Effect of Shearing

Similarly, Jiao also observed the interfacial roughening in a system consisting of polystyrene/benzyl amine end-capped polystyrene/styrene-maleic anhydride random copolymer. He proposed that a microemulsion was formed when the interfacial tension was driven negative by the graft copolymer formed at the interface [72]. 

These experiments, carried out under static conditions, can explain that the fast interface generation observed by Orr et al. under dynamic conditions (high shearing) is directly related to the reaction induced roughening of the interface which magnifies the effect of the physical mixing. 

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Effect of Shear. Concentrated aqueous solutions of poly(ethylene oxide) are pseudoplastic. The degree of pseudoplasticity increases as the molecular weight increases. Therefore, the viscosity of a given aqueous solution is a function of the shear rate used for the measurement. This relationship between viscosity and shear rate for solutions of various molecular weight poly(ethylene oxide) resins is presented in Figure 8. 

Fig. 8. Effect of shear on aqueous solution viscosities of poly (ethylene oxide) resins (a) 1.0 wt % solution, (b) 5.0 wt % solution (10). Each curve...

Table 6.4 Effect of shear stress on melt viscosity ...

Another possibility is that the effect of shear may be localized, e.g. at the wake of bubbles which is independent of the gas flow rate. Tsutsumi etal. 

Figure 7 Effect of shearing history on swelling ratio for HP LDPE sample (A) Brabender worked at 190°C (A) solvent treated sample. Source Ref. 39.

Viscosity of surfactant solutions depends on the kind of solution, shear rate, temperature and concentration. Figure 2.51 shows the effect of shear rate U5 on shear... 

Another widely used concept is that of a planetary boundary layer (PBL) in contact with the surface of the Earth above which lies the "free atmosphere." This PBL is to some degree a physically mixed layer due to the effects of shear-induced turbulence and convective overturning near the Earth s surface. 

Fig. 26. The effect of shear on a range of enzymes with a stainless steel disc at a mean velocity gradient of 6490 s at 30 °C, in the presence of an air/liquid interface. Each data point in the figure is the mean value of 4 replicates and is given as a percentage of the control value [107]...

In this volume not all stress types are treated. Various aspects have been reviewed recently by various authors e.g. The effects of oxygen on recombinant protein expression by Konz et al. [2]. The Mechanisms by which bacterial cells respond to pH was considered in a Symposium in 1999 [3] and solvent effects were reviewed by de Bont in the article Solvent-tolerant bacteria in biocatalysis [4]. Therefore, these aspects are not considered in this volume. Influence of fluid dynamical stresses on micro-organism, animal and plant cells are in center of interest in this volume. In chapter 2, H.-J. Henzler discusses the quantitative evaluation of fluid dynamical stresses in various type of reactors with different methods based on investigations performed on laboratory an pilot plant scales. S. S. Yim and A. Shamlou give a general review on the effects of fluid dynamical and mechanical stresses on micro-organisms and bio-polymers in chapter 3. G. Ketzmer describes the effects of shear stress on adherent cells in chapter 4. Finally, in chapter 5, P. Kieran considers the influence of stress on plant cells. 

S. Vitthal and J. M. McGowen. Fracturing fluid leakoff under dynamic conditions Pt 2 Effect of shear rate, permeability, and pressure. In Proceedings Volume, pages 821-835. Annu SPE Tech Conf (Denver, CO, 10/6-10/9), 1996. 

We have created structured networks in whey proteins using mild heat and shear, to create reversible TWPs. By understanding on a molecular basis, the effects of shear, ways of creating new functionality can be developed. This will enable development of extrusion parameters that permit controlled denaturation of whey proteins. 

Y. A. Antonov, P. Van Puyvelde, P. Moldenaers 2004, (Effect of shear flow on the phase behavior of an aqueous gelatin-dextran emulsion), Biomacromolecules 5, 276. 

KS Murthy, JC Samyn. Effect of shear mixing on in vitro drug release of capsule formulations containing lubricants. J Pharm Sci 66 1215-1219, 1977. 

Why does the effect of shear stress decrease as the distance from the surface at which the shear stress is imposed increases ... 

Chang, H.D., Darby, R. "Effect of Shear Degradation on the Rheological Properties of Dilute Drag Reducing Polymer Solutions," J. Rheol.. 1983, 27(1), 77-88. 

Gardner, D.C. and Eikerts, J.V. "Effects of Shear and Proppant on the Viscosity of Crosslinked Fracturing Fluids," SPE paper 11066, 1982 SPE Annual Fall Technical Conference and Exhibition, New Orleans, September 26 29. 

Clarke, N. Effect of Shear Flow on Polymer Blends. Vol. 183, pp. 127-173. 

Great care has to be given to the physics of rotation and to the treatment of its interaction with mass loss. For differentially rotating stars, the structure equations need to be written differently [9] than for solid body rotation. For the transport of the chemical elements and angular momentum, we consider the effects of shear mixing, meridional circulation, horizontal turbulence and in the advanced stages the dynamical shear is also included. Caution has to be given that advection and diffusion are not the same physical effect. 

Figure 6. Effect of shear on the average film thickness of PS-8. See Figure 2 for symbols.

Particle collision frequency due to Brownian motion was estimated to be less than 1% of the collision frequency due to shear. The effects of Brownian motion could therefore be neglected in the flocculation rate calculations. However, for the smallest molecular size, radius of gyration 14 nm (see Table I), the effect of Brownian motion on the particle-polymer collision efficiency was of the same order of magnitude as the effect of shear. These two contributions were assumed to be additive in the adsorption rate calculations. Additivity is not fundamentally justified (23) but can be used as an interpolating... 

High shear forces are prevelant in the approach flow system to the paper machine (i.e. as the fibre suspension approaches the point of deposition on the wire), and these have a large impact upon the efficiency of retention aids (Figure 7.8). A study of the effect of shear can often be helpful in establishing the mechanism of retention. Bridging flocculation is irreversibly sensitive to shear (i.e. when the shear forces are removed the suspension does not reflocculate) whereas charge neutralisation is reversibly sensitive to shear. 

Figure 7.8 The effect of shear forces (pre-stirring for different times) on the optimum polymer dose for ionene halide retention aids.

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