Viscosity of concentrated polymer solutions

Tager and co-workers (51) have invoked bundle structures to explain correlations between the viscosities of concentrated polymer solutions and the thermodynamic interactions between polymer and solvent. They note, for example, that solutions of polystyrene in decalin (a poor solvent) have higher viscosities than in ethyl benzene (a good solvent) at the same concentration, and quote a number of other examples. Such results are attributed to the ability of good solvents to break up the bundle structure the bundles presumably persist in poor solvents and give rise to a higher viscosity. It seems possible that such behavior could also be explained, at least in part, by the effects of solvent on free volume (see Section 5). Berry and Fox have found, for example, that concentrated solution data on polyvinyl acetate in solvents erf quite different thermodynamic interaction could be reduced satisfactorily by free volume considerations alone (16). Differences due to solvent which remain after correction for free volume... 

Tager, A. A., Dreval.V.E. Non-newtonian viscosity of concentrated polymer solutions. Rheol. Acta 9,517-524 (1970). 

Simha,R., Utracki,L.A. The viscosity of concentrated polymer solutions corresponding states principles. Rheol. Acta 12,455-462 (1973). 

Onogi,S., Masuda,T., Miyanaga,N., Kimura,Y. Dependence of viscosity of concentrated polymer solutions upon molecular weight and concentration. J. Polymer Sci. Pt. A-2 5,899-913 (1967). 

Ferry,J.D, Grandine,L.D.,Jr., Udy.D.C. Viscosities of concentrated polymer solutions. III. Polystyrene and styrene-maleic acid copolymer. J. Colloid Sci. 8, 529-539 (1953). 

By postulating that the primary factor determining the concentration and temperature dependence of viscosities of concentrated polymer solutions is the mobility of each flow unit or a segment of polymer molecule in solution, Fujita and Kishimoto (1961) have derived an equation for the viscosity of such solutions. If we denote byBj, the value of B corresponding to the minimum hole required for one flow unit to allow of a considerable displacement, their equation can be put in the form ... 

For concentrated polymer solutions the viscosity is proportional to the 3.4th power of the molecular mass and about the 5th power of the concentration. The effects of temperature and concentration on viscoelastic properties are closely interrelated. The validity of a time-concentration superposition is shown. A method is given for predicting the viscosity of concentrated polymer solutions. 

Effect of molecular mass and concentration on the viscosity of concentrated polymer solutions... 

This section on concentrated suspensions discusses the rheological behavior of sj tems which are colloidally stable and colloidally unstable suspensions. For stable sj tems, the rheology of sterically stabilized and electrostatically stabilized systems wiU be considered. For sterically stabilized suspensions, a hard sphere (or hard particle) model has been successfid. Concentrated suspensions in some cases behave rheologically like concentrated polymer solutions. For this reason, a discussion of the viscosity of concentrated polymer solutions is discussed next before a discussion of concentrated ceramic suspensions. 

Hirai, N. The viscosities of concentrated polymer solutions. I. Moderately concentrated solutions. J. Polymer Sci. 39, 435 (1959). 

Onogi, D., T. Masuda, and N. Miyanaga Relationship between molecular weight and concentration determining the viscosity of concentrated polymer solutions. International Symposium on Macromolecular Chemistry Preprints, p. VIlI-223 (1966). 

Viscosity of concentrated polymer Solutions. II. Application of a free-volume treatment to polymer solutions. J. Appl. Polymer Sci. 10, 21 (1966). 

The average molecular weight, polydispersity, temperature, hydrostatic pressure, and shear rate dependences of polymer melt viscosity will be discussed in Chapter 13, resulting in a set of correlations which can be used to obtain a rough estimate of melt viscosity as a function of all of these variables. A new correlation will be presented for the molar viscosity-temperature function. The dependences of the zero-shear viscosity of concentrated polymer solutions on the average molecular weight and on the temperature will also be discussed. Finally, a new model that was developed to predict the shear viscosities of dispersions of particles in both polymeric fluids and ordinary molecular fluids will be presented. 

The zero-shear viscosity of a concentrated polymer solution can be treated by a modified version of the method used to calculate the zero-shear viscosity of a polymer melt. The modifications take the two effects of the solvent (plasticization and true dilution of the polymer) into account. Approximations are involved, however, in determining the appropriate mixing rules for the plasticization effect and the magnitude of the true dilution effect. The zero-shear viscosity of concentrated polymer solutions will be discussed briefly in Section 13.G. 

G. Zero-Shear Viscosity of Concentrated Polymer Solutions... 

A model for calculating viscosities of concentrated polymer solutions has been formulated and used successfully to predict viscosities of alkyd resin solutions in both pure aromatic solvents and in mixtures of hydrocarbons and oxygenated materials. It was also found to describe viscosity trends in polystyrene-diethylbenzene solutions accurately. The formulation explicitly accounts for the observation that concentrated solution viscosities increase markedly with decreasing compatibility between resin and diluent. The proposal of an empirical relationship which interprets the viscosity enhancement in poorer solvents in terms of increased chain-chain interactions is of interest. The model contains three constants which are fixed for a particular resin and are independent of diluent type. These are the Mark-HouuAnk constant, the parameter in the Martin viscosity equation, and the constant relating the postulated clustering to the solution thermodynamics of a particular solution. 

A new approach to calculating viscosities of concentrated polymer solutions has been presented. It consists of the derivation of a semi-empirical computational model containing three parameters characteristic of a particular polymer. Once these parameters have been established, the viscosity of any solution of the polymeric material in a solvent or solvent blend may be calculated. The method should be of particular interest to the coatings industry, where they often require a screening estimate of the potential viscosity-reducing power of a new solvent blend. 

Simha, R., and Chan, F. S., Corresponding state relations for the Newtonian viscosity of concentrated polymer solutions temperature dependence, J. Phys. Chem., 75, 256-267 (1971). 

Simha, R., Viscosity of concentrated polymer solutions. Journal ofMacromolecular Science -Physics, B5(2), pp. 425 28 (1971). 

Since the polymer solution remains quasi unehanged in eoneenlration, this modified VPO-method is faster than isopiestic isothermal distillation experiments with organic solvents and polymer solutions. Difficulties with the increasing viscosity of concentrated polymer solutions set limits to its applicability, because solutions should flow easily to form drops. 

Many different molecular weight grades of VP-based polymers, characterized by viscosity, are available commercially. The determination of viscosity is historically satisfactory for quality assurance purposes however, most physical properties of polymers are directly related to molecular weight. For example, the glass transition temperature and tensile strength of amorphous polymers are known to depend on molecular weight. The melt viscosity of polymers and the bulk viscosity of concentrated polymer solutions are also known to depend on molecular weight. 

Hoernschemeyer, D. (1974). Influence of solvent type on viscosity of concentrated polymer-solutions. Journal of Applied Polymer Science, 18( ), 61-75. 

Since ethanol is a precipitator for chitosan, its introduction into solutions of chitosan must degrade the thermodynamic quality of the solvent and increase the degree of stracturing and dynamic viscosity of concentrated polymer solutions. A monotonic decrease of the intrinsic viscosity and growth of Huggins constant in the studied range the ethanol ratio water (curves 1 and 2 in Figure 1, respectively) confirm the conclusion about the deterioration of the thermodynamic quality of mixture acetic acid-ethanol solvent. 

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