Engineering Green Lubricants II: Thermal Transition and Flow Properties of Vegetable Oil-Derived Diesters

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• 作者：Latchmi Raghunanan ; Suresh S. Narine
• 刊名：ACS Sustainable Chemistry & Engineering
• 出版年：2016
• 出版时间：March 7, 2016
• 年：2016
• 卷：4
• 期：3
• 页码：693-700
• 全文大小：456K
• ISSN：2168-0485

文摘

Six homologous series of linear aliphatic diesters were prepared from commonly available fatty acids (chain lengths 10–22 carbons) and diols (chain lengths, n, 2–10 carbons). The thermal transition and flow properties are presented as functions of their molecular structures, namely chain length, symmetry, end group interactions, and saturation. Predictive relationships between the total chain length of the diesters and their characteristic thermal transition temperatures were obtained. The thermal transition temperatures were affected by intramolecular steric repulsion of the ester groups at small diol chain lengths (n ≤ 4) and by the odd–even effect associated with large diol chains (n > 4), allowing for further refinement of the crystallization and melting prediction models. All of the diesters presented Newtonian flow behavior above their melting points, making them particularly suitable for use in lubricant formulations and other flow-dependent applications. The influence of mass on the viscosity was significantly greater than any other structural feature of the linear aliphatic molecules. Viscosity scaled predictably with total chain length, from ∼6 mPa·s for the smallest diester to ∼41 mPa·s for the largest diester at 40 °C. This range is significantly larger than that accessible to native vegetable oils (33–66 mPa·s at 40 °C), affording a vastly improved application range for biobased materials.