Volumetric and Viscosimetric Measurements for Methanol + CH 3 –O–(CH 2 CH 2 O) n –CH 3 ( n = 2, 3, 4) Mixtures at (293.15–303.15) K and Atmospheric Pressure: Application of the ERAS Model

Densities, $$rho$$, and kinematic viscosities, $$nu$$, have been determined at atmospheric pressure and at 293.15–303.15 K for binary mixtures formed by methanol and one linear polyether of the type CH3–O–(CH2CH2O)n–CH3 (n = 2, 3, 4). Measurements on $$rho$$ and $$nu$$ were carried out, respectively, using an Anton Paar DMA 602 vibrating-tube densimeter and an Ubbelohde viscosimeter. The $$rho$$ values were used to compute excess molar volumes, $$V_{{text{m}}}^{{text{E}}}$$, and, together with the $$nu$$ results, dynamic viscosities ($$eta$$). Deviations from linear dependence on mole fraction for viscosity, $$Delta eta$$, are also provided. Different semi-empirical equations have been employed to correlate viscosity data. Particularly, the equations used are the: Grunberg–Nissan, Hind, Frenkel, Katti–Chaudhri, McAllister and Heric. Calculations show that better results are obtained from the Hind equation. The $$V_{{text{m}}}^{{text{E}}}$$ values are large and negative and contrast with the positive excess molar enthalpies, $$H_{{text{m}}}^{{text{E}}}$$, available in the literature, for these systems. This indicates that structural effects are dominant. The $$Delta eta$$ results are positive and correlate well with the difference in volumes of the mixture compounds, confirming the importance of structural effects. The temperature dependences of $$eta$$ and of the molar volume have been used to calculate enthalpies, entropies and Gibbs energies, $$Delta G^{*}$$, of viscous flow. It is demonstrated that $$Delta G^{*}$$ is essentially determined by enthalpic effects. Methanol + CH3–O–(CH2CH2O)n–CH3 mixtures have been treated in the framework of the ERAS model. Results for $$H_{{text{m}}}^{{text{E}}}$$ are acceptable, while the composition dependence of the $$V_{{text{m}}}^{{text{E}}}$$ curves is poorly represented. This has been ascribed to the existence of strong dipolar and structural effects in the present solutions.