Thinning effect

The curve for core size distribution—Foster s plot of 6 j6r against r —is also shown, as Curve D, in Fig. 3.18. It differs markedly from the pore size distribution curves, clearly showing that the corrections for the film thinning effect which have become possible since Foster s day, are of first-order importance. 

In the manufacture of paper, starch-based adhesives are used either to strengthen the paper base or for coating the surface of the paper. Raw starch is unsuitable for either purpose. To achieve sufficient adhesive power with raw starch would require the application of a solution that was far too thick for practical use. Instead, chemically modified starch, with a much lower viscosity in solution, is used. As an economical alternative to modifying the starch with aggressive oxidizing agents, the starch can be treated with enzymes ( df-amylases) to obtain the same thinning effect... 

We can solve for Q by trial and error after setting the limit in eqn. (6.199) to i. Figure 6.40 presents the value for Q as a function of power law index. As can be seen, the shear thinning effect is not very large. 

In addition to the shear thinning effect, other non-Newtonian properties bring about additional complexities in the flow pattern, as demonstrated by Unkriier (37), such as cross-machine flow superimposed on the main machine-direction flow in the inlet region. 

The physical meaning of this result is that the drag removal action of the barrel is reduced by a factor of 0.814 as a result of the temperature profile in the film on which the shear thinning effect is superimposed. 

A. J. Poslinski and D. J. Coyle, Steady Gas Penetration through Non-Newtonian Liquids in Tube and Slit Geometries Isothermal Shear-Thinning Effects, Proc. Polymer Processing Society, 10th Annu. Meet., Akron, Ohio (1994), pp. 219-220. 

Thixotropy provides a shear thinning effect that is, viscosity decreases as the shear rate increases, and vice versa. This not only allows easy pumping, dispensing, and mixing of the adhesive, but also provides sag resistance once the adhesive is applied. The thixotropic fillers work by forming a temporary structure in the mixture, which can be broken down at high rates of shear. This structure is generally the result of van der Waals forces between molecules. 

LIME SULPHUR SOLUTION. Lime sulphur solution is one of the most important fungicides in organic fruit growing. A thinning effect was observed in some trials. Use of 20-40 kg/ha (2,0-4.0%) at full bloom is recommended. Cultivar sensitivity and possible side effects on beneficial fauna should be determined by careful experimentation. 

Slight infestation in strong-flowering varieties has a desirable thinning effect. 

Areas of application Mode of action Remarks Aphids, pear suckers Direct insecticidal action is only moderate, dissolves honeydew Russeting can occur under dry weather conditions Spraying at apple blossom time has a thinning effect... 

As the cell walls are squeezed into polyhedra, a wall-thinning effect takes place, and liquid is drained from cell-wall faces into the lines of cell intersections to form ribs or struts, which are typically triangular in cross-section. This cell wall membrane thinning can continue to the point where the cell walls collapse and the cells open. This becomes a very important characteristic of most plastic foams, and affects properties such as thermal conductivity, moisture absorption, breathability, and load bearing. 

Poslinski, A. J., Ryan, M. E., Gupta, R. K., Seshadri, S. G., and Frechette, F. J. 1988. Rheological behavior of filled polymeric systems I. Yield stress and shear-thinning effects, y. Rheol. 32 703-735. 

The behavior of lyotropic crystals is usually non-Newtonian. Lamellar liquid crystals show thixotropic or negative thixotropic behavior,but shear thinning/thixotropy is more common. The shear thinning effect is ascribed to orientation of the liquid crystalline domains and some structural breakdown. Viscoelasticity has also been observed. If the concentration of the surfactant molecules is, however, low and close to the CMC, Newtonian flow will be observed. ... 

With increasing shear, Pe — the relative viscosity of suspensions — usually decreases (see Fig. 6.19). This shear thinning effect is quite moderate in colloidally stable suspensions, which actually can behave as nearly Newtonian up to... 

It is seen that the MC acts as a thickener over the whole region studied. The shear thinning effect of the polymer in the shear rate region 0.1/s to 100/s is however not sufficient for the film-coating purpose mentioned. The coating layer thickness of course increases with increasing MC content. 

LLDPE similar to LLDPE-A polymer, the LPX-30. For PP a strain thinning effect may be suspected. In Fig. 22 the steady state viscosities for PP and BL ngCe) 3n(oi) were reported. For the other samples... 

This shear reversibihty is very beneficial in enhanced oil recovery field applications. It improves the well injectivity because of the shear thinning effect at the perforation and near the wellbore. Far away from the wellbore, flow velocity is reduced and viscosity is restored. For the hydrophobically associating polymers, both shear thickening and shear thinning were observed by Bock et al. (1988). It has also been reported that the viscosity after shearing was stopped was higher than that before shearing (McCormick et al., 1988). 

U.S. 6515007 (2003) Murad Acidic component of a hydroxy acid or tannic acid or salts in combination with vitamin E component and an antigrowth agent for the antidandruff effect, or with niacin component and a 5-a reductase inhibitor for the antihair-thinning effect Antidandruff antihair thinning (three-in-one)... 

The effect of fluid rheology on the power consumption of helical ribbon agitators has also been evaluated [54] and power consumption as a function of generalized Reynolds number for shear thinning but inelastic fluids defined. When shear thinning effects are small, and elasticity is negligible, deviations from the Newtonian... 

The quotient (r /r o), which indicates the magnitude of shear thinning effect with increasing y, can be estimated quite well as a function of the Weissenberg number (Nwg) and the polydispersity [7], N yg is the product of a characteristic time scale for the polymer with y, and can be approximated by Equation 13.27 where p is the polymer bulk density at the temperature of calculation. (The density must be expressed in g/m3 rather than g/cc in Equation 13.27 for consistency with the units used for the other quantities entering this equation.) Since the polydispersity Mw/Mn enters Equation 13.27, r depends on the polydispersity both indirectly via the dependence of Ny/g on Mw/Mn and directly. 

Several types of dispersions show strain rate thinning, and a quantitative explanation is not easily given. We will briefly consider two cases. The first one concerns shear flow. As discussed (above, Factor 4), anisometric particles show rotational diffusion and thereby increase viscosity. This effect will be smaller for a higher shear rate when the shear-induced rotation is much faster than the diffusional rotation, the latter will have no effect anymore. The shear rate thinning effect is completely reversible. Something comparable happens in polymer solutions (Section 6.2.2). 

Chang and Zhao23 have compared Newtonian and non-Newtonian analysis of micro-EHD contacts. Based on numerical analysis, it was concluded that the shear thinning effects of the lubricant will produce significant errors if the non-Newtonian behavior is not properly accounted for.23 Effective... 

The low viscosity and the shear thinning effect of liquid crystalline polymers are advantageous for application. For instance, the filling of molded... 

With a lower power-law index, say, n = 0.2, the apparent viscosity would still be close to the limiting shear viscosity at A of 1.6 s and the shear rate of 0.1 s. For these conditions. Cross equation (17.7) gives 77 = T7o/1.23, and Carreau equation (17.8) gives 77 = 770/I.OI. However, at A of 16 s and the shear rate of 10 s (see above), the apparent viscosity would be much lower, that is, the shear thinning effect would be much more pronounced. Both Cross and Carreau equations give 77 = 77o/14,500, that is, 36 times lower apparent viscosity compared to that at n = 0.5. 

Just to give an idea how different are the apparent and true shear rates, we will notice that the higher the shear thinning effect, the larger the difference. For example, at the power-law index n = 0.8, the difference in shear rates and, hence, apparent and true viscosities is 6.25%. For n = 0.2, the difference is 100%. 

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