Emulsion is a mixture of substances. In it, one component consists of tiny particles that are insoluble in the other. This ingredient is called "dispersed phase". Another substance is a dispersed medium. It contains the first component. "Emulsion" is a term of Latin origin. In translation, it means "I milk, I milk." Let's consider this concept in more detail.
General information
Any two liquids that do not mix and do not react chemically can be emulsified. One of the components is almost always water. Another substance consists of weakly polar or neutral molecules (for example, fats). The first known emulsion is milk. Here the fat particles are dispersed in water. The size of the smallest particles of the dispersed phase is 1-50 microns, so emulsions are classified as coarse systems. Low-concentration liquids - unstructured. Mixtures with high concentration - structured. According to thermodynamic features, an oil emulsion is an unstable system. The size of the phase droplets is large, and the mixture will be unstructured.
Classification
The type of emulsion obtained depends on the ratio of phase volumes and their composition, onthe amount and nature of the emulsifier, its chemical activity, the method and method of mixing.
- Direct mixtures with the smallest particles of non-polar and insoluble liquid in the polar phase (o/w - from the expression "oil in water"). For such mixtures, emulsifiers that dissolve in water, such as bitumen particles, can be used. Their molecules are adsorbed on the surface films of the m-phase, reducing not only the tension, but also creating a strong film.
- Reverse (w / m) mixtures for which water-insoluble emulsifiers are used.
Chemical action on the emulsion, pressure, composition change can lead to inversion.
- Lyophilic emulsion is a mixture that forms spontaneously, spontaneously. It is considered to be thermodynamically stable. An example is critically stable emulsions when the temperature limit for phase mixing is reached. Lubricating oils and cooling fluids also fall into this category.
- Lyophobic emulsion is a mixture formed by mechanical, acoustic or electrical mixing. Thermodynamically, they are extremely unstable. Such mixtures without emulsifiers do not exist for a long time. Good ingredients for them: Surfactants, macromolecular, water-soluble substances, solids with high dispersion.
Receive
There are two emulsion production technologies. The first is the way of fine crushing of fractions. The second is the process of film formation followed by rupture into small pieces. In the first variant, the substance is slowly added todispersed system. In this case, it is necessary, while carrying out the addition, to constantly mix at high speed. In this case, the quality of the mixture will depend on various factors. In particular, on the speed of mixing, introduction and volume of the dispersible substance, its concentration, temperature and acidity of the medium. The second method is a process in which a film is formed on the surface of another phase. Air is blown in from below. The bubbles break the film into small drops and mix the entire volume of the liquid. In our time, they began to use ultrasound instead of air. This causes the film to break into even smaller pieces.
Destruction of mixtures
Over time, spontaneous disintegration of the emulsion occurs. There are cases when it is necessary to speed up this process and reduce the concentration of the compound. This need is relevant when the presence of a highly concentrated emulsion interferes with the processing of the material or its correct application. There are several ways to speed up the process of reducing the concentration of the solution:
- Chemical method. Reagents are used that destroy the surface films of the emulsifier itself. In this case, the negative charge concentrated on the surface film is neutralized. The use of organic additives of dietary supplements (biologically active substances - demulsifiers) is based on the same principle.
- Adding an emulsifier that causes the formation of cations that attract a negative surface charge and cause destabilization of the surface films of the emulsifier. The stability of the state of the solution decreases.
- Replacement of the emulsifier with another surface-active component (surfactant). It dilutes the concentration of the former, but does not itself form a strong enough film.
- Thermal method. With this method, the emulsion is exposed to temperature, which causes it to separate.
- Mechanical method. This option is also called the separator method. The emulsion is slowly pumped into a container rotating at a high angular velocity. The solution is broken down into components by weight fractions.
- Method of applying electric current or adding an electrolyte to the emulsion. This method destroys the surface films of mixtures stabilized by a negative charge.
Application
The range of application of emulsions in industry is very wide. Specifically, connections use:
- In the production of margarine and butter.
- In soap making.
- When making natural rubber materials.
- In construction. For example, bituminous emulsion is a non-combustible compound.
- In agriculture: pesticides - various drugs that destroy plant pests.
- For medical purposes: making various medicines, ointments, cosmetics.
- Various emulsion paints are used in painting.
- Cosmetics for hair, emulsions that protect the surface of the hair during dyeing. For example, a developing emulsion (this is an oxidizing agent for paint).
- The oil industry uses a mixture of water and oil,in which the dispersion of one liquid phase into another occurs in tiny droplets - globules.
