Linseed and Complex Rosin Ester Oils Additivated with MWCNTs and Nanopearls for Gears/Wheel-Rail Systems

An innovative biolubricant for gears/wheel-rail systems is formulated; it is produced inexpensively using high-viscosity vegetable oils modified with additives of unpurified carbon nanopearls (CNPs) and MWCNTs produced via carbon-vapor deposition. Traditional lubricants made from non-renewable sources can be replaced with such additive-based oils. The addition of both unpurified carbon nanopearls and nanotubes containing nanoparticles of Fe, Ni, Co, or SiO₂ is a simple way to improve the tribological properties of biolubricants. Therefore, carbon nanostructures used as additives are not required to be purified or functionalized, thus reducing production costs. Tribological testing is performed with ball-on-disc, four-ball, and twin-disc machines for two high-viscosity biolubricants. A complex rosin ester and linseed oil additivated with commercial and raw CNPs/MWCNTs are tested. Scanning electron microscope characterization is used to assess the morphology and structure of both the carbon nanopearls and the multiwalled carbon nanotube particles in addition to the worn metal surfaces. Additionally, X-ray diffraction, FTIR spectroscopy, and inductively coupled plasma atomic emission spectroscopy are used to characterize the MWCNTs additives. Practical Applications: Biolubricant additivation with raw unpurified MWCNTs and CNPs for enhanced tribological performance. Presence of Fe, Ni, Co, and Si nanoparticles helps fine-tune the friction coefficient and anti-wear rates. The proposed method may prove useful in biolubricant formulation for applications in gears/wheel-rail and metal machining systems.