The role of ionic liquid additives in enhancing the tribological performance of plastic-derived oils

Improper disposal of waste plastic contributes significantly to environmental pollution. A promising solution to address this issue involves converting such plastics into valuable lubricating oils. This study investigated the tribological performance of both an aromatic-lean industrial plastic oil (PO) and aromatic-rich lab-scale plastic oils (LPO) using a ball-on-disk setup. The results revealed that PO exhibited considerably higher coefficients of friction (COF) and specific wear rates compared to LPO. To enhance the lubrication performance, a bio-based ionic liquid (IL: trihexyltetradecyl phosphonium saccharinate) with an unsaturated anion was incorporated. The COF and wear rates were further reduced with an IL blend in both PO and LPO. The IL additive promoted increased film thickness, beneficial micelle formation, facilitated adsorption film formation, and provided a phosphorus-rich tribofilm. These mechanisms collectively contributed to the notable improvement in tribological performance. Overall, this research demonstrates the potential of IL additives to enhance the tribological performance of both PO and LPO, thereby mitigating waste plastic pollution, and fostering a sustainable future.