Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2002
Publication Date: 9/1/2002
Citation: CERMAK, S.C., ISBELL, T. PHYSICAL PROPERTIES OF SATURATED ESTOLIDES AND THEIR 2-ETHYLHEXYL ESTERS. INDUSTRIAL CROPS AND PRODUCTS. 16:119-127. 2002. Interpretive Summary: Have you ever wondered why your car or SUV is able to start in the middle of winter? Most of the automobiles today are probably using petroleum-based lubricants and fluids, ie. crank case oil and power steering fluid, along with additive packages which help make these petroleum-based products work in cold weather applications. The current problem with these petroleum products that we use today is they still do not meet the cold temperature properties needed to help keep your automobile trouble free during the winter months. These petroleum products also leak from our automobiles, contaminating groundwater supplies and killing the fish in our favorite lakes, which makes the environment messy. 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 trying to create these new biodegradable, vegetable-based lubricants and fluids from estolides which are easier on animals and plants 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, to make estolides. Estolides are therefore a renewable U.S.-based crop oil that will help ease the dependence on imported, petroleum-based oils.
Technical Abstract: Biodegradable, vegetable oil-based lubricants must have better low temperature properties before they can become widely acceptable in the marketplace. These low temperature properties are usually measured as the material's pour point, the minimum temperature at which a material will still pour. Viscosity and viscosity index also provide information about a fluid's properties where a high viscosity index denotes that a fluid has little viscosity change over a wide temperature range. Oleic acid and a series of saturated fatty acids, butyric through stearic, were treated with 0.4 equivalents of perchloric acid at either 45 C or 55 C to produce complex estolides. Yields varied between 45-65% after Kugelrohr distillation. The estolide number (EN), the average number of fatty acid units added to a base fatty acid, varied with reaction temperature as well as with the change in saturated fatty acids. The saturate-capped, oleic estolides were esterified with 2-ethylhexanol to obtain high yields of the corresponding ester. As the chain length of saturate capping material increased from C-4 to C-10, the low temperature performance of the estolide 2-ethylhexyl esters, namely pour point, decreased to -39 C. The other mid-chain, saturated estolide 2-ethylhexyl esters C-6 through C-14 also had superior low temperature properties when compared to their competitors: soy-based, synthetic-based and petroleum-based oils. These new estolide esters have displayed far superior low temperature properties, and were more suitable as a base stock for biodegradable lubricants and functional fluids.