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A new series of pennycress ( Thlaspi arvense L.) based free-acid estolides was synthesized by an acid-catalyzed condensation reaction, followed by an esterification reaction to produce the 2-ethylhexyl (2-EH) esters of the initial estolides. The physical properties of the estolides are highly affected by the length and unsaturation level of the capping fatty acid, the base fatty acid unit, and estolide linkage position. Both the free-acid estolides and the estolide 2-EH esters produced proved to have marked viscosity increases over previously synthesized estolides. Kinematic viscosities of the free-acid estolides were higher than the corresponding estolide 2-EH esters, ranging from 494.4 cSt to 870.5 cSt at 40 °C and 53.6 to 75.3 cSt at 100 °C with viscosity indices (VI) from 134 to 163. Viscosities of the estolide esters ranged from 116.3 to 245.75 cSt at 40 °C and 18.2 to 33.6 cSt at 100 °C with viscosity indices (VI) from 169 to 183. The highest viscosity values belonged to the pennycress estolides made with pennycress fatty acids in the reaction acting as the base material, as well as the capping material. The oleic capped pennycress estolide 2-EH esters had the best low-temperature properties with a pour point (PP) of −33 °C and cloud point (CP) of −31 °C. With the exception of palmitic acid, there was very little variation in the low-temperature properties of the remaining saturate capped estolide 2-EH esters, PP ranging from −18 to −21 °C. Pennycress is currently being developed for green diesel applications; the development of other industrial applications is a necessity for the success of an alternative crop. The combination of high viscosity and modest cold temperature properties of these pennycress estolides could fill a specialty niche as a high viscosity industrial lubricant. [ABSTRACT FROM AUTHOR]

Abstract: A new series of petroselinic (Coriandrum sativum L.) based estolide 2-ethylhexyl (2-EH) esters were synthesized, as the capping material varied in length and in degrees of unsaturation, in a perchloric acid catalyzed one-pot process with the esterification process incorporated into an in situ second step to provide the coriander estolide 2-EH ester. The kinematic viscosities ranged from 53 to 75 cSt at 40°C and 9.1 to 14.6 cSt at 100°C with a viscosity index (VI) ranging from 151 to 165. The caprylic (C8) capped coriander estolide 2-EH ester had the lowest low-temperature properties (pour point=−33°C and cloud point=−33°C), while the coco-coriander estolide 2-EH ester produced an estolide with modest low-temperature properties (pour point=−24°C and cloud point=−25°C). The coco-coriander estolide 2-EH ester was explored for the ability to resist oxidative degradation with the use of an biodegradable additive package added in 1.5%, 3.5%, or 7.0% units based on weight. The oxidative stability increased as the amount of stability package increased (rotating pressurized vessel oxidation test (RPVOT) times 65–273min). Along with expected good biodegradability, these coriander estolide 2-EH esters had acceptable properties that should provide a specialty niche in the U.S. as a biobased lubricant. [ABSTRACT FROM AUTHOR]

Abstract: Saturated mono-estolide methyl esters and enriched saturated mono-estolide 2-EH esters were synthesized from oleic and different saturated fatty acids under three different synthetic routes. Estolide numbers (EN), the average number of fatty acid units added to a base fatty acid, varied with synthetic conditions. The attempts at obtaining saturated mono-estolide 2-EH esters, EN=1, via distillation proved to be challenging, which lead to estolide samples with EN>1 and the pour point values followed the same trend as the high EN estolides. The other synthetic routes provided saturated mono-estolide methyl esters with EN=1. The resulting pour point values showed a linear relationship between the saturated capping chain length and pour point. As the saturated capping chain length increased the pour points also increased (higher temperatures): C-2 capped −30°C, C-10 capped −12°C, and C-18 capped 3°C. The saturated mono-estolide methyl ester viscosities also showed an increase in viscosity at 40 and 100°C as the saturated chain lengths increased. The viscosities for the C-4 saturated mono-estolide methyl ester was 9.5 cSt at 40°C and 2.6 cSt at 100°C, while medium chain length derivations (C-10 saturated mono-estolide methyl ester) were 19.7 cSt at 40°C and 4.2 cSt at 100°C, and at the longer chain length derivations (C-18 mono-estolide methyl esters) were 27.6 cSt at 40°C and 10.7 cSt at 100°C. In general, a new series of saturated oleic mono-estolide methyl esters were synthesized and physical properties were collected. The physical property data indicated that both chain length and EN affect low temperature properties. [Copyright &y& Elsevier]

Abstract: Biodegradable, vegetable oil-based lubricants must have better low temperature properties as well as comparable cost to petroleum oils before they can become widely acceptable in the marketplace. The low temperature property usually measured is the pour point (pp), the minimum temperature at which the 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. Lesquerella oil is a good candidate for its development into a biodegradable lubricant as it is being developed as an alternative crop for the southwestern U.S. The hydroxy site on the fatty acid (FA) makes it a suitable site for esterification to yield estolides. Castor and lesquerella FA esters were combined with different types of saturated, unsaturated, and branched FAs to produce estolides. Castor and lesquerella estolide esters had the best cold temperature properties when capped with oleic (pp=−54°C for castor and pp=−48°C for lesquerella) or capped with a branched material, 2-ethylhexanoic acid (pp=−51°C for castor and pp=−54°C for lesquerella). As the saturation was increased in the estolide, pour and cloud points also increased. The increased saturation such as in stearic capped estolides allowed for sufficient alkyl stacking of these long saturated chains producing higher pour points. Oxidative stability of the estolides was compared between the oleic-castor estolide 2-ethylhexyl ester and the coco-castor estolide 2-ethylhexyl ester by the rotating bomb oxidation test (RBOT). The RBOT times for both estolides were low with a similar time of about 15min. However, when the antioxidant package (3.5wt.%) was added, the RBOT times increased to 403min for the coco-castor estolide 2-ethylhexyl ester while still retaining its outstanding cold temperature properties, (pp=−36°C and cp=−30°C). The viscosity index ranged from 164 to 200 for these new hydroxy FA derived estolide 2-ethylhexyl esters. These oleic-castor and lesquerella estolide esters have displayed far superior low temperature properties (pp=−54°C) than any other estolides reported to date. Due to the lack of solvent and catalysts, the cost of these estolides should be reasonable and more suitable as a base stock for biodegradable lubricants and functional fluids than current commercial materials. [Copyright &y& Elsevier]

