Under the action of ultrasonic fluid energy, two or two kinds of incompatible liquids are mixed together, in which the clear body is uniformly sensitive to form an emulsion liquid in another liquid. This processing process is called ultrasonic emulsification .
Various intermediates and consumer products, such as cosmetics and skin care products, pharmaceutical greens, paints, lubricants and fuels are all or part of emulsions. Emulsions exist in all aspects of life. Knowing how to control and optimize performance is essential to produce high-quality products. Quality is defined as being suitable for the final application.
Introduction to Emulsification
Different industries have very different emulsion manufacturing processes. These differences include the components used (mixtures, including various components in the solution), emulsification methods, and more processing conditions. Emulsion is a dispersion of two or more immiscible sea liquids. High-intensity ultrasound is provided to disperse the liquid phase (dispersed phase) in the small droplets of another second phase (continuous phase). energy.
Two liquids can form different types of emulsions, for example, oil and water. First, oil-in-water emulsions, where oil is the dispersed phase and water is the dispersion medium. Second, they can form water-in-oil emulsions, where water is the dispersed phase and oil is the continuous phase. It is also possible to form multiple emulsions, including “water-in-oil-in-water” emulsions and “oil-in-water-in-oil” emulsions.
Ultrasonic cavitation process
Phacoemulsification is caused by cavitation. Ultrasound passing through the slag body causes it to continuously compress and expand. High-intensity ultrasound provides the energy needed to disperse the liquid phase. When the maximum pressure is reached, the liquid ruptures at the point where the cohesion is weaker. After such agglomeration, overpressure appeared at the point where the agglomeration occurred, and some cavities were found. In these cavities, the gas dissolved in the slag body explodes in the form of bubbles after a steady period of time.
In order to stabilize the newly formed dispersed phase liquid sea to prevent coalescence, emulsifiers (surface active substances, surfactants) and stabilizers are added to the emulsion. The final droplet size distribution is maintained at the same level as when the droplets in the ultrasonic dispersion zone are ruptured and distributed.
The cavitation process is affected by the frequency and intensity of ultrasonic waves. The appearance of cavitation in the body depends to a large extent on the presence of undissolved gas in liquid suspension, which seems to act as a catalyst. Under a certain pressure, the formation of the cavity depends to a certain extent on the development time and the ultrasonic frequency. The phacoemulsification process represents a competition between opposing processes. Therefore, it is necessary to choose suitable working conditions and frequencies so that the destructive effect is dominant.
To prepare an oil-in-water emulsion, the ultimate sound intensity is much lower than that of a water-in-oil emulsion. The type of sound field affects the emulsification process, that is, a certain traveling wave is applied. Compared with applying some stationary waves, the process efficiency is improved. This can be explained by the fact that in a static wave field, the opposite process of dispersion, that is, condensation dominates.
Post time:Jul-26-2021