Synthesis and Tribological Analysis of Ionic Liquid-Based BioLubricants

Abstract

Purpose. Lubrication is inevitable for all interacting surfaces in IC engines to avoid component failure and reduce frictional losses specifically operating under boundary lubrication regime. Environmental concerns, decreasing mineral oil reserves and difficult disposal of nonbiodegradable conventional lubricants have urged the researchers to shift towards environmental-friendly lubricants. In this article compatibility of various ionic liquids with different bio-lubricants and conventional lubricants regarding their tribological performance has been studied and compared. Methodology. In this study two potassium based ionic liquids including Bis(2-ethylhexyl) phosphate and Trihexyltetradecylphosphonium bis(2,4,4- trimethylpentyl) phosphinate have been checked for their compatibility towards bio-lubricants including Cotton seed oil, Waste cooking oil, Rattan Jot oil and polyalphaolefin (PAO) etc. The physicochemical properties including viscosity, density, viscosity index, kinematic viscosity, flash point, pour point, total acid number (TAN) and total base number (TBN) of bare oils and their blends with ionic liquids were investigated using different ASTM standards Findings. Trihexyltetradecylphosphonium bis(2,4,4 trimethylpentyl) phosphinate were completely soluble in the base oils and are assumed to exhibit better tribological performance. Value. Ionic liquids are excellent solvents and are easily miscible in bio-lubricants and therefore can be used as additive with minor modifications. They produce less ash content and hence are environment friendly. IL-based bio-lubricants have the tendency to replace conventional lubricants regarding their tribological applications. However, further work on improving bio-lubricant’s wear characteristics is needed for complete replacement of mineral oil-based lubricants.