Synthesis and Physical Properties of Tallow-Oleic Estolide 2-Ethylhexyl Esters

Tallow-oleic estolide 2-ethylhexyl (2-EH) esters were synthesized in a perchloric acid catalyzed one-pot process from industrial 90% oleic and tallow fatty acids at various ratios, while varying the ratio of tallow and oleic fatty acids, with the esterification process incorporated into an in situ second step to provide a functional fluid. Their viscosities ranged 57–80 cSt at 40 °C and 10.8–14.0 cSt at 100 °C with viscosity index (VI) 169–185. The 100% tallow estolide 2-EH ester had modest low-temperature properties (pour point = −15 °C and cloud point = −14 °C), while the 50:50 mixture of oleic and tallow fatty acids produced an estolide that had better low-temperature properties (pour point = −21 °C and cloud point = −21 °C) without a large negative effect on the oxidative stability. The oxidative stability increased as the amount of saturation increased (rotating pressurized vessel oxidation test (RPVOT) × 165–274 min). The tallow-oleic estolide 2-EH esters have shown remarkably low evaporative losses of only 1% loss compared to a 15–17% loss for commercial materials of similar viscosity grade. Along with expected good biodegradability, these tallow-oleic estolide 2-EH esters had acceptable properties that should provide a specialty niche. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.