ARS | Publication request: Synthesis and physical properties of new estolide esters

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2013
Publication Date: March 16, 2013
Citation: Cermak, S.C., Bredsguard, J.W., John, B.L., Mc Calvin, J.S., Thompson, T., Isbell, K.N., Feken, K.A., Isbell, T., Murray, R.E. 2013. Synthesis and physical properties of new estolide esters. Industrial Crops and Products. 46:386-391.

Interpretive Summary: Vegetable oils usually fail to meet the rigorous demands of industrial lubricants by not having acceptable low temperature properties. These low temperature properties can be as simple as what temperature these materials stop pouring or what temperature cloudiness starts to form in the oil. High cloud points of oils in your engine lead to pumpability problems. Having a green bio-based industrial fluid that has good cold weather properties would be highly desirable. A series of new compounds, estolide esters, were developed to help maximize low temperature properties of the oil. On a cold winter day, water freezes at 0 deg C but you don’t want your engine oils and lubricants also freezing at these temperatures; thus, you need advanced materials that will perform well at temperatures below freezing. We have synthesized new estolide materials that have pour points of -24 deg C to -39 deg C compared to 0 deg C for water. The cloud points that were found (ranging from -30 deg C to <-50 deg C) were even better than current commercial petroleum oils (6 deg C to -3 deg C). These new estolide esters required no additives in order to obtain the improved low temperature performance, thus limiting our impact on the environment and helping reduce our dependence on foreign oil.

Technical Abstract: Vegetable oil-based oils usually fail to meet the rigorous demands of industrial lubricants by not having acceptable low temperature properties, pour point (PP) and/or cloud point (CP). The oleic estolide was esterified with a series of 16 different alcohols that were either branched or straight-chained. The new estolide esters physical properties were recorded and evaluated as a potential industrial lubricant. The straight-chain esters had higher low temperature properties (PP = -9 deg C to -33 deg C) but still compete well with other commercial bio-based materials. The oeic estolide ethyl ester yielded the best PP at -33 deg C for the straight-chain series. The branched alcohol produced the best PP (-24 deg C to -39 deg C) and CP (-30 deg C to <-50 deg C) with the best PP performers being a 2-hexyldecanol (Jarcol I-16) sample, a long 16 carbon-chained branched material, and 2-octyldodecanol (Jarcol I-20), a 20 carbon branched material, with a PP at -39 deg C. The best CP performers from the same series were the 2-octyldodecanol, with a CP lower than -50 deg C followed by the 2-hexyldecanol at -42 deg C. The viscosities (55-209 cSt @ 40 deg C) and viscosity indexes (VIs) (169-192) performed well as expected. The iso-stearyl alcohol (Oxocol 180) sample had the highest viscosity at 40 deg C of 209.3 cSt which was higher than all other materials tested. Finally, these new estolide esters required no additives in order to obtain the improved performance in low temperature physical properties, thus limiting our impact on the environment and helping reduce our dependence on foreign oil.