Shear viscosity measurements in the binary mixture butyl cellosolve-water near its upper and lower critical consolute points

Abstract

2014 Afin de tester l'universalité des concepts régissant les phénomènes critiques, la viscosité de cisaillement de mélanges binaires n-butylglycol (1)-eau a été étudiée au voisinage des deux températures critiques LCST et UCST respectivement d'origine entropique et enthalpique. Les valeurs des exposants critiques ~n de la viscosité de cisaillement sont obtenues par une analyse des résultats utilisant une renormalisation des coefficients de transport. Soient, pour le mélange UCST, ~ = 0,039 ± 0,001 (30,14 % en poids de n-butylglycol) et 0,036 ± 0,007 (24,78 %) tandis que pour le mélange LCST, ~ = 0,038 ± 0,001 (30,14 %) et 0,037 ± 0,003 (24,78 %). Ces exposants sont en bon accord avec le concept de couplage mode-mode et les prévisions du groupe de renormalisation. Abstract. 2014 To further probe the hypothesis of universality of critical phenomena, the shear viscosity has been measured for a two-component critical liquid system, butyl cellosolve-water, in the region of both the entropydriven lower (LCST) and the enthalpy-driven upper (UCST) critical solution temperature. The values of the critical exponents ~n for the shear viscosity were obtained by analysing the results from the viewpoint of multiplicative renormalization of transport coefficients. We have obtained ~n = 0.038 ± 0.001 (30.14 wt. %) and 0.036 ± 0.007 (24.78 wt. %) for the UCST mixture, and ~n, = 0.038 ± 0.001 (30.14 wt. %) and 0.037 ± 0.003 (24.78 wt. %) for the LCST mixture. These exponent values agree well with mode-mode coupling and renormalization-group predictions and satisfy the universality hypothesis.

Scaling of Shear Viscosity of Nitro‐benzene/Isooctane Mixtures in the Critical Region

“…This effect observed in experiments with other systems [2,3] is expected to be detected in a region near T e with D . r > 1 (D: shear rate; r: life time of local concentration fluctuations).…”

“…(5) is used to scale the viscosity data ofthe non-critical nitro-benzene/isooctane mixtures of different composition obtained at temperatures above the critical temperature T e . Equations of this type have been used before for the same purpose [2,3] (For the concept of scaling see e.g. [23]).…”

“…Therefore, with the information obtained for a limited number of systems, its application can be extended to other mixtures containing the same groups. The UNIFAC method has been employed by different authors to predict excess enthalpies; accordingly, Nagata and Ohta [2] utilized some temperature-dependent parameters in the method for analysing mixtures of alkanes with alkanols, ketones, esters and ethers.…”