Tribological study of imidazolium and phosphonium ionic liquid-based lubricants as additives in carboxylic acid-based natural oil: Advancements in environmentally friendly lubricants

This paper highlights the potential of a new family of environmentally sustainable, functional bio-lubricants called room temperature ionic liquids (RTILs). In this investigation, a tribometer was utilized to carry out friction and wear experiments under ambient conditions to investigate the use of imidazolium and phosphonium-based RTIL's. The study investigated the tribological functionality of RTIL's as additives in plant-based avocado oil and as green sustainable fluids. The use of RTIL as additives in natural oil revealed that a higher percentage mix of RTILs can linearly improve the tribological performance. It was found that, depending on the type and percentage mix of RTIL with avocado oil, the coefficient of friction (COF) could be reduced by as much as 68.88% and the wear volume could be reduced by 73.37%. The RTILs were able to reduce the COF and wear volume not only when used as additives but also when used as base lubricating fluids. It was found that this was a result of the more resilient carboxylate acid-based monolayers that influenced the boundary lubrication regime. The present study details the influence of RTILs as additives, and the role of additive concentration in controlling the tribological performance to aid cleaner production research. Further, the study discusses their future as sustainable lubricants, and their underlying lubrication mechanisms.