Viscosity temperature dependence, aqueous solution

Monkos, Karol 1997. Concentration and temperature dependence of viscosity in lysozyme aqueous solutions. Biochimica et Biophysica Acta 1339, 304-310. 

Figure 5.7 shows the temperature dependence of the viscosity of water-methanol and water-acetonitrile mixtures in the entire composition range [132]. The existence of a viscosity maximum for a methanol concentration close to 45% is conspicuous. For water-acetonitrile, there is also a viscosity maximtun, but it is less pronounced and takes place at a lower organic solvent concentration ( 20%). We also show in Figure 5.8 the variation of the viscosity of various aqueous solutions with their composition [135]. 

Figure 14 shows the temperature dependence of the viscosity of an aqueous solution of PMAA (curve 1) and equimolar PMAA-PEG mixtures containing equal concentrations of the repeating units of the two components (curves 2 and 3) A pronounced... 

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 presence of cross-linked phosphates may be recognized by their ready hydrolysis, which leads to a rapid drop in the viscosity of the solution and a parallel decrease in its pH. Aqueous solutions of all cross-linked phosphates are hydrolyzed after twenty hours. In contrast to the hydrolysis of normal P—O—P bonds in meta- and polyphosphates, that of the cross-linking sites is practically independent of concentration, pH, ionic strength and the nature and concentration of added salts. It does, however, follow a first-order law, as for normal P—O—P bonds, and is strongly temperature dependent. Activation energies of 18.9 and 15.4 kcal/mole have been... 

Sodium alginate35 This material is insoluble in aqueous solutions in which pH is less than 3. It dissolves slowly in water, forming a viscous colloidal solution. Various grades yield various viscosities (1% w/v aqueous solution has a viscosity of 20 to 400 mPa-s at 20°C). Viscosity may vary depending on concentration, pH, and temperature. 

The conversion of dextran with 1,2-epoxy-3-phenoxypropane, epoxyoctane or epoxydodecane may be exploited for the preparation of amphiphilic dextran derivatives. Polymeric surfactants prepared by hydrophobic modification of polysaccharides have been widely studied, starting with the pioneering work of Landoll [261]. Neutral water-soluble polymeric surfactants can be obtained by reaction of dextran with 1,2-epoxy-3-phenoxypropane in 1 M aqueous NaOH at ambient temperature (Fig. 35, [229,233]). The number n of hydrophobic groups per 100 Glcp units varies between 7 and 22 depending on the reaction conditions. 2-Hydroxy-3-phenoxy propyl dextran ethers (DexP) behave like classical associative polymers in aqueous solution. In dilute solution, the intrinsic viscosity decreases significantly whereas... 

The type of polymer obtained depends on factors such as the pH and temperature of reaction, the ratio of melamine to formaldehyde, and the type of catalyst employed. For decorative laminates, melamine-formaldehyde is prepared by reacting melamine in stainless steel kettles under reflux, alkaline conditions with 37% to 46% formaldehyde in aqueous solution. The reaction temperatures used vary from 80 to 100°C and are maintained until the condensation has reached the desired end point—that is, reacted sufficiently but still water-soluble. The end point is checked by measurements of viscosity, cure time, and water tolerance. Depending on the type of laminate to be produced, other constituents (surfactants, plasticizers, release and anti-foam agents) normally are added to the base resin before impregnation of the surface papers. It is common practice also at this stage to adjust the pH by adding acid catalysts. 

Fig. 11 Standard representation of the temperature dependence of viscosity of aqueous sugar solutions of different concentrations as well as their reference-invariant approximation using ip = -0.500 (solid curve). For key parameters a(x)...

Fig. 11 shows the reference-invariant representation of the temperature dependence of viscosity of aqueous sugar solutions of different concentration (x - mass portion of cane sugar). To obtain this correlation, p and (T - T0) had to be transformed by the transformation or key parameters a = 1/yo [K] and b [Pa s] as w = p/b and u = (T-T0)/a, whereby a and b are functions ofx, see auxiliary diagram in Fig. 11. The reference temperature is T0 = 20 °C.

The dilution of solutions33 containing equimolar ratios of monomer units of the complex components results in the dissociation of the complexes of PMAA with low-molecular weight PEG. The reduced viscosity of solutions rapidly increases, which indicates the existence of the equilibrium PMAA + PEG complex. In the case of a relatively high-molecular weight PEG, the PMAA macromolecules are firmly connected with PEG and at the dilution of aqueous solution, an increase of the reduced viscosity typical of polyelectrolytes does not occur, i.e. the complex does not dissociate. The absence of temperature dependence of the relative viscosity in the temperature range 15-40 °C is indicative of the stability of this complex (Fig. 4). 

The technological importance of xanthan gum rests principally on its unusual and distinctive properties25 28 29 49,116,251,257-260 in aqueous solution. Some of these properties are (1) remarkable emulsion-stabilizing and particle-suspension ability, (2) low concentrations yield high viscosities, (3) recoverable shear-thinning (extremely large shear dependence of viscosity), (4) little variation in viscosity with temperature under normal conditions of industrial utilization, and (5) gel formation when mixed with certain other, nongelling polysaccharides. 

The temperature dependences of electrolytic conductivity of several EMI salts are given in Figure 17.4 and compared with those of an aqueous solution (4.5 M H2SO4/H2O) and a nonaqueous propylene carbonate solution (1 M EtsMeNBFV PC) [36-38]. Note that most ionic liquids (Figure 17.4a) show inferior conductivity compared to their aqueous and nonaqueous counterparts (Figure 17.4h) at low temperatures. This is because of their higher viscosities, and their conductivities at —20°C are less than 1 mS cm EMIF 2.3HF is the only one exception. It shows... 

Figure 3.49 shows results of measurements [72a] of the temperature dependence of viscosity for water and aqueous solutions of DMSO (dimethylsulfox-ide). These tests were made in preparation for measuring the viscosity of a rare and expensive glycoprotein. In this case, measuring viscosity acoustically is a distinct advantage, as fewer than six microliters of sample are required. 

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