Synthesis and Physical Properties of Hempseed and High-Oleic Hempseed Oil Estolides

Hempseed oil (HSO) bears the unique property of its fatty acid profiles being unusually rich with polyunsaturated fatty acids. While the presence of numerous olefins would make this oil prone to oxidation, the presence of this functional group can be exploited to form oligomers called estolides, improving their oxidative stability and cold flow properties. In this work, a series of estolides were synthesized from HSO and high-oleic HSO (HOHSO) which are capped with fatty acids of varying chain length and esterified with 2-ethylhexanol (2-EH). The estolides capped with shorter chain saturated fatty acids (C8–C14) exhibited excellent cold flow properties, with pour points of −36°C and lower. Estolides prepared from HSO had higher kinematic viscosities than those prepared from HOHSO. HOHSO estolides bore physical properties similar to estolides synthesized from oleic-rich oils, which is advantageous for applications as bio-based motor oils. Furthermore, the HSO/2-EH estolide capped with a shorter chain fatty acid of the series synthesized (specifically caprylic/octanoic acid, C8:0) bore an unusually high kinematic viscosity compared to the rest of the series capped with longer chain fatty acids.