Non-edible/waste cooking oil-derived sustainable green multifunctional copolymeric additives for mineral base oil

The greener additives have drawn considerable awareness in the lubricant industry due to their biocompatibility and multifunctional behaviour compared to conventional additives. In this study, novel multifunctional copolymer additives (MCAs) were synthesised from non-edible/waste cooking oil with stearyl methacrylate via addition polymerisation in the presence of benzoyl peroxide as a free radical initiator. The copolymeric additives derived from castor oil and waste cooking oil are named as MCA-1 and MCA-2, respectively. The prepared additives have been characterised by routine NMR and FT-IR spectroscopy, whereas the molecular weight and thermal-oxidative stability of the copolymers were determined by gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) respectively. Doping of the synthesised multifunctional green additives in terms of viscosity index improver (VII), pour point depressants (PPD) in base oil (N-150) have been determined using standard ASTM methods. The rheological behaviour of the doped base oil was examined using Anton Par MCR-72 in different concentrations of additive, viz. 1%, 1.5%, and 2% (w/v). The performance of the doped oil was compared with base oil. The additives were found to show the multifunctional behaviour in terms of pour point depressant, viscosity index improver, and rheology modifier. The improvement in viscosity with respect to base oil is in close agreement with the rheological study, which shows shear-thickening property with an increase in the concentration of additive. The significance of the study lies, in fact, the viscosity of the lubricant increases with shear rate and then decreases, making it suitable under the varying condition of temperature. Moreover, waste cooking oil can be used as a promising alternative for the preparation of environmentally friendly multifunctional additives. It is cheaper, readily available, renewable, and non-edible oil over conventional, expensive edible oil for the formulation of lubricants.