The N,N-dimethylformamide + 2-methoxyethanol binary mixtures. Viscosity and activation energy of viscous flow at various temperatures

Dynamic viscosity (eta) of binary solvent mixtures of N,N-dimethylformamide (DMF, component 1)+ 2-methoxyethanol (ME, component 2) has been investigated at 19 temperatures ranging from -10 to +80 degrees C. Some empirical equations have been applied in order to establish the best regression fitting procedures eta=eta(T), eta=eta(X(1)) and eta=eta(T,X(1)). For this binary solvent system, the viscometric properties are continuous but not linear functions of the mixture composition. Therefore, experimental eta values were used to calculate the excess viscosities (eta(E)) and excess Gibbs activation energies (Delta G*(E)) of viscous flow. Both these quantities strongly deviate from ideality over the whole composition range of the investigated mixtures. Furthermore, deviations from the ideal behaviour could be very useful in order to evidentiate the formation of solvent-cosolvent complex species and to evaluate their stoichiometrical composition.