Dispersing liquids

C2.2.4.5 POLYMER DISPERSED LIQUID CRYSTAL (PDLC) DISPLAYS... 

Figure C2.2.14. Principle of operation of a polymer-dispersed liquid crystal display. The contours of the liquid...

Simoni F 1997 Nonlinear Optical Properties of Liquid Crystals and Polymer-Dispersed Liquid Crystals (Singapore World Scientific)... 

Fits some, but not all, data. Low mass transfer rate. = mean molecular weight of dispersed phase tf= formation time of drop. k[, i = mean dispersed liquid phase M.T. coefficient kmole/[s - m" (mole fraction)]. 

T] Use with log mean mole fraction differences based on ends of column, t = rise time. No continuous phase resistance. Stagnant drops are likely if drop is very viscous, quite small, or is coated with surface active agent. A.y uiean dispersed liquid M.T. coefficient. 

The depth of dispersed liquid h accumulating on each plate is determined by the pressure drop required for flow of the hquids,... 

Phase Dispersed There is an ill-defined upper limit to the volume fraction of dispersed liquid which may be maintained in an agitated dispersion. For dispersions of organic liquids in water [Quinn and Siglon, Can.J. Chem. Eng., 41, 15 (1963)],... 

In general, when sepiarating two liquids, they must be immiscible and have different spiecific gravities before a separation technique-such as oil/water separation-would be effective. In the case of finely dispersed liquids or finely dispersed solids, if the dispersed material is below one micron in particle size, centrifuging should be considered. The use of centrifugal force on the differing densities of the material can facilitate the separation technique. 

Emulsions. Emulsions are formed when one liquid is dispersed as small droplets in another liquid with which the dispersed liquid is immiscible. Mutually immiscible fluids, such as water and oil, can be emulsified by stirring. The suspending liquid is called the continuous phase, and the droplets are called the dispersed (or discontinuous) phase. There are two types of emulsions used in drilling fluids oil-in-water emulsions that have water as the continuous phase and oil as the dispersed phase, and water-in-oil emulsions that have oil as the continuous phase and water as the dispersed phase (invert emulsions). 

Suspension polymerization produces polymers more pure than those from solution polymerization due to the absence of chain transfer reactions. As in a solution polymerization, the dispersing liquid helps control the reaction s heat. 

Gas dispersion, liquid-liquid contacting, some heat transfer, etc. 0.6... 

Similar behaviour has been observed by Emerson and Zannoni [112] in their simulations of polymer dispersed liquid crystal droplets where the solid... 

WiLLE, C., The potential of micromixers for contacting of disperse liquid phases,... 

Haverkamp, V., Ehreeld, W, Gebauer, K., Hessel, V., Lowe, H., Richter, T, WiLLE, C., The potential of micromixers for contacting of disperse liquid phases, Fresenius J. Anal. Chem. 364 (1999) 617-624. 

Stirrer design D/Dr (m/s) (Pas) Baffled Heat transfer Wall Coil Gas-liquid dispersion Liquid-solid dispersion... 

VII. TECHNIQUES BASED ON DISPERSED LIQUID-LIQUID SYSTEMS... 

Decanters are used to separate liquids where there is a sufficient difference in density between the liquids for the droplets to settle readily. Decanters are essentially tanks which give sufficient residence time for the droplets of the dispersed phase to rise (or settle) to the interface between the phases and coalesce. In an operating decanter there will be three distinct zones or bands clear heavy liquid separating dispersed liquid (the dispersion zone) and clear light liquid. 

Centrifugal pumps are effective inline mixers for blending and dispersing liquids. Various proprietary motor-driven inline mixers are also used for special applications see Perry et al. (1997). 

Figure 8.1b shows a simple gravity settler or decanter for removing a dispersed liquid phase from another liquid phase. The horizontal velocity must be low enough to allow the low-density droplets to rise from the bottom of... 

To produce novel LC phase behavior and properties, a variety of polymer/LC composites have been developed. These include systems which employ liquid crystal polymers (5), phase separation of LC droplets in polymer dispersed liquid crystals (PDLCs) (4), incorporating both nematic (5,6) and ferroelectric liquid crystals (6-10). Polymer/LC gels have also been studied which are formed by the polymerization of small amounts of monomer solutes in a liquid crystalline solvent (11). The polymer/LC gel systems are of particular interest, rendering bistable chiral nematic devices (12) and polymer stabilized ferroelectric liquid crystals (PSFLCs) (1,13), which combine fast electro-optic response (14) with the increased mechanical stabilization imparted by the polymer (75). 

Figure 1.20 Encapsulation of microdroplets of liquid crystals in ORMOSIL matrices results in materials with better transparency and thermal stability than polymer-dispersed liquid crystals. Gel-glass dispersed liquid crystal device switched between the OFF and ON state (thickness 10 pm, 4 x 2 cm, Fp p = 90V). (Reproduced from ref. 45, with permission.)...

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