Biodegradable, vegetable oil-based lubricants must have better low temperature properties as well as comparable cost to petroleum oil before they can become widely acceptable in the marketplace. These include low pour point temperature, low viscosity and viscosity indices that do not change over a wide temperature range. Our objective was to synthesize estolides from various sources with improved lubricating physical properties. Oleic acid and lauric acid were treated with varying equivalents of perchloric acid at 60 °C to produce complex estolides. Yields ranged between 45 and 75% after purification by Kugelrohr distillation. The estolide number (EN), the average number of fatty acid units added to a base fatty acid, varied with reaction conditions. The saturate-capped, oleic estolides were esterified with 2-ethylhexanol to obtain high yields of the corresponding ester. Coconut–oleic 2-ethylhexyl estolide esters were produced by varying the ratio of oleic and coconut fatty acids with 0.05 equivalents of HClO4 to give estolides with excellent cold temperature properties. The amount of oligomerization (EN) played an important role on viscosity; 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 141 to 170 for the free acid estolides, whereas the complex estolide 2-ethylhexyl esters had slightly higher viscosity indices, which ranged from 159 to 232. These new coco–oleic estolide esters displayed superior low temperature properties (−36 °C), were of reasonable cost, and were more suitable as a base stock for biodegradable lubricants and functional fluids than current vegetable oil-based commercial materials. [Copyright &y& Elsevier]

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 or 55 °C to produce complex estolides, dimers and tetramers of fatty acids linked through the double bond and carbonyl group. Yields varied between 45 and 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 compared with their competitors; i.e. soy-based, synthetic-based and petroleum-based oils. The amount of oligomerization (EN) had an important role with the viscosities. Viscosity increased with higher oligomerization and the free acid estolides were generally several hundred centistokes (cSt) more viscous than the corresponding esters. The viscosity index ranged from 122 to 155 for the free acids estolides while the estolide 2-ethylhexyl esters had slightly higher indices which ranged from 172 to 196. These new estolide esters displayed far superior low temperature properties, and were more suitable as a base stock for biodegradable lubricants and functional fluids than current commercial materials. [Copyright &y& Elsevier]

Abstract: Lesquerella is a developing hydroxy oilseed crop suitable for rotation in the arid Southwestern United States. The hydroxy oil of lesquerella makes it suitable for esterification into triglyceride estolides. The estolide functionality imparts unique physical properties that make this class of materials suitable for functional fluid applications. Lesquerella and castor hydroxy triglycerides were converted to their corresponding estolides by reacting the oils with saturated fatty acids (C2–C18) in the presence of a tin 2-ethylhexanoate catalyst (0.1wt.%) and utilizing the condensation of hydroxy with corresponding anhydride or heating under vacuum at 200°C. Two homologous series of estolides for each triglyceride were synthesized for comparison, mono-capped (one hydroxy functionality per triglyceride molecule) and full-capped (all hydroxy functionalities per triglyceride molecule). Physical properties (pour point, cloud point, viscosity, and oxidative stability) were compared for this estolide series. The longer chain saturate capped estolides (C14–C18) had the highest pour points for both mono-capped (9°C, C18:0) and full-capped (24°C, C18:0) lesquerella estolides. Castor mono-capped (9°C) and full-capped (18°C) triglyceride estolides gave similar properties. However, pour points improved linearly when the shorter saturated fatty acid capping chain lengths were esterified with the hydroxy triglycerides. Lesquerella capped with a C6:0 fatty acid had pour points of −33°C for the mono-capped and −36°C for the full-capped and castor had −36 and −45°C, respectively. Oxidative stabilities of the estolides were compared for oleic, lauric and lauric-hydrogenated mono- and full-capped materials by rotating bomb oxygen test (RBOT). RBOT times for oleic and lauric capped estolides were low and similar with times centered around 15min. However, when antioxidant (4wt.%) was added the RBOT times increased to 688min for the hydrogenated full-capped lesquerella lauric estolide. The antioxidant had little effect on RBOT times when 2wt.% or less antioxidant was added for all the estolides except those that were hydrogenated. The hydrogenated estolides showed improvements in oxidative stability at all concentrations of antioxidant tested. Viscosity index ranged from 130 to 202 for all estolides with the shorter chain length capped estolides gave the lower viscosity index values. Viscosity at 100°C ranged from 13.9 to 26.6 cSt and the 40°C viscosity ranged from 74.7 to 260.4 cSt where the longer chain length capped estolides gave the highest viscosities. [Copyright &y& Elsevier]