Effects of solvent evaporation

Apart from the choice of an appropriate stationary and mobile phase, the essential problem for PLC is to attain equilibrium in a three-phase system — between the stationary, mobile, and gas phases. In a nonequilibrated system, the velocity of the mobile phase in a thicker layer (i.e., the effect of solvent evaporation) is less in a lower part of an adsorbent. Such a situation leads to the diffusion of bands and deterioration of the adjacent bands separation. This can be minimized or avoided by prerunning the plate with the mobile phase before spotting of the sample and the saturated chromatographic chambers. 

The dry film thickness h or H is usually the experimentally and readily measured one in industrial practice although techniques are available for measuring the wet film thickness. On the other hand, h or H is the theoretically predicted one. This distinction between wet and dry film thicknesses enables the delineation of effects of solvent evaporation those effects during spinning which are due to a finite Ag and those effects due to post-SCD drying which can be measured by il. ... 

T. H. Young, Y. H. Huang, and L. Y. Chen, Effect of solvent evaporation on the formation of asymmetric and symmetric membranes with crystallizable EVAL polymer. Journal of... 

Meyerhofer (4) examines the problem of spinning a two component system which is composed of solids" and a volatile "solvent". He includes the effect of solvent evaporation and a viscosity which depends on solvent concentration. In this model, the film height decreases with time not only because of the centrifugal pumping, but also because of the evaporation from the surface. As the film is depleted in solvent, the viscosity increases and less fluid is lost because of pumping. Eventually a finite film thickness can be reached because all of the solvent evaporates, and the film consists of only an immobile solid phase. The present analysis is similar to Meyerhofer s. His treatment of the evaporation is corrected, as is his conclusion on the effect of spin speed (which apparently is due to numerical error on his part), and some of his assumptions in developing the equations are relaxed. 

Despite repeated attempts, the data for the mixed solvents are not as precise as should be expected. See, for example, the data for (3n/902)03 shown in Figure 2. Representative data of An versus C2 are given in Figure 3. Since comparable measurements on C(2.43)a were more readily completed, we are at a loss for a definitive explanation for the difficulty experienced with solutions of C(3.00)A in mixed solvents. Possible explanations include the effects of solvent evaporation. Incomplete dissolution of the polymer or (partial) absorption of the polymer on vessel walls during preparation and/or An measurement, in the only direct comparison with published data, we find (9 /902) =... 

Chung TW, Huang YY, Tsai YL, Liu YZ. Effects of solvent evaporation rate on the properties of protein-loaded PLLA and POLL A microspheres fabricated by emnlsion-solvent evaporation process. Journal of Microencapsulation. July-August 2002 19(4) 463-471. PubMed PMID 12396383. 

As mentioned above, the manufactming process leaves aramid fibers with a skin/core structure, reflected in the model of Morgan et al [32]. Apparently, the coagulation creates a differential in density, voidage and fibrillar orientation along the fiber cross section. The fiber surface cools more rapidly, and this, combined with the effects of solvent evaporation, leaves a skin layer with an average thickness between 0.1-0.6 pm, having low... 

Yoo M, Frank CW, Mori S, Yamaguchi S (2004) Interaction of poly(vinylidene fluoride) with graphite particles. 2. Effect of solvent evaporation kinetics and chemical properties of PVDF on the surface morphology of a composite film and its relation to electrochemical performance. Chem Mater 16 1945-1953. doi 10.1021/cm0304593... 

The effects of solvent evaporation were also studied. In these experiments the thickness of the polymer domain was very thin compared to its width and length. The solvent also evaporated into the air very quickly, and its concentration was considered to be unchanged through the depth of the thin film. The decrease in average solvent composition was shown to obqr the relationship [79] ... 

Once the parameters have been determined, the phase separation and effects of solvent evaporation at different spin-coating rotation speeds can be investigated. 

The effect of solvent evaporation has been considered in many studies, which makes the theoretical models more consistent with the experimental results [23, 27, 55-58]. The evaporation of the solvent of the polymer solution alters the rheological properties of the solution, especially for those solutions which have a high latent heat of evaporation. Evaporation also helps in reducing the temperature due to the effective cooling effect inducing shear thinning and elasticity on the polymer film [10]. 

Chen [59] amended Eqs. (10.4) and (10.5) in order to incorporate the effect of solvent evaporation on the spin coating process. This incorporated the effects of mass and momenrnm transfer due to solvent evaporation for quantifying the thickness of the film with respect to the angular velocity, solvent evaporation and viscosity of the solution. The evolved equation can be expressed as... 

Kim et al. studied further the effect of solvent evaporation temperature on the reverse osmosis performance. Butoxy ethanol solution containing 0.5 wt.% SPPO was used as coating solution. Figure 9 illustrates the effect of evaporation temperature on the solute rejection and product permeation flux of the SPPO TFC membranes. The figure shows that the salt rejection increased while the product permeation flux decreased when the... 

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