The tribological performance of bio-based room temperature ionic liquid lubricants: A possible next step in biolubricant technology

Historically, biolubricants have evolved from natural oils derived from vegetables to currently used bio-based synthetic room temperature ionic liquids (ILs) that represent a possible next step in biolubricant technology. Natural oils have been used since antiquity due to their high lubricity. As industrial applications become more complex, a desire for more sophisticated lubricants was satisfied with the advent of polyalphaolefins and synthetic ethers. Currently, room temperature ionic liquid lubricants derived from bio-based feedstock represent a promising potential solution to many of the problems associated with previous biolubricants. In this study, the tribological performance of ionic liquids and other comparative lubricants were investigated using a pin-on-disk tribometer under ambient and high temperature conditions. Additionally, a thermogravimetric analysis and an electrochemical corrosion study were performed to investigate the thermal stability and corrosion resistance respectively. The results indicated that the ionic liquids demonstrated improved tribological properties that were equivalent to or superior to conventional petroleum-based and bio-based lubricants due to their unique dipolar structure. When compared to natural oils, the ILs exhibited low rates of thermal degradation at high temperatures, demonstrating their enhanced thermal stability while also maintaining low friction and wear properties. The ionic liquids also exhibited superior corrosion resistance with multiple metals. The many advantages of ILs particularly their negligible vapor pressure and their variety of tunable properties relevant to tribological behavior indicate that ionic liquids offer tremendous potential as a viable alternative to conventional biolubricants.