Submitted to: Tribology Letter
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 4, 2007
Publication Date: March 8, 2007
Citation: Biresaw, G., Cermak, S.C., Isbell, T. 2007. Film-forming properties of estolides. Tribology Letters. 27(1):69-78. Interpretive Summary: Large surplus of farm products relative to demand have the potential to depress the prices that farmers get for their crops. One way of increasing demand for farm products is by developing new uses in applications currently dominated by petroleum-based products. An example of such application area is in lubrication, where petroleum-based products almost exclusively dominate various lubrication applications including: metalworking, hydraulics, motor oil, etc. However, successful replacement of petroleum-based products by farm-based products requires overcoming certain inherent drawbacks of farm-based raw materials. One way of doing this is synthesizing new lubricants using farm products such as corn and soybean oil as feedstock. One class of products obtained using this approach is estolides. In this work, the film forming properties of estolides were investigated and compared to those of soybean, jojoba, and canola. The result showed that estolides have a superior film forming properties than the seed oils from which they were synthesized. This result demonstrates that the performance of farm products can be improved through modifications and synthesis.
Technical Abstract: Estolides are biobased materials obtained from synthesis of ingredients derived from agricultural products. They are oligoesters obtained by the reaction of fatty acids and/or methyl esters with a double bond. By varying the chemistries of the starting materials and the reaction conditions, estolides of varying chemical structures (e.g., branching), and physical properties (e.g., mol wt, viscosity, pour point, cloud point) are obtained. Estolides have been found to have suitable properties for some lubrication applications. In this work, the effect of estolide physical/chemical variability on film thickness and pressure-viscosity coefficient (pvc) were examined. The results showed that estolides have lower pvc than the non-polar hydrocarbon PAO, but much higher than seed oils (e.g., soybean, jojoba, canola), which are used as feedstock in estolide synthesis. The film thickness and pvc properties of estolides were also found to be dependent on the structure (e.g. homo- vs co-oligomer) and purity of the estolide oils.