Viscosity apparent/effective

It is particularly significant that no evidence is found for localized melting at particle interfaces in the inorganic materials studied. Apparently, effects commonly observed in dynamic compaction of low shock viscosity metals are not obtained in the less viscous materials of the present study. To successfully predict the occurrence of localized melting, it appears necessary to develop a more realistic physical model of energy localization in shock-compressed powders. 

Concentrations and types of sugars or oligosaccharides also affect the viscosity of pectin solutions. Chen and Joslyn (1967) and Kar and Arslan (1999a) found that sucrose, dextrose and maltose increased the viscosity of aqueous pectin solutions whereas dextrins reduced it. The viscosity-enhancing effect of the sugars was interpreted in terms of the decrease in dielectric constant of the solvent, dehydration action and hydrogen bonding formation. However, the effect of dextrins on the viscosity of pectin was apparently an artifact due to ionic impurities in the dextrin. 

This chapter is an in-depth review on rheology of suspensions. The area covered includes steady shear viscosity, apparent yield stress, viscoelastic behavior, and compression yield stress. The suspensions have been classified by groups hard sphere, soft sphere, monodis-perse, poly disperse, flocculated, and stable systems. The particle shape effects are also discussed. The steady shear rheological behaviors discussed include low- and high-shear limit viscosity, shear thinning, shear thickening, and discontinuity. The steady shear rheology of ternary systems (i.e., oil-water-solid) is also discussed. 

Leakage flow varies with the flight clearance. It is also enhanced by low-viscosity melts and high head pressures. With new screws and barrels, leakage flow is minor and has no apparent effect on extruder output. As the flight clearance increases, leakage flow rises, thereby reducing output. Consequently, the decrease in extruder output over time is used to monitor screw and barrel wear. 

PART III XANTHAN GUM, 637 Effect of Polymer Concentration on Apparent Viscosity, 637 Effect of Polymer Concentration on Screen Factor, 638 Effect of Sodium Chloride on the Apparent Viscosity of Biopolymers, 639 Effect of Cation Type on Polymer Viscosity, 642 Effect of Alkali Type on Polymer Viscosity, 643 Effect of Surfactants on Polymer Viscosity, 648 Combined Effect of Surfactants and Alkalis on Polymer Viscosity, 648... 

Carrier liquid absolute viscosity Apparent viscosity of a pseudoplastic fluid Effective viscosity... 

Shearer and Akers [5], Callaghan et al. [114] supposed that the mechanism involves elimination of surface tension gradients (see Section 4.4.3) as indicated by elimination of surface elasticity. These authors studied the effect of PDMSs on the surface elasticity of crude oil. PDMSs are used as antifoams to assist gas-oil separation during crude oil production and are apparently effective at the remarkably low concentration of 1 part per million (which presumably still exceeds the solubility limit). Callaghan et al. [114] find that PDMS diminishes the frequency-dependent dynamic dilational (elastic) modulus e = doAo (0/d In A(t) relative to that found for the uncontaminated oil. Here Oao(0 is the time-dependent air-crude oil surface tension, and A(t) is the area of a constrained element of air-crude oil surface subject to time-dependent dilation. The effect is more marked the higher the molecular weight (or viscosity) of the PDMS. This correlates with an enhanced antifoam effectiveness found with increase in molecular weight. 

The units of measurements of apparent viscosity or effective viscosity are the same as those used for viscosity when we refer to a Newtonian fluid. We have mainly used Ib/ft s, which is the unit of viscosity in the fps system. 

By the way, this also provides us with another expression for apparent viscosity or effective viscosity, as follows ... 

When an electrolyte, such as NaCl, is added to a polymer solution, the repulsive forces are screened by a double layer of electrolytes and extension is reduced. As the electrolyte concentration increases, the extension of the polymer chain decreases and the solution viscosity declines. Fig. 5.1533 illustrates the effect of salinity on the relative viscosity (apparent solution viscosity/solvent viscosity) of 250-ppm solutions of Pusher 700 , a partially hydrolyzed polyacrylamide.34 Chain extension also is controll by the... 

We are now in possession of the following information (1) the previously detected complex between and PEO in CD3OD has a pronounced effect on (2) a looser polymer-salt interaction, such as that responsible for salting out , in K2SO4-PEO-D2O solutions, has no apparent effect on (3) the salting-out interaction has a pronounced effect on solution viscosity. Complex formation may also affect polymer viscosity but it is difficult to separate its influence from the salting-out process. 

Among the complications that can interfere with this conclusion is the possibility that the polymer becomes insoluble beyond a critical molecular weight or that the low molecular weight by-product molecules accumulate as the viscosity of the mixture increases and thereby shift some equilibrium to favor reactants. Note that we do not express reservations about the effect of increasing viscosity on the mobility of the polymer molecules themselves. Apparently it is not the migration of the center of mass of the molecule as a whole that determines the reactivity but, rather, the mobility of the chain ends which carry the reactive groups. 

Sihcate solutions of equivalent composition may exhibit different physical properties and chemical reactivities because of differences in the distributions of polymer sihcate species. This effect is keenly observed in commercial alkah sihcate solutions with compositions that he in the metastable region near the solubihty limit of amorphous sihca. Experimental studies have shown that the precipitation boundaries of sodium sihcate solutions expand as a function of time, depending on the concentration of metal salts (29,58). Apparently, the high viscosity of concentrated alkah sihcate solutions contributes to the slow approach to equihbrium. 

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