Correlating viscosity of 2-ethylhexyl oleic estolide esters to their molecular weight

Abstract

Estolides are a relatively new class of biobased materials, and their viscosity properties are not thoroughly investigated. The viscosity of thirteen 2-ethylhexyl oleic estolide esters was measured at six temperatures between 20 and 100 °C. The data was fitted with a dozen literature viscosity models. Most of the models were three-parameters models, some were two-parameters, and one was four-parameter. Five of the three-parameter models are theory-based, the rest are empirical. The jackknife procedure was used to estimate the uncertainty of the fitted parameters. The Mauro-Yue-Ellison-Gupta-Allan (MYEGA) model fitted best the experimental data. For the theory-based models, correlations were derived between the fitted coefficients and the molecular weight of the sample. The results allowed for simple prediction of the viscosity of estolide esters as a function of the temperature, based only on number-average molecular weight (or on the estolide number). The best model required additional knowledge of the weight-average molecular weight.