emulsion

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Related to Emulsions: Emulsifying agent, Colloids

emulsion:

see colloidcolloid
[Gr.,=gluelike], a mixture in which one substance is divided into minute particles (called colloidal particles) and dispersed throughout a second substance. The mixture is also called a colloidal system, colloidal solution, or colloidal dispersion.
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Emulsion

 

a disperse system consisting of droplets of a liquid (the dispersed phase) distributed evenly throughout another liquid (the dispersion medium).

A distinction is made between emulsions of the oil-in-water type (with droplets of a nonpolar liquid, such as a mineral oil, dispersed in a polar medium, usually water) and reverse emulsions of the water-in-oil type (with droplets of a polar liquid in a non-polar medium). Multiple emulsions are also encountered, in which the droplets of the dispersed phase serve as the dispersion medium for even finer droplets of another dispersed phase.

Emulsions are also divided into lyophilic and lyophobic types (seeLYOPHILIC AND LYOPHOBIC COLLOIDS). Lyophilic emulsions are thermodynamically stable, reversible systems that are formed spontaneously at temperatures close to the critical displacement temperature for two interacting liquids. Lyophobic emulsions are thermodynamically unstable systems formed by the mechanical, acoustic, or electrical dispersion of one liquid in another or by the separation of droplets from a supersaturated solution or melt; such emulsions may exist for prolonged periods only if mixed with an emulsifier. Lyophilic emulsions are highly dispersed (colloidal) systems, the droplets of which measure no more than 10–5 cm. Lyophobic emulsions are coarsely (poorly) dispersed systems with droplet size usually ranging from 10–5 to 10–2 cm. If the dispersed phase and dispersion medium differ greatly in density, the emulsion will be kinetically unstable—that is, the particles of the dispersed phase will tend either to sink to the bottom or rise to the top. The sedimentation of emulsion droplets that are well protected against coalescence may lead to the concentration of the droplets and the formation of creams or sediments of continuous two-liquid phases not separated into discrete layers.

The type and properties of an emulsion depend on such factors as its composition, the relative proportions of the liquid phases, the quantity and chemical nature of the emulsifier, the method of emulsification, and the temperature at which the emulsification is carried out. A change in the composition of an emulsion or in the action of the emulsifier may produce a phase inversion, in which an oil-in-water emulsion becomes a water-in-oil emulsion or vice versa.

Dilute emulsions are typical liquids, with droplets that move freely and independently of one another in a highly mobile medium. In emulsions with droplets of uniform size, as the concentration of the dispersed phase exceeds 74 percent by volume, the viscosity of the system increases abruptly, and the emulsion becomes a gel. In the process, droplets that initially had a spherical shape are highly deformed in such a way that they come to resemble polyhedrons. The content of the dispersed phase in highly concentrated emulsions may be as high as 99 percent by volume; in such cases, the dispersion medium is retained between the droplets in the form of fine layers that resemble the liquid films between bubbles in foams.

Emulsions with various compositions and properties are commonly used in industry, agriculture, and medicine; they also have household uses. Many foods, such as milk and egg yolks, are multicomponent emulsions, as are unrefined petroleum and the milky juices of plants.

Among the products that take the form of emulsions are cooling lubricants and various pesticides, cosmetics, drugs, and binders for latex paints. Asphalt emulsions are used in construction.

REFERENCES

Voiutskii, S. S. Kurs kolloidnoi khimii, 2nd ed. Moscow, 1975. Pages 367–81.
Emul’sii. Leningrad, 1972. (Translated from English.)
Becher, P. Emulsions: Theory and Practice, 2nd ed. New York, 1965.
Emulsions and Emulsion Technology, parts 1–2. Edited by K. J. Lissant. New York, 1974.

L. A. SHITS

emulsion

[ə′məl·shən]
(chemistry)
A stable dispersion of one liquid in a second immiscible liquid, such as milk (oil dispersed in water).
(graphic arts)
In photography, the photosensitized material on film, plates, and various photographic papers.

emulsion

1. A mixture of liquids insoluble in one another, in which one is suspended in the other in the form of minute globules.
2. A mixture in which solid particles are suspended in a liquid in which they are insoluble, as a mixture of bitumen and water, with uniform dispersion of the bitumen globules. The cementing action needed in roofing and waterproofing takes place as the water evaporates.

emulsion

emulsionclick for a larger image
A suspension of a light-sensitive silver salt, especially silver chloride or silver bromide in a colloidal medium—usually gelatin—which is used for coating photographic films, plates, and paper.

emulsion

1. Photog a light-sensitive coating on a base, such as paper or film, consisting of fine grains of silver bromide suspended in gelatine
2. Chem a colloid in which both phases are liquids
3. a type of paint in which the pigment is suspended in a vehicle, usually a synthetic resin, that is dispersed in water as an emulsion. It usually gives a mat finish
4. Pharmacol a mixture in which an oily medicine is dispersed in another liquid
References in periodicals archive ?
Egg albumen plays an important role in the process of dispersion in producing stable, oil-based emulsions [23, 24].
The water resistance increases with the increasing emulsion content, however the explosive power per pound will generally decrease as the emulsion content is increased.
Emulsion and gel could be mixed in preparation called emulgel,5 O/W emulsion for lipophilic materials while W/O for hydrophilic materials.
These calculators take into account things like the size of the walls, windows and doors, but not the type of emulsion you're using or the state of the walls themselves.
It appears that measuring electrical conductivity could be potentially used to predict the particle size and stability of emulsions.
BME also pointed out that with double-salt formulation, the emulsion has a lower "fudge" point than single-salt emulsions, which means that the temperature required in the manufacturing process can be lower without crystals forming.
According to the results of studies of the effect of the fuel phase on the rheological parameters of emulsions and the nature of their thermal decomposition the compounds of the fuel phase (the dispersion medium) of energy condensed packaged emulsion systems have been developed.
Western Emulsions is a a supplier of branded and standard asphalt emulsions, and raw asphalt used for pavement preservation, repair and restoration projects.
The formation, selection and stabilization of emulsions along with the control of their properties on an application represent a challenge in almost all process industries.
The most rapid gains through 2016 will be for emulsion polymers in paint and coatings, where water-based formulations are steadily increasing their share of the market.
The second one is the CFS EcoCut CAP 2 on the stand which is a fully automated multifunctional emulsifier, which continuously produces extremely stable emulsions with a wide range of granulation.
Low-emission paints, on the other hand, are formulated without solvents or plasticizers because they use binders like VAE emulsions that allow excellent film formation at low temperatures without the need for solvents or plasticizers.