Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/9/2003
Publication Date: 3/11/2004
Citation: Cermak, S.C., Isbell, T. 2004. Synthesis and physical properties of cuphea-oleic estolides and esters. Journal of the American Oil Chemists' Society. 81:297-303. Interpretive Summary: The current problem with most petroleum and vegetable based products that we use today is they still do not meet the cold temperature properties needed to help keep your machinery trouble free during the winter months. There is a serious need for biodegradable, vegetable-based lubricants and fluids that have excellent low temperature physical properties for winter conditions without the addition of toxic additive packages. Our lab is creating these new biodegradable vegetable-based lubricants and fluids from estolides which are easier on our environment than petroleum products and have favorable low temperature properties without the addition of additive packages. We mainly use oleic acid from an oil, like cooking oil from sunflower seeds and a new crop called cuphea which is also an oil, to make estolides. Estolides are therefore a renewable U.S.-based crop oil that will help ease the dependence on imported, petroleum-based oils while helping the U.S. farmer.
Technical Abstract: Cuphea-oleic estolides and esters were synthesized from cuphea and oleic fatty acids with various amounts of perchloric acid, 0.01 to 0.40 equivalents, at 60 C. Estolide yields ranged from 30 to 65% after Kugelrohr distillation. Estolide number (EN), the average number of fatty acid units added to a base fatty acid, varied with reaction conditions. Cuphea-oleic estolides were esterified with 2-ethylhexanol to obtain high yields of the corresponding ester. A streamlined, one-pot estolide and its ester were synthesized with 0.05 equivalents of HClO4 with esterification incorporated into an in situ second step to provide a functional fluid at a very reasonable cost. The cuphea-oleic estolides' and estolide esters' physical properties, including viscosities, pour and cloud points, were related directly to the amount of oligomerization (EN) ie; viscosity increased with higher oligomerization. The free acid estolides were generally several hundred centistokes (cSt) more viscous than their corresponding esters. The viscosity index ranged from 132 to 166 for the free acid estolides while the complex estolide 2-ethylhexyl esters had slightly higher viscosity indices that ranged from 165 to 181. Two of the most important physical properties for a functional fluid are the low temperature requirements, pour and cloud points. These new cuphea-oleic estolide esters have displayed good low temperature properties (pp - 42 C and cp -41 C).