|Cermak, Steven - Steve
|BREDSGUARD, JAKOB - Biosynthetic Technologies
|Dunn, Robert - Bob
|THOMPSON, TRAVIS - Biosynthetic Technologies
|FEKEN, KATI - Biosynthetic Technologies
|ROTH, KATIE - Biosynthetic Technologies
|Kenar, James - Jim
Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2014
Publication Date: 11/24/2014
Publication URL: http://handle.nal.usda.gov/10113/60461
Citation: Cermak, S.C., Bredsguard, J.W., Dunn, R.O., Thompson, T., Feken, K.A., Roth, K.L., Kenar, J.A., Isbell, T.A., Murray, R.E. 2014. Comparative assay of antioxidant packages for dimer of estolide esters. Journal of the American Oil Chemists' Society. 91:2101-2109.
Interpretive Summary: A major success story for ARS for the past two years has been estolides. However, the estolide technology still requires some advance tweaking to truly optimize its full potential. Estolides are a biobased functional fluid that was developed at the National Center for Agricultural Utilization Research in Peoria, IL, and is currently undergoing commercialization. As scientists, we must understand the shortfalls of a given technology and be able to conduct additional research to help get these technologies to the marketplace. Estolides have been proven to have excellent physical properties; however, as motor oil standards increase, changes have to be made. Additive packages are one technique to help oils obtain better physical properties, i.e. performance. The estolides require a commercial oxidative stability package to meet current stantands needed for motor oil applications. Our goal was to examine a series of different types of oxidative stability package additives on the commercial estolide. The formulated estolides were evaluated for their ability to resist oxidation or breakdown when exposed to air, as measured by the pressurized differential scanning calorimeter (P-DSC. We were able to identify some potential useful oxidative stability packages for the estolides that meet what is currently available on the market as well as give the estolide technology an advantage to its commercialization.
Technical Abstract: A series of 26 different antioxidants and commercial antioxidant packages, containing both natural and synthetic-based materials, were evaluated with dimeric coconut-oleic estolide 2-ethylhexyl ester. The different antioxidants were broken down into different classes of materials: phenolic, aminic, blended/others. The oxidation onset temperatures (OTs) using non-isothermal pressurized differential scanning calorimetry (P-DSC) were measured and recorded under standard method conditions previously reported. The aminic series gave the best resistance to oxidation as defined by the P-DSC method with OTs of 246.6 and 244.7 deg C for the best performers which was about a 17-19% increase over the uninhibited or unformulated dimer estolide material. The phenolic series was the least successful formulation package for the dimer estolide. The phenolic series contained most of the naturally occurring antioxidants. The blended/other materials, which were material specifically designed for lubricants, did not have the best OTs. Many of these materials were designed for petroleum-based materials and the estolides and other bio-based materials interact differently than their petroleum counterparts. A number of potential new antioxidants have been identified as possible additives with the estolides esters. The OTs of the estolide and formulated materials correlated well with other bio-based materials such as biodiesel.