Concentration Dependence of the Viscosity Activation Energy of Aqueous Ethylene Glycol Mixtures

Abstract

Mixtures of ethylene glycol with water are a prominent example of media with variable viscosity, and ethylene glycol molecules serve as a prototype of various polyols having multiple hydroxyl groups. The dynamic viscosity of ethylene glycol–water mixtures was measured by vibro-viscosimetry over entire range of mole fraction under atmospheric pressure and from 10 to 30 °C; the variation of the viscosity activation energy with ethylene glycol mole fraction was determined and is discussed. In the present work we propose a novel equation for modeling the concentration dependences of the activation energy and viscosity. The theory is based on the assumption that the nonlinear characteristics can be associated with some structural changes of the mixtures, and that the reaction kinetics can be applied to this breakdown. The Grunberg–Nissan parameter and viscosity deviations were calculated. The possible changes in the variety of complexes for different concentration ranges is discussed. Correlation between the activation energy and pre-exponential factor was made. Three concentration regions are determined, separated by ethylene glycol molar fractions x = 0.11 and 0.43, where the structure of the water/ethylene glycol complexes changes.