Shear environment

Retention aid polymers are used in a very high shear environment, so floe strength and the abiHty for floes to reform after being sheared (43) is important. The optimum floe size is a compromise. Larger floes give better free drainage, but tend to produce an uneven sheet due to air breakthrough in... 

The mechanism of formation of morphology structures in iPP-E-plastomers blends via shear-dependent mixing and demixing was investigated by optical microscopy and electron microscopy. A single-phase stmcture is formed under high shear condition in injection machine after injection, namely under zero-shear environments, spinodal decomposition proceeds and leads to the formation of a bicontinuous phase stmcture. The velocity of spinodal decomposition and the phase separation depend on the molecular stmcture of iPP and E-plastomer components. 

Holay, S. H. and Harper, J. M. (1982). Influence of the extrusion shear environment on plant protein texturization. J. Food Sci. 47,1869-1874. 

The front jet produces a countercurrent shear environment which entrains reactants and pumps them radially inward toward the flame as depicted in the sketch of Fig. 17.3a. Since the reactants are premixed, the flame sheet must reside at a position where the flame speed (determined by the reactant equivalence ratio and the local turbulence intensity) matches the radial inward velocity of reactants. Since the radial velocity must be zero at the cylinder axis and wall, a maximum must exist (as indicated in Fig. 17.36). As long as the flow rates are maintained at high enough rates, this maximum is greater than the local flame speed and the flame remains confined. If the flame speed exceeds the maximum radial velocity anywhere along the axis of the cylinder, the flame changes modes and flashes out to the cylinder wall. 

Table V illustrates the results obtained by the experimental technique which essentially simulates injection molding while satisfying the time-temperature conditions effective in the fabric laminate work. The large strength increases were reduced to only approximately 10% over the bare glass controls. The conclusion is that the high shear environment of injection molding which yields discontinuous fibers does not allow the same strength increases obtained in earlier experimental work.

High density charring ablators such as carbon-phenolic contain high density reinforcements to improve shear resistance. In contrast, lower density charring ablators as a rule are used for low shear environments. Hie Apollo mission reentry conditions are typical of a relatively low shear environment, so low density ablators consisting of epoxy—novolac resin containing phenolic microballoons and silica fiber reinforcement have been used. In order to improve the shear resistance and safety factor of the material for this mission, the ablator was injected into the cavities of a fiberglass -reinforced phenolic honeycomb that was bonded to the substructure of the craft (48). 

These findings suggest that the shear-protective effects of these additives in the bioreactor are physical in nature, and specifically purely fluid-mechanical, i.e. due to changes in the interactions between bubbles, draining films and the cells. If their effect was biological, cells would have been protected in both shear environments (viscometer and bioreactor). Other experiments suggest that the protection mechanism may vary for different cell types. 

In a shear environment, elastomers, and in particular EPM elastomers, show only a moderate viscosity decrease as the temperature... 

Polymers are used for mobility control in chemical flooding processes such as micellar-polymer and caustic-polymer flooding and in polymer augmented waterflooding. Selection of a polymer for mobility control is a complex process because it is not possible to predict the behavior of a polymer in porous rock from rheological measurements such as viscosity/ shear rate curves. Polymers used for mobility control are non-Newtonian fluids. Flow characteristics are controlled by the shear field to which the polymer is subjected. Properties of polymers can be measured under steady shear in rheometers. However, in porous rock, it is difficult to define the shear environment a polymer experiences as it flows through tortuous pores. 

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