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This study aims to develop synthetic ester lubricating oil using renewable sinapic acid as raw material, to explore the structural design and selection of raw materials for green, high-performance synthetic ester oils.

A series of the sinapate ester oils were synthesized through esterification and alkoxylation reactions using renewable source sinapic acid as the raw material. The molecular structures of the oils were characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy spectroscopy and elemental analysis. The oils were evaluated for safety, viscosity-temperature properties, thermal and oxidative stability, as well as friction reducing and anti-wear characteristics.

Compared to commercial base oil tris (2-ethylhexyl) trimellitate (Phe-3Ci8), the bio-lubricant exhibits superior antifriction and anti-wear properties. Notably, the JCi8-C12 sample performed exceptionally well, reducing the friction coefficient by 11.42% and wear volume (WV) by 54.44% in steel/steel tribo-pairs. In steel/aluminum tribo-pairs, the friction coefficient decreased by 27.48%, while WV was reduced by 85.81%. Mechanistic studies reveal that the introduction of short-chain methoxy groups and stable conjugated systems (aromatic rings and double bonds) inhibit oxidation and decomposition at elevated temperatures. The p-p stacking effect enables lubricant molecules to arrange stably on friction surfaces, forming a durable lubricating film.

The utilization of biomass resources to develop green synthetic lubricating oil with excellent performance not only enhances the added value of waste from agricultural processing but also offers significant benefits in terms of both economic and environmental sustainability.

Nano graphitic-carbon nitride (g-C₃N₄) is an emerging lubrication technology with excellent performance and significant potential for future applications. This study aims to investigate the effect of nano g-C₃N₄ as a lubricant additive on the wear performance of bearing steel disk.

Various mass fractions of g-C₃N₄ were introduced into the base oil. Combining tribological testing, rheological testing and surface analysis methods, the anti-wear properties and lubrication mechanisms were analyzed.

Transmission electron microscopy images revealed that the size of the nanoparticles of g-C₃N₄ ranges from 10 to 100 nm. Phase analysis of the g-C₃N₄ sample was conducted using X-ray diffraction. Further, 1.0% mass fraction of g-C₃N₄ in the base oil provides excellent anti-wear and friction-reducing performance. Compared to the base oil alone, it reduces the average friction coefficient by 63.8% and decreases the wear rate by 43.1%, significantly reducing the depth and width of the wear scar. Energy-dispersive X-ray spectroscopy and scanning electron microscope analysis revealed that the oil sample containing nano g-C₃N₄ can form a lubricating film on the sliding surface of bearing steel after wear, which enhances the lubricating properties of the base oil.

The synergistic effect of the base oil and nanoparticles reduces friction and wear and is expected to extend the service life of bearing steel. These findings suggest that incorporating nano g-C₃N₄ as a lubricant additive offers significant potential for improving the performance of mechanical components.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2024-0456/