Dewi Ambarwati, Poppy Puspitasari, Diki Dwi Pramono, Muhammad Kozin, Tadiwa Elisha Nyamasvisva, Ibrahim Dauda Muhammad
Waste cooking oil (WCO) was valorized into an eco-friendly biolubricant and further enhanced with titanium dioxide (TiO2) nanopowder (0.15 wt%) for aluminum alloy 6061 (AA6061) sliding contacts. WCO was converted to fatty acid methyl ester (FAME) and subsequently transesterified with ethylene glycol to produce the base biolubricant, while TiO2 was dispersed by stirring–sonication. Physicochemical (density and Fourier transform infrared spectroscopy, FTIR), rheological (viscosity– temperature and Vogel–Tammann–Fulcher, VTF, modeling), thermal (thermogravimetric analysis/differential thermal analysis, TG/DTA), and tribological (pin-on-disc; SKD-11 pin against AA6061 disc) characterizations were conducted. The biolubricant showed near-Newtonian behavior and viscosity decreased with increasing temperature and with TiO2 addition. TG/DTA showed improved early-stage thermal resistance with TiO2 (20–400 °C mass loss decreased from 23.98% to 16.73%), while the DTA exotherm shifted from 490.46 °C to 284.59 °C. Tribologically, the average coefficient of friction (n=5) decreased from 0.471 (dry) to 0.231 (biolubricant) and 0.131 (biolubricant+TiO2). Wear was markedly reduced: compared with the biolubricant without TiO2, adding TiO2 decreased disc mass loss from 0.0046 g to 0.0020 g and reduced specific wear rate from 0.000341 to 0.000148 mm3/N·m (≈56.6% reduction). Relative to dry contact, the TiO2-enhanced biolubricant reduced mass loss and specific wear rate by ≈92.8%. Overall, the TiO₂-enhanced WCO-based biolubricant is promising for aluminum-related metalworking and other Al–steel sliding interfaces under moderate operating conditions. © 2026 Published by Faculty of Engineering.
Department of Mechanical and Industrial Engineering, Universitas Negeri Malang, Indonesia; Nanomaterials Engineering Research Center, Universitas Negeri Malang, Indonesia; Research Center for Advanced Materials, National Research and Innovation Agency (BRIN), Indonesia; Department of Computing, Faculty of Engineering Science and Technology, Infrastructure University Kuala Lumpur, 43000, Malaysia; Department of Mechanical Engineering, University of Abuja, Abuja, Nigeria
