Phase behavior under flow

However, total pressure can be a major effect under conditions where total pressure affects phase behavior or flow conditions or where it may be a driving force in a particular chemical reaction or in diffusion of a particular species in the test environment. In these cases (e.g., where volatile inhibitors or polymeric coatings or seals are being evaluated), it is important to simulate the total pressure so that the proper relationships between liquid and gaseous phases or permeation of corrosive media can be obtained. An example of the effect of total pressure is the performar c o sacrificial anodes under simulated conditions of varying depths of water. 

The aforementioned numerical experiments, namely quasi-static drainage and steady-state flow simulations, are specifically designed to study the influence of microstructure and wetting characteristics on the underlying two-phase behavior and flooding dynamics in the PEFC CL and GDL. 

Phase Behavior of Polymer Blends Under Flow. 72... 

Finally, a challenging problem is to discuss the influence of hydrodynamic flow fields on the phase behavior of polymer blends. This is of fundamental interest and of technological importance as well since stresses and corresponding deformations are encountered during processing of blends. Extension of studies to blend systems under external flow is necessary for the better understanding of structure formation in polymer blends outside equilibrium. 

Before discussing theoretical approaches let us review some experimental results on the influence of flow on the phase behavior of polymer solutions and blends. Pioneering work on shear-induced phase changes in polymer solutions was carried out by Silberberg and Kuhn [108] on a polymer mixture of polystyrene (PS) and ethyl cellulose dissolved in benzene a system which displays UCST behavior. They observed shear-dependent depressions of the critical point of as much as 13 K under steady-state shear at rates up to 270 s Similar results on shear-induced homogenization were reported on a 50/50 blend solution of PS and poly(butadiene) (PB) with dioctyl phthalate (DOP) as a solvent under steady-state Couette flow [109, 110], A semi-dilute solution of the mixture containing 3 wt% of total polymer was prepared. The quiescent... 

The development of improved methods of surfactant design required progress in several other areas (1) understanding the mechanisms of dispersion flow in porous media, to determine which physical properties should be measured, and how their values would affect sweep control (2) measurements of these properties that are valid at the conditions under which the surfactants will be used and (3) understanding of how the values of these parameters depend on phase behavior, molecular structure, and other thermodynamic variables. 

For mechanistic studies, ambient pressure experiments on emulsions and foams often offer significant experimental advantages over high-pressure experiments. However, high-pressure measurements are also needed since the phase behavior, physical properties of the fluids, and dispersion flow may all depend on pressure. Experiments under laboratory conditions that closely match reservoir conditions are particularly important in the design of projects for specific fields. Chapter 19, by Lee and Heller, describes steady-state flow experiments on CO2 systems at pressures typical of those used in miscible flooding. The following chapter, by Patton and Holbrook,... 

The phase behavior of polymer blends under flow was reviewed by Kammer et al. [1993],... 

The effect of a simple shear flow on the phase behavior and morphology was investigated with the use of a parallel-plate apparatus (Fig. 8.4, Madbouly et al. 1999a) for some polymer mixtures poly(methyl methacrylate) (PMMA)/ poly(styrene-co-acrylonitrile) (SAN-29.5) and polystyrene (PS)/poly(vinyl methyl ether) (PVME), which have an LCST-type phase diagram PS/PMMA, which has a UCST-type phase diagram and polycarbonate (PC)/SAN and nylon4, 6(PA4,6)/ poly(phenylene sulfide) (PPS), which are immiscible in the whole measurable region under the quiescent state. 

According to this experimental fact, one can say that the phase behavior of the blend under shear flow can be changed due to the difference in the relaxation time, which reflects the different sensitivities of the cloud point to change under the shear flow. 

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