Water emulsion - what is it?
Emulsions are sometimes called a variety of colloidal solutions. Basically, they are a combination of at least two liquids, usually not miscible under natural conditions. In this case, one of the liquids has a dispersed phase, and the second forms a continuous liquid medium( the dispersion phase).Examples of such liquids are numerous, and they are widely found in everyday life: photographic solutions, cooling emulsion liquids for metalworking, mayonnaise, milk, and many others.
Two liquids are able to form different types of emulsions, depending on which one is the dispersed( suspended) phase, and which forms the dispersion medium, as the basis of the emulsion composition. As an example, you can bring a liquid such as water, and such an oil refining product as oil.
With a solution type m / v( oil in the dispersed phase, and water in the dispersion phase), such an aqueous emulsion is called a straight line. If the dispersed phase is formed by water and the oil is the main dispersion composition, then the emulsion is considered to be inverse, the type is denoted in / m.
By the way, ordinary milk is a direct emulsion( m / in).More complex are compositions that are in the form of w / m / in or m / m / m( i.e., water-oil-water and oil-water-oil).
Emulsion treatment - the principle of formation and use of
The compositions of the same emulsions may have a greater or lesser degree of concentration. Most of them are opaque. When light passes( even through aqueous emulsions of oil products), its uniform dispersion determines the white color of the compositions. If the liquid concentration of the disperse phase is lowered, the color becomes bluish, and at high concentrations the spectrum shifts toward yellow.
Thus, even visually it is possible to control the quality and composition of the emulsion. For a new generation of solutions created by nanotechnology on special equipment, the translucency associated with the size of the droplet particles is more characteristic.
Solutions obtained with the use of surfactants are often called microemulsions. Such compositions are not so stable, they are often arbitrarily decomposed, they restore the initial state of the components. An example can lead any housewife, who cooked a vinaigrette dressed with oil and vinegar. The peculiarity of such compositions is their thermal stability, nanoemulsions have kinetic stability.
Application in the construction of aqueous emulsions is quite popular. Hydrophobiziruyuschie compositions are applied to any surface, ranging from concrete and fibrocemental structures, ending with natural stone. It is also possible to impart a hydrophobizing property to a coating of paint and plaster. Such aqueous emulsions contain highly alkylated products, for example alkoxysiloxane and fluoropolymer.
With a certain chemical composition, such aqueous emulsions are able to protect the surface not only from moisture, but also contaminants, even oil stains. The ability to fasten the surface is also seen, protecting it from cracks and chips. The essence of the action is simple, because after application the water evaporates, leaving a strong polymer film on the surface.
Echoes of the use of aqueous emulsions can also be found in paints. Thus, silicone resin in the composition of its aqueous emulsion is used as a reliable binder for coating with silicone paint of mineral bases, the most famous example of which is cement. In the same way, it is also used in polymer dispersions, the most widely used of which is styrene-acrylate.
There are also examples in the automotive industry: without lubricating and cooling emulsions, no car will appear on the road. Roads, by the way, are built on the basis of bituminous binding materials, which are emulsions. If you completely dehydrate the gasoline, it will not burn in the cylinder chamber of the engine( a proven fact).In the production of pesticides for agriculture, such solutions are also widely used. And this list can be continued.
Preparation of an aqueous emulsion
It is rather difficult to create an emulsion with a long period of steady state. But the use of special surface-active substances, called emulsifiers, facilitates the creation of stable emulsions of those liquids that are difficult to dissolve in each other. Substances emulsifiers contribute to the appearance of a dispersed phase in the corresponding liquid. Of course, the type will depend also on the volume fractions of the mixed compositions.
But as emulsifying compounds are selected such substances that do not dissolve so well in the dispersed liquid, contributing to the creation of an appropriate phase. Examples include proteins that are poorly soluble in oil and better soluble in water. They contribute to the better formation of direct emulsion m / v.
The main methods for obtaining a homogeneous emulsion consist in the gradual addition of a mixture of surfactant and dispersed component to a constant, dispersive component, with enhanced stirring of the latter. Passing air bubbles through the main component, causing it to "boil", add a dispersed component and p-active substances. In a second way, homogeneous emulsion formulations are also obtained.
Over time, the stability of emulsions decreases. There is decomposition and stratification into components. The reason may be the force of attraction of dispersed droplets, outwardly it manifests itself in the form of falling out of "flakes".The different density results in the dispersed substance rising into the top layer of the emulsion, etc. As a rule, surfactants impart more stability, affecting the dimensional stability of dispersed droplets.
When and how can I destroy the emulsion compound? First of all, the destruction of emulsifier films is promoted by the corresponding chemical substances - reagents. With their help adsorption of emulsifiers or their replacement takes place.
Heating can help, as a rule, leading to their rapid stratification. Mechanical methods of separation of compositions are known due to different component densities( centrifuges).It is possible to achieve separation by electrolytes, the action of electric current, etc.
