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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Bio-oils Research » Research » Publications at this Location » Publication #287716
Title: Synthesis of polyformate esters of vegetable oils: Milkweed, pennycress and soy

Author
item Harry O Kuru, Rogers
item Biresaw, Girma
item Tisserat, Brent
item Evangelista, Roque

Submitted to: Journal of Lipids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2015
Publication Date: 2/4/2016
Citation: Harry O Kuru, R.E., Biresaw, G., Tisserat, B., Evangelista, R.L. 2016. Synthesis of polyformate esters of vegetable oils: Milkweed, pennycress and soy. Journal of Lipids. 1-12.

Interpretive Summary: Modified vegetable oils are rapidly playing increasing roles as biofuels and biolubricants following the awareness of their inherent renewability and biodegradability. In this regard, data obtained from our previous modification work on Milkweed oil seemed to suggest that the presence of short pendant chains on the oil structure would improve the lubricating properties of the derivatized oil in comparison to longer pendant chains. To verify this hypothesis, we have chemically modified the oil chains by placing many very short chain length stubs on the chains of three different vegetable oils in order to assess any induced changes to the character of these oils, vis-a-vis the parents and those with longer pendant chains. In this communication, we report the development of novel biobased materials (milkweed, soy, and pennycress-modified oils) that exhibit excellent lubricating characteristics, thus confirming the aforementioned hypothesis.

Technical Abstract: In a previous study of the characteristics of acyl derivatives of polyhydroxy milkweed oil (PHMWO), it was observed that the densities and viscosities of the respective derivatives decreased with increased chain length of the substituent acyl group. Thus from the polyhydroxy starting material, attenuation in viscosity of the derivatives relative to PHMWO was found in the order: PHMWO >> PAcMWE >> PBuMWE >>PPMWE (2332:1733: 926.2: 489.4 cSt, respectively, at 40 deg C) where PAcMWE, PBuMWE, and PPMWE were the polyacetyl, polybutyroyl, and polypentanoyl ester derivatives, respectively. In an analogous manner, the densities also decreased as the chain length increased although not as precipitously compared to the viscosity drop. By inference, derivatives of vegetable oils with short chain length substituents on the triglyceride would be attractive in lubricant applications in view of their higher densities and possibly higher viscosity indices. Pursuant to this, we have explored the syntheses of formyl esters of three vegetable oils in order to examine the optimal density, viscosity, and related physical characteristics in relation to their suitability as lubricant candidates. In the absence of ready availability of formic anhydride, we opted to employ the epoxidized vegetable oils as substrates for formyl ester generation using glacial formic acid. The epoxy ring-opening process was smooth but was apparently followed by a simultaneous condensation reaction of the putative alpha-hydroxy formyl intermediate to yield vicinal diformyl esters from the oxirane. All three polyformyl esters (milkweed, soy, and pennycress derivatives) exhibited low coefficient of friction and a correspondingly much lower wear scar in the 4-ball antiwear test compared to the longer chain acyl analogues earlier studied.