Study of the effect of chemical structure of esters and vegetable oils on friction and wear with and without wear additives

Friction and wear of materials occur in all mechanical systems and improved friction and wear performance can lead to greater efficiency. This work studies the effect of chemical structure of esters and vegetable oils on friction and wear with and without lubricant additives. One objective includes modeling the base fluid's wear and friction results based on chemical structure. The thesis then compares the wear model to the current non-polarity index model, which does not account for most chemical structure effects. The other main objective includes determining if chemical structures of the base stocks still affect wear and friction after addition of various anti-wear additives. To accomplish the objectives, the author uses a four-ball test machine to measure friction and wear along with statistical programs to determine important chemical structure factors. Later the author used scanning electron microscopy and X-ray energy dispersive spectroscopy to examine the wear scars and debris. The thesis presents a wear index model, which showed a much better fit than the current non-polarity index model. For a logarithmic fit, the wear index model increased the R2 by about 40%. While the wear index model shows improvement over the current non-polarity index model with the tested data, outside data also shows that the model does not appear to work any better than the current model with diesters. The testing also showed that even after the addition of anti-wear additives the base fluid chemical structure still affected wear. Only Additive B eliminated chemical structure effects when looking at friction and wear. The author also found that with the same additive the presence of unsaturation in the base fluid could lead to different additive mechanisms to protect the surface. Since the base fluid affects wear and friction performance, lubricant formulators should consider the base fluid's chemical structure when developing lubricants.