Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 6, 2008
Publication Date: June 20, 2008
Citation: Cermak, S.C., Biresaw, G., Isbell, T. 2008. Comparison of a New Estolide Oxidative Stability Package. Journal of the American Oil Chemists' Society. 85(9):879-885. Interpretive Summary: As new technologies are developed, we are charged with the task to get those technologies into the hands of industrial partners. Sometimes these recent developments need additional work or modifications to make them more appealing. Estolides are a technology that was previously created at the Peoria Lab that had commercialization difficulties. As scientists, we must understand the shortfalls of a given technology and be able to conduct additional research to get these technologies to the marketplace. Estolides have excellent physical properties, performing well under controlled test conditions, but they still need a little help. Additive packages are one cure to help oils obtain better physical properties. The estolides required an oxidative stability package to exceed motor oil currently in the marketplace. Different oxidative stability packages are available from formulators, but they are usually expensive and are not designed specifically for estolides. Our goal was to examine different types of oxidative stability package additives and formulate our own for a series of different estolides. The formulated estolides were evaluated for their ability to resist oxidation or breakdown when exposed to air, as measured by the rotating pressurized vessel oxidation test (RPVOT) and compared to commercial products. We were able to develop a new oxidative stability package for the estolide series that exceeds what is currently available on the market and give the estolide technology an advantage in its commercialization.
Technical Abstract: The use of the rotating pressurized vessel oxidation test (RPVOT) was instrumental in the analysis and determination of a new antioxidant package for a series of estolide-based materials. Three antioxidants (BHT, Lanlube NA and Lanlube SL) were used in either 0.5 or 1.0 wt/wt %, in different ratios, and in conjunction with one another (BHT/Lanlube NA or BHT/Lanlube SL). The estolide-based samples analyzed for their resistance to oxidation were two pure estolides (oleic estolide 2-EH esters and coco-oleic estolide 2-EH esters), an estolide mixture that was analyzed straight from the reaction (coco-oleic estolide 2-EH esters with coco 2-EH esters) and, finally, the ester fraction from the estolide mixture (coco 2-EH esters). The coco estolide mixture and coco 2-EH esters had the best overall RPVOT times, coco estolide mixture, 326 mins, with 1.0% of the Vanlube NA, and coco 2-EH esters, 310 mins, with 1.0% of the Vanlube NA. Coco estolides were expected to have an advantage over the simple oleic estolides due to the increase in saturation in the estolide. Unexpectantly, the two pure estolides (oleic and coco) had very similar RPVOT max times with all the antioxidants and were much higher than when tested with other oxidative packages tested to date. Vanlube NA outperformed Vanlube SL in the majority of the ratios tested. Overall, a series of new antioxidants were tested and compared to other commercial products. A variety of physical properties of the four estolide-based material were collected and compared to commercially acceptable material. Coco-oleic estolide 2-EH esters were formulated to have excellent pour points (-36 deg C), were both oxidatively and hydrolytically stable (RPVOT, 310 mins), with expected good biodegradability, which should help commercialization.