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Zhidk. krist. ikh prakt. ispol'z. = Liq. Cryst. and their Appl., 2017, 17 (3), 70—82. DOI: 10.18083/LCAppl.2017.3.70
Non-Newtonian Flow of Structured Systems. XXIII. Viscoelastic Properties of Polymer Solutions
E. A. Kirsanov, Yu. N. Timoshin
Author affiliations State University of Humanities and Social Studies,
30 Zelyonaya St., Kolomna, 140411, Moscow Region, Russia
Abstract Polymer solutions are considered as structured fluids. The structural rheological model is used to describe rheological properties of the following polymer solutions: aqueous solutions of xanthan gum, polyacrylamide, carboxymethylcellulose, sodium carboxymethylcellulose, polyacrylic acid in ethylene glycol, an aqueous solution of polyacrylamide before and after prolonged intensive shear. The sections of rheological curves , corresponding to different states of the structure of the investigated samples, are determined. Approximation of these rheological curves is carried out using the rheological equations of the structural model. The structural model equations, obtained for the description of shear viscosity, loss modulus and storage modulus, approximate well the experimental data up to three orders of magnitude of the shear rate or cyclic frequency. At the range of the low shear rates or cyclic frequency, the linear dependence of the root values of shear stress, loss modulus and storage modulus observed sometimes. Intervals of the low shear rates (or cyclic oscillation frequencies) correspond to the "Newtonian" flow state, where the state of the structure practically does not change. As the shear rate (or the cyclic frequency) increases further, the structure gradually begins to degrade (a decrease in the number of macromolecules engagements). In some samples of polymer solutions, the calculated limiting viscosity values (at an infinite shear rate and infinite cyclic frequency) have practically the same value, which is the evidence of the similar nature of the structure destruction under steady flow and with shear oscillations.