Preparation and characterization of sustainable bio-cutting fluids: An analysis of tribological, rheological and thermal properties

Sustainable metal-cutting fluids derived from various edible and non-edible oil sources are gaining attention for their improved biodegradability and environmental friendliness. In this study, blends of waste cooking oil (WCO) and algae oil (AO) were prepared on a volume basis (90:10, 85:15, 80:20, 75:25, and 70:30), coded as 90WCO10AO, 85WCO15AO., etc. The blends of WCO and AO are examined for various significant properties, including thermal, rheological, tribological, and physicochemical properties, and compared with conventional neat oil. The experimental results, including functional group analysis, indicate that both oils have similar chemical structures and exhibit lubrication, film-forming, and coolant properties. The thermal characteristics (conductivity, diffusivity, and specific heat) are observed to have improved for WCO-AO blends compared to conventional neat oil, with typical improvements of 0.7–3%. The rheological properties of shear stress versus shear rate and viscosity versus shear rate, measured at 60 °C, reveal that WCO-AO blends (75WCO25AO and 80WCO20AO) exhibit improved shear rate and viscosity, ensuring better flow stability and load-bearing capability. The coefficient of friction indicates that the 75WCO25AO and 80WCO20AO blends exhibit similar conventional neat oil performance. Overall, blends of WCO with AO show improved results, and 80WCOAO resembles the optimal performance.