Influence of fatty acid additives on the tribological performance of sunflower oil

Vegetable oils are potential substitutes for petroleum-based lubricants because they are environmentally friendly, renewable, less toxic and readily biodegradable. The addition of free fatty acids has been shown to increase the lubrication performance of vegetable oils at elevated temperatures. The purpose of this study was to evaluate the relationship between the length of the carbon chain in the fatty acid and its effectiveness as an additive for a range of elevated temperatures. Stearic, arachidic and behenic fatty acid additives were added to commercial sunflower oil. All fatty acid additives were shown to be effective in lowering the wear rate and coefficient of friction in ball-on-disc tribological tests. The overall carbon chain length was not observed to have a consistent influence on the effectiveness of the additive. All additives were less effective at temperatures above 100°C. Copyright © 2010 John Wiley & Sons, Ltd.