Aqueous solutions viscosity

ALCOGUM 296-W is a high viscosity aqueous solution of sodium polyacrylate. It is an anionic colloid furnished as a whitish colored homogeneous solution at 15% solids, ready for use. 

Viscose, Aqueous solution of cellulose xanthogenate. In the coagulating bath, viscose again becomes cellulose as a filament, film, or sponge. Viscose filament is one of the man-made fibres, viscose film is a packaging material, viscose sponge is a household article. 

The linear chain polymer forms extremely high-viscosity aqueous solution. Forms a gel that is elastic and thermally nonreversible under existence of alkali. The gel strength multiplies with the simultaneous use of xanthan gum and carrageenan. The interaction between arum root mannan and xanthan is stronger than the interaction between xanthan and galactomannan. 

Protein molecules extracted from Escherichia coli ribosomes were examined by viscosity, sedimentation, and diffusion experiments for characterization with respect to molecular weight, hydration, and ellipticity. These dataf are examined in this and the following problem. Use Fig. 9.4a to estimate the axial ratio of the molecules, assuming a solvation of 0.26 g water (g protein)"V At 20°C, [r ] = 27.7 cm g" and P2 = 1.36 for aqueous solutions of this polymer. 

In packed beds of particles possessing small pores, dilute aqueous solutions of hydroly2ed polyacrylamide will sometimes exhibit dilatant behavior iastead of the usual shear thinning behavior seen ia simple shear or Couette flow. In elongational flow, such as flow through porous sandstone, flow resistance can iacrease with flow rate due to iacreases ia elongational viscosity and normal stress differences. The iacrease ia normal stress differences with shear rate is typical of isotropic polymer solutions. Normal stress differences of anisotropic polymers, such as xanthan ia water, are shear rate iadependent (25,26). 

Uses of gelatin are based on its combination of properties reversible gel-to-sol transition of aqueous solution viscosity of warm aqueous solutions abUity to act as a protective coUoid water permeabUity and insolubUity in cold water, but complete solubUity in hot water. It is also nutritious. These properties are utilized in the food, pharmaceutical, and photographic industries. In addition, gelatin forms strong, uniform, clear, moderately flexible coatings which readily sweU and absorb water and are ideal for the manufacture of photographic films and pharmaceutical capsules. 

A significant heat-transfer enhancement can be obtained when a nonckcular tube is used together with a non-Newtonian fluid. This heat-transfer enhancement is attributed to both the secondary flow at the corner of the nonckcular tube (23,24) and to the temperature-dependent non-Newtonian viscosity (25). Using an aqueous solution of polyacrjiamide the laminar heat transfer can be increased by about 300% in a rectangular duct over the value of water (23). 

Concentration and Molecular Weight Effects. The viscosity of aqueous solutions of poly(ethylene oxide) depends on the concentration of the polymer solute, the molecular weight, the solution temperature, concentration of dissolved inorganic salts, and the shear rate. Viscosity increases with concentration and this dependence becomes more pronounced with increasing molecular weight. This combined effect is shown in Figure 3, in which solution viscosity is presented as a function of concentration for various molecular weight polymers. 

The viscosity of the aqueous solution is also significantly affected by temperature. In polymers of molecular weights (1-50) x 10 , the solution viscosity may decrease by one order of magnitude as the temperature of measurement is increased from 10 to 90°C. Figure 5 shows this effect. 

Effect of Shear. Concentrated aqueous solutions of poly(ethylene oxide) are pseudoplastic. The degree of pseudoplasticity increases as the molecular weight increases. Therefore, the viscosity of a given aqueous solution is a function of the shear rate used for the measurement. This relationship between viscosity and shear rate for solutions of various molecular weight poly(ethylene oxide) resins is presented in Figure 8. 

Fig. 8. Effect of shear on aqueous solution viscosities of poly (ethylene oxide) resins (a) 1.0 wt % solution, (b) 5.0 wt % solution (10). Each curve...

Aqueous solutions can be stabilized against viscosity loss by addition of 5—10 wt % anhydrous isopropyl alcohol, ethanol, ethylene glycol, or propylene glycol. The manganous ion (Mn " ) also is an effective stabilizer at concentrations of 10 -10 wt% of the solution. 

Of the three worldwide manufacturers of poly(ethylene oxide) resins. Union Carbide Corp. offers the broadest range of products. The primary quaUty control measure for these resins is the concentrated aqueous solution viscosity, which is related to molecular weight. Specifications for Polyox are summarized in Table 4. Additional product specifications frequendy include moisture content, particle size distribution, and residual catalyst by-product level. 

Table 4. Aqueous Solution Viscosity Specifications for Polyox Resins ...

Aqueous Solution Viscosity. A special solution preparation method is used for one type of measurement of aqueous solution viscosity (96). The appropriate amount of poly(ethylene oxide) resin is dispersed in 125 mL of anhydrous isopropyl alcohol by vigorous stirring. Because the resin is insoluble in anhydrous isopropyl alcohol, a slurry forms and the alcohol wets the resin particles. An appropriate amount of water is added and stirring is slowed to about 100 rpm to avoid shear degradation of the polymer. In Table 4, the nominal resin concentration reported is based on the amount of water present and ignores the isopropyl alcohol. 

Physical and chemical properties of the numerous PAG products can vary considerably. PAG products are usually aqueous solutions, although soHd products are also sold. Solutions range from colodess to amber and from clear to hazy in appearance specific gravities at 25 °G vary from about 1.2 to 1.35. Product viscosities, as measured by a Brookfield viscometer at 25 °G, are generally about 10 50 mPa-s(=cP), but can be much greater than 10, 000 mPa-s(=cP) for certain aged compositions. 

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