The viscosity and structure of dispersed systems

Matveenko, V. N.; Kirsanov, E. A.

doi:10.3103/s0027131411040079

Cited by 35 publications

(26 citation statements)

References 71 publications

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“…, where η τ -is the effective viscosity at given shear stress; η мах -is a maximal viscosity corresponding to nonvolatile initial structure; -η ∞ is the less viscosity, corresponding to breaking point [67]. When EDSD < 1 the recovery processes prevail destruction processes and vice-versa when EDSD > 1.…”

Section: Methodsmentioning

confidence: 99%

Rheology of plasticized polymer solutions

Umerova¹,

Dulina²,

Ragulya³

2015

Epitoanyag - JSBCM

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this paper is about rheological properties of plasticized polymer solutions with different concentration of plasticizer. it was established that the investigated polymer solutions were threedimensionally structured systems which were shear thickened at low shear rates and maintained the thixotropic structural state under high shear rates. However, addition of different amount of plasticizer had an ambiguous influence on rheology of solutions and led to formation of transient polymer network with a complicated character of structuration because of the features of interaction in the polymer -plasticizer system. it was found that the plasticization results in changing of ec molecules conformation and simultaneous breaking of the polymer continuity due to DBP adsorption on ec macromolecule. Herewith, the formation of smaller crystallites took place. Besides, the investigated solutions showed causal link between structural states.

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Section: Methodsmentioning

confidence: 99%

Rheology of plasticized polymer solutions

Umerova¹,

Dulina²,

Ragulya³

2015

Epitoanyag - JSBCM

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“…The model′s empirical constants φ max,1 and φ max,2 are found from the dependences 1 r 1 r max,1 max,1 r r , . 1 1…”

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“…The accuracy of approximation of experimental data can be improved by two methods: by increasing the number of empirical constants in the model′s computational equations and by subdividing viscosity curves into individual portions which are described by different equations with their own empirical constants [1]. We will use the second variant and the existing phenomenological models.…”

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confidence: 99%

Selection and Verification of Phenomenological Suspension-Viscosity Models

Федотов

2015

J Eng Phys Thermophy

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An analysis of the accuracy of the existing phenomenological suspension-viscosity models has been made. A procedure for approximating the viscosity curve by three one-parametric models but identifying only two empirical parameters has been proposed. Phenomenological models most accurately describing experimental data for suspensions of different compositions in the entire range of concentrations of a dispersed phase have been established.Introduction. Numerous empirical and semiempirical equations have been proposed for quantitative description of the viscosity of suspensions in the entire range of concentrations of a dispersed phase. With nearly identical degree of accuracy, one can describe, with one and the same equation, systems different in physicochemical nature, and with different rheological equations, one and the same disperse system [1]. Therefore, a rheological equation for approximation of experimental data is selected subjectively from the researcher′s own experience. Equations with the smallest number of empirical constants are preferred. An analysis of the literature shows that, for suspensions, one generally uses equations with one phenomenological parameter: the critical concentration of inclusions of the dispersed phase φ max , at which the viscosity becomes infi nite. The adequacy of a phenomenological model is directly determined by quantitative assessment of the model′s parameters, which are identifi ed from experimental results. Formally, a one-parametric model can be verifi ed by one experimental point. However, the viscosities of diluted and highly fi lled suspensions differ by an order of magnitude or more. Therefore, one uses several experimental points to approximate the viscosity curve more accurately. Selection of the values and number of points, as the selection of the approximating equation, is subjective and has no substantiation.The aim of the present work is to work out recommendations as far as the selection and improvement of accuracy of phenomenological models are concerned.Procedure of Verifi cation of Phenomenological Models. The rheological properties of a suspension are characterized by the relative viscosity defi ned as the ratio of the viscosity of a suspension to the viscosity of a liquid dispersion phase. The literature gives different dependences of the relative viscosity of suspensions η r on the volume concentration of a dispersed phase φ. We will consider one-parametric equations describing this difference with one empirical constant φ max (Table 1).Experimental dependences of the relative viscosity of different suspensions on the volume fraction of a dispersed phase are presented in Fig. 1. It is seen that the corresponding curves differ considerably. Therefore, for each composition of the suspension, we should determine its own empirical constant φ max . First we consider suspensions with a low (curve 1) and a high (curve 6) viscosity. We will approximate experimental data by equations of models 3, 6, and 9 (Table 1) which are the most accurate. The empirical con...

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“…However, the difference of their MW should be kept in mind. The structural coefficients that were determined from functions τ = f(γ) using an exponential mathematical approximation [9] for SH and SA solutions (2%) were 36.76 and 4.52, respectively. The structural coefficient of mixed solutions increased smoothly with increasing SH fraction.…”

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Rheological and Film-Forming Properties of Mixed Sodium Alginate and Hyaluronate Solutions

Yusova

Lipatova

2014

Fibre Chem

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The rheological properties of mixed solutions of the biologically active polysaccharides sodium alginate and hyaluronate in addition to the microstructure and physicomechanical properties of films formed from them were studied. It was found that the particle size of a discrete phase in microheterogeneous alginate-hyaluronate films was determined by the drying time of the starting aqueous mixtures. Synergy was found with respect to the film tensile strength if the polysaccharides were mixed.Materials made of natural polymers, in contrast with synthetic polymers, are non-toxic and biocompatible. Aqueous systems (solutions and hydrogels) based on biologically active polysaccharides are especially interesting. Such polysaccharides have broad applications in pharmacology, cosmetology, biotechnology, and bioengineering [1]. New materials with properties of each component can be prepared by using aqueous polysaccharide mixtures.We studied the biologically active natural polymers sodium alginate, an anionic polysaccharide and product from processing brown algae, and sodium hyaluronate, a mucopolysaccharide and component of mammal connective tissue. Both polymers have high water-retention capacity, wound-healing and hemostatic effects, and other valuable properties that enable them to be used in cosmetology and medicine as hydrogel matrices for time-release drugs [2]. The sorption and transport properties of composite matrices depend on their structure, which is determined largely by the compatibility of the polymer components [3,4]. The rheological behavior of polymer compositions and the microstructure of films formed from them provide information about the compatibility of the polymers in a common solvent.The goal of the present work was to evaluate the compatibility of sodium alginate (SA) and hyaluronate (SH) from results of rheological tests and film-forming properties of mixed solutions of these polymers.We studied industrial samples of SA of molecular weight (MW) 2 20 kDa and SH of MW 987 kDa. The inherent viscosity [η] was calculated from the concentration dependence of the reduced viscosity. The measurements were made in an Ubbelohde viscometer at 25°C. The solvent for SA was NaCl solution (0.1 M). The weight-average MW of SA was calculated using the equation [5] [η] = 0.023 . M 0.984 ,where M is the SA molecular weight. The solvent for SH was NaCl solution (0.2 M). The weight-average MW of SH was calculated using the equation [6] [η] = 2.28 . M 0.816 .(2)

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The viscosity and structure of dispersed systems

Cited by 35 publications

References 71 publications

Rheology of plasticized polymer solutions

Rheology of plasticized polymer solutions

Selection and Verification of Phenomenological Suspension-Viscosity Models

Rheological and Film-Forming Properties of Mixed Sodium Alginate and Hyaluronate Solutions

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