Pseudoplastic flow behavior

In most pseudoplastic liquids, Newtonian flow behavior is observed at sufficiently low and at high shear rates y, see Fig. 18. Viscosity approaching a constant value with low shear rates is called the zero-shear viscosity, p0 and its constant value at very high shear rates is called the infinite shear viscosity, p°°. 

In a dimensional-analytical discussion of the rheological constitutive equations, Pawlowski [36] furnished the proof that the rank of the dimensional matrix is always two. By a convenient association of the quantities contained in them, two dimensional material parameters can be produced (see Fig. 18)  

The relevance list of a process in which a rheological material participates is therefore extended by only two dimensional quantities. All the other material parameters can be transferred into dimensionless pi-numbers IIrheol. 

If the viscosity curve is plotted in a log-log scale and the transition range between p0 and po= is represented by a straight line with the slope m 1, see Fig. 18, then one speaks about a Ostwald-de Wade fluid whose viscosity curve obeys the so-called power laid (peff- effective viscosity, K - consistency index, m - flow index)  

Classical model fluids of this type are aqueous solutions of carboxy-methyl-cellulose (CMC), polyacrylamide (PAA), Carbopol (acidic polymers of acrylic acid of Goodrich), and so on. 

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Since HEC solutions have a pseudoplastic flow behavior, the apparent viscosity will change with the shear rates applied, and the intrinsic viscosity found experimentally will generally differ up to about 10% from the true intrinsic viscosity extrapolated to a shear rate of q = 0. The following empirical correction formula for this effect was proposed by Vink (48) ... 

The physical form of a drug product that is pourable displays Newtonian or pseudoplastic flow behavior and conforms to its container at room temperature. In contrast, a semisolid is not pourable and does not flow at low shear stress or conform to its container at room temperature [12], According to its physical characteristics, liquid dosage forms may be dispersed systems or solutions. 

A liquid is pourable it flows and conforms to its container at room temperature. It displays Newtonian or pseudoplastic flow behavior. 

In [26] the velocity fields and thereby the power for stirrers with simple geometry (anchor stirrer and gate stirrer) have been calculated for the laminar case (highly viscous liquid with Newtonian or pseudoplastic flow behavior) by the help of the numerical solution of the continuity and momentum balance in connection with the rheological constitutive equation. In the case of Newtonian fluids the power characteristic in the laminar flow range could be calculated for all three stirrers with the help of the expression ... 

The dynamic flow curves for the blend were significantly higher than what could be predicted from the component flow behavior. The blends showed regular, pseudoplastic flow behavior, without the yield stress. By contrast, capillary flow was found to be insensitive to temperature, suggesting a major modification of... 

The rheological properties were measured with a Couette viscosimeter (Haake) at shear rates from 7 to 1139 s . The pseudoplastic flow behavior follows the power law ... 

In a bubble column of 14 cm I.D. gas holdups, volumetric mass transfer coefficients and specific interfacial areas have been measured in CMC solutions of highly viscous pseudoplastic flow behavior. In the slug flow regime q, kLa and both a and kL follow simple relations (eqs. 8,10-12) which consider the influence of the gas velocity and the effective viscosity. The predictions of eq. (10) are in close agreement with the kLa values observed in a tower fermenter with fermentation broths of pronounced non-Newtonian flow behavior. 

These dependencies describe the pseudoplastic flow behavior without time-effects or the yield stress (ay). 

Rheology is the science of deformation and flow behavior of materials under the influence of parameters such as shear rate and time. Liquids with viscosity not dependent on shear rate are termed Newtonian liquids while non-Newtonian liquids exhibit changes in viscosity depending on shear rate. Most paints exhibit non-Newtonian flow, which is desirable. Important types of non-Newtonian flows are pseudoplastic flow behavior (shear thinning), thixotropic flow behavior (time-dependent shear thinning,) and dilatant flow behavior (shear thickening). Pseudoplastic or thixotropic flow is often desirable in coatings because ... 

When a shear stress is applied, the suspension structure is broken down into smaller units. The vehicle entrapped within the floe aggregates is released. This leads to a decrease in viscosity with increasing shear rate. If the rate of structure breakdown due to shear is equal to the rate of structure buildup due to brownian motion, shear thinning or pseudoplastic flow behavior is observed. The equilibrium floe is generally spherical in shape and the size distribution is narrow. ... 

Acrylic core-shell polymers have been used as principal pxjlymers for aqueous metallic basecoat paints [37—40]. The anionic shell allows pseudoplastic flow behavior which ensures parallel orientation of the aluminium pigments in the wet paint film. This orientation and the low solids content are responsible for the metallic gloss and high color flop (change in color observed on varying the viewing angle) of the basecoats. 

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