Emulsions continued coalescence

Oiling out Continued coalescence of lipid emulsion particles, resulting in irreversible separation of the emulsion (or breaking of the emulsion). 

They added a small quantity of highly colored drops to the reactor which otherwise contained only uncolored drops dispersed in the continuous phase. As the color is spread more uniformly about the whole dispersed phase by continuous coalescing and redispersion, the light transmission of the emulsion is decreased according to... 

Dried films are not likely to be continuous in either case. Dried films do not tend to coalesce unless heated above the of the endblock domains. Heating causes the endblock domains to soften which allows the individual particles deposited from the emulsion to coalesce. Continuous films are not always necessary for adequate performance, and endblock coalescence is not needed in these cases. 

Emulsion polymerization also has the advantages of good heat transfer and low viscosity, which follow from the presence of the aqueous phase. The resulting aqueous dispersion of polymer is called a latex. The polymer can be subsequently separated from the aqueous portion of the latex or the latter can be used directly in eventual appUcations. For example, in coatings applications-such as paints, paper coatings, floor pohshes-soft polymer particles coalesce into a continuous film with the evaporation of water after the latex has been applied to the substrate. 

If, by one of the above procedures, a few or even many bubbles have been introduced into a liquid, there is still no foam. In a foam, films between the bubbles are thin otherwise, the system is a gas emulsion. How, then, can a true foam be achieved If it is assumed that, because of some kind of stirring, two bubbles move to meet each other and the liquid layer between them gets thinner and thinner and if this process continues for a sufficient time, the two bubbles will touch and, eventually, coalesce. Many such encounters would destroy the foam. It is clear, therefore, that bubbles should be free to approach each other closely, but should be unable to cross the last short fraction of the initial distance. 

The archetypal, stagewise extraction device is the mixer-settler. This consists essentially of a well-mixed agitated vessel, in which the two liquid phases are mixed and brought into intimate contact to form a two phase dispersion, which then flows into the settler for the mechanical separation of the two liquid phases by continuous decantation. The settler, in its most basic form, consists of a large empty tank, provided with weirs to allow the separated phases to discharge. The dispersion entering the settler from the mixer forms an emulsion band, from which the dispersed phase droplets coalesce into the two separate liquid phases. The mixer must adequately disperse the two phases, and the hydrodynamic conditions within the mixer are usually such that a close approach to equilibrium is obtained within the mixer. The settler therefore contributes little mass transfer function to the overall extraction device. 

In terms of measuring emulsion microstructure, ultrasonics is complementary to NMRI in that it is sensitive to droplet flocculation [54], which is the aggregation of droplets into clusters, or floes, without the occurrence of droplet fusion, or coalescence, as described earlier. Flocculation is an emulsion destabilization mechanism because it disrupts the uniform dispersion of discrete droplets. Furthermore, flocculation promotes creaming in the emulsion, as large clusters of droplets separate rapidly from the continuous phase, and also promotes coalescence, because droplets inside the clusters are in close contact for long periods of time. Ideally, a full characterization of an emulsion would include NMRI measurements of droplet size distributions, which only depend on the interior dimensions of the droplets and therefore are independent of flocculation, and also ultrasonic spectroscopy, which can characterize flocculation properties. 

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