Iso-oleic estolide products with superior cold flow properties

Abstract

One of the drawbacks of using vegetable oils directly as a lubricant is poor low temperature performance, mainly pour and cloud points. Oleic estolides were developed to improve these properties as well as increase the oxidative stability of the oil. However, additional low temperature properties are desirable to increase the field of use of these materials. A new series of iso-oleic estolide free acids and 2-ethylhexyl (2-EH) esters capped with various fatty acids had superior physical properties and cold flow properties, compared to traditional oleic based estolides. The average pour point of the iso-oleic estolide 2-EH esters was − 41°C, compared to − 23°C of iso-oleic estolide free acids. The iso-oleic-octanoic and iso-oleic-decanoic estolide 2-EH esters had excellent pour points of − 60°C. The cold flow properties of iso-oleic estolides decrease with increasing the carbon number of the saturated capping fatty acid, while the viscosity index and oxidation stability were only slightly improved. Therefore, saturated mid-chain fatty acids are more suitable as the capping fatty acid for iso-oleic acid based estolides. Iso-oleic-coconut estolide 2-EH esters exhibited good physical properties, with pour points as low as − 45°C. The iso-oleic estolide free acids and 2-EH esters are a new kind of low-cost materials for bio-lubricants with excellent cold flow properties.