Enhancing biodegradable lubricants with SiO2 and TiO2 nanoparticles: effects on viscosity, tribological behavior, rheological performance, and sustainability

The environmental impact of petroleum - based lubricants on marine ecosystems is significant, necessitating the development of sustainable alternatives. This study examines the effects of TiO2 and SiO2 nanoparticles on canola and wheat germ oil blends, aiming to enhance their industrial performance. Various formulations were evaluated for flash point, fire point, viscosity, tribological properties, rheology, stability, and biodegradability (BOD and COD values). The results demonstrated that TiO2 and SiO2 nanoparticles improve the thermal and tribological properties of vegetable oil-based lubricants. TiO2 nanoparticles notably enhanced flash point and viscosity, making the blends comparable to conventional automotive oils. Samples T-2 (TiO2) and S3 (SiO2) reduced the coefficient of friction (CoF) and wear scar diameter (WSD), indicating improved load distribution and reduced wear, making them viable for marine equipment and railway systems exposed to high friction. Rheological analysis revealed shear thinning and thickening behaviors at elevated temperatures, suggesting potential benefits for high-shear applications such as cutting tools, reducing tool wear, and improving surface finish. Zeta potential analysis showed that the S1 sample with SiO2 exhibited the best stability due to moderate negative charge, minimizing aggregation and ensuring consistent lubrication. Biodegradability assessments indicated that while TiO2 and SiO2 nanoparticles positively influenced environmental compatibility, the blends did not fully meet biodegradability standards (BOD/COD ratio < 0.5), suggesting the need for advanced treatment methods. This study highlights the potential of nanoparticle-enhanced vegetable oil lubricants for industrial applications, offering improved performance while contributing to sustainability. Further research is needed to evaluate their long-term effects and optimize biodegradability, reinforcing the shift toward eco-friendly lubrication solutions.