Rheological behavior pseudoplastic

Slurry Viscosity. Viscosities of magnesium hydroxide slurries are determined by the Brookfield Viscometer in which viscosity is measured using various combinations of spindles and spindle speeds, or other common methods of viscometry. Viscosity decreases with increasing rate of shear. Fluids, such as magnesium hydroxide slurry, that exhibit this type of rheological behavior are termed pseudoplastic. The viscosities obtained can be correlated with product or process parameters. Details of viscosity deterrnination for slurries are well covered in the Hterature (85,86). 

Rubber-based nanocomposites were also prepared from different nanofillers (other than nanoclays) like nanosilica etc. Bandyopadhyay et al. investigated the melt rheological behavior of ACM/silica and ENR/silica hybrid nanocomposites in a capillary rheometer [104]. TEOS was used as the precursor for silica. Both the rubbers were filled with 10, 30 and 50 wt% of tetraethoxysilane (TEOS). The shear viscosity showed marginal increment, even at higher nanosilica loading, for the rubber/silica nanocomposites. All the compositions displayed pseudoplastic behavior and obeyed the power law model within the experimental conditions. The... 

Dilatant Fluids. Dilatant fluids display a rheological behavior opposite to that of pseudoplastics (Figs. 2 and 3) in that the apparent... 

There are three types of non-Newtonian fluids plastic, pseudoplastic, and dila-tant. Figure 4.39 shows the rheological behaviors of Newtonian and non-Newtonian fluids. A plastic fluid does not move until the shear stress exceeds a certain minimum value, known as the yield value (f), and is expressed mathematically ... 

Dilutant liquids have rheological behavior essentially opposite those of pseudoplastics insofar as viscosity behavior is concerned. The r — y plots are concave upward and the power law applies... 

Power Law Fluid or Emulsion A fluid or emulsion whose rheological behavior is reasonably well-described by the power law equation. Here shear stress is set proportional to the shear rate raised to an exponent n, where n is the power law index. The fluid is pseudoplastic for n < 1, Newtonian for n = 1, and dilatant for n > 1. 

There are many pseudoplastic food products that display more complex rheological behavior and with a yield stress that can be characterized in two ways, either by an extension of the power law rheological equation of Herschel-Bulkley ... 

Fig. 1 Classes of rheological behavior that can be shown by coal slurries, as they appear when plotted on a shear rate/ shear stress graph. It is desirable for coal slurries to be Bingham plastic or pseudoplastic with yield, as such slurries flow readily at high shear rates (such as during pumping or atomization), while remaining stable against settling at low shear rates because of their yield stress. Dilatant slurries are completely unsuitable for coal slurry applications because they are extremely difficult to pump.

The rheological behavior of aqueous pAm solutions is typically pseudoplastic. An example of the use of pAm polymer to thicken an acidic composition is disclosed in patent application WO 9419443 A1 [16]. 

For the most part, PFDs exhibit shear-thinning (pseudoplastic) rheological behavior that is either time-independent or time-dependent (thixotropic). In addition, many PFDs also exhibit yield stresses. The time-independent flow curves are illustrated in Figure 1. The shear-thinning behavior appears to be the result of breakdown of relatively weak structures and it may have important relationship to mouthfeel of the dispersions. Because the viscosity of non-Newtonian foods is not constant but depends on the shear rate, one must deal with apparent viscosity defined as ... 

Block polymers, owing to the tendency for formation of regular strucmres tailored by molecular design, are ideal models for compatibilized, two-phase polymer blends or alloys. Blends do show similar rheological behavior, e.g., yield, pseudoplasticity, thixotropy, structural rearrangements, but since the morphology is more difficult to control, the interpretation of data could present serious difficulties. 

The concentration dependence of the Brookfield viscosity (Figures 9 and 10) indicates a rapid drop in viscosity upon dilution below a critical concentration. Bagley (7) attributed such rheological behavior to a structure of swollen, deformable gel particles closely packed in intimate contact. Davidson (8) later attributed the thickening efficiency of a cross-linked poly(acrylic acid) to the dispersed rather than the continuous phase. In general, pseudoplastic and viscoplastic rheology is characteristic of dispersions with low... 

PVC pastes exhibit complex rheological behavior with the viscosities showing dependence on the shear rate and on the time of shear. A paste viscosity may increase with shear rate (dilatancy) or decrease shear thinning or pseudoplasticity). Some pastes may show dilatant tendencies over one range of shear rates but... 

Pectins are insoluble in most organic solvents but, soluble in water up to 12% concentrations depending on the pectin type. The rheological behavior is close to Newtonian behavior at low concentrations but became pseudoplastic at higher concentration. ... 

The rheological behavior of sodium alginate solutions depends on the concentration and the shear rate. The Newtonian behavior and pseudoplastic behavior is observed at low shear rate and high sear rate, respectively. Higher concentrated solutions exhibit pseudoplastic flow even at low shear rates. 

The semisynthetic cellu1o.se derivatives, such as methyl-, ethyl-, or propyi-celIulo.se. can display various degrees of viscosity increase in the suspension their rheological behavior is typically pseudoplastic (see Chapter 16 in this vol-... 

Thus soluble polymer, interacting in a controlled fashion with colloidal particles, can transform both the equilibrium state and the mechanical properties of dispersions. The possibilities range from equilibrium, low viscosity fluids to nonequilibrium, pseudoplastic pastes with high yield stresses. However, substantial ga( still exist in the ability to, for example, (i) create high viscosity equilibrium fluids with prescribed relaxation spectra, (ii) impart a sol-gel transition at prescribed conditions, or (iii) connect explicitly macromdecular structure with rheological behavior. 

As previously observed, the xanthan C solution in sea water in the presence of proteins behaved like a thixotropic fluid. By contrast, an almost standard rheological behavior of a pseudoplastic fluid was found with the centrifuged solution in sea water with proteins added. A weak thixotropic effect was still observed probably because of the difficulty to completely eliminate cells from such a viscous fluid. 

Many water soluble polymers show a solution behavior which is non-Newtonian. When flow curves are experimentally obtained that plot the fluid shear stress versus shear rate, the curves show that in most cases the solution rheology is pseudoplastic. For pseudo-... 

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