04/2002; DOI: 10.1021/ja02254a001
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    ABSTRACT: In this work, a model for calculating the dynamic viscosity of polymer solutions was developed. The model is based on the Eyring absolute rate theory and on the solution theory of McMillan−Mayer. An equation of state is used for the calculation of the solution osmotic pressure and, thus, the excess molar McMillan−Mayer free energy. The final expression shows an explicit dependence between the viscosity of the polymer solution and the applied shear stress. The proposed model contains three terms. The first term describes the viscosity of an ideal polymer solution. The second term takes into account non-Newtonian behavior of the polymer solution. Finally, the third term represents the deviation from the thermodynamic ideal behavior. The whole model presented five adjustable parameters, with two of them also considered as being a function of the applied shear stress. To test the proposed model, we have measured experimental rheological data for poly(ethylene glycol) aqueous solutions (nominal molecular weight 6000 g/mol) for nine different polymer concentrations, at different shear rates, at 313.15 K and 0.1 MPa. The proposed model has been used for correlating the experimental viscosity data of these polymer solutions at different values of the applied shear stress and polymer concentration. It has been found that the agreement between the experimental and calculated values is within the experimental error.
    Industrial & Engineering Chemistry Research - IND ENG CHEM RES. 12/2005; 45(2).
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    ABSTRACT: The influence of water on cellulose dissolved in 1-ethyl-3-methylimidazolium acetate (EMIMAc) is analysed by measuring steady state viscosity of dilute solutions. The goal is to determine: (a) the maximal water content allowing keeping cellulose dissolved (in dilute regime) and (b) the influence of water on solution flow and cellulose hydrodynamic properties. Mixing EMIMAc and water is exothermal and EMIMAc-water viscosity does not obey a logarithmic mixing rule suggesting strong interactions between the components. Newtonian flow of cellulose-EMIMAc-water solutions was recorded at water concentrations below 15 wt% and a shear thinning was observed for higher water content. It was suggested that above 15 wt% water cellulose is not completely dissolved: swollen aggregates form a sort of a “suspension” which is structuring under shear. Cellulose intrinsic viscosity showed a peak at 10 wt% water-90 wt% EMIMAc. It was hypothesised that the addition of water leads to the formation of large cellulose aggregates due to the preferential cellulose–cellulose interactions.
    Cellulose 19(1). · 3.48 Impact Factor
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    ABSTRACT: The generalized hole theory has been developed for the estimation of viscosity of liquid mixtures and has been applied for the calculation of viscosity of four binary [viz. toluene + cyclohexane (I), toluene + carbon tetrachloride (II), cyclohexane + carbon tetrachloride (III) and benzene + n-hexane (IV)], four ternary [viz. carbon tetrachloride + cyclohexane + benzene (I), toluene + n-heptane + n-hexane (II), cyclohexane + n-heptane + n-hexane (III) and n-hexane + n-heptane + n-decane (IV)] and one quaternary liquid mixture [viz. carbon tetrachloride + cyclohexane + benzene + toluene]. The calculated values obtained are compared with the experimental values of viscosities.
    Proceedings of the National Academy of Sciences, India - Section A 83(3). · 0.17 Impact Factor