovered by utilising waste cooking oil as the base oil for multifunctional green additives. Graphical abstract