Modified Ionic Liquid-Based High-Performance Lubricants for Robotic Operations
Hess, David M.
InnoSense LLC (ISL) has developed modified ionic liquid-based low temperature lubricants for use in NASA robotic systems. Ionic liquids are known to exhibit a much lower coefficient of friction in comparison to traditional lubricants, operate within a wide temperature range and exhibit low volatility. As a result, lubricants based on ionic liquids reduce the risk of damage to critical space-based hardware. In this paper, we present our latest work developing a method for using pyridinium salts to control thermal stability though phase modulation and to improve lubricity. This phase modulation results in lower melting points and possibly improved metallic surface interactions. Our results for this method have suggested that the modified ionic liquid lubricant exhibits a highly ordered structure that forms a boundary layer at the metallic surface through electrostatic interactions. This microscopic alignment provides for excellent lubricity through the repulsive and attractive interactions between molecules. The ionic liquid lubricant system, thus exhibits a higher degree of general performance than traditional liquid lubricants. We have tested the physical phase properties of the lubricant in temperatures ranging from –90 °C to 300 °C. Our lubricant does not corrode metallic substrates, phase separate, or degrade. In preliminary side-by-side ball bearing performance testing conducted at the ISL facility, our modified ionic liquid lubricants outperformed stock lubricants (preloaded bearing hydrocarbon-based lubricant). Our system exhibited lower driving currents with little sign of wear. Ongoing work is being performed to demonstrate the low temperature limit of the lubricant in field appropriate conditions.