Ultrasonic emulsification is a process in which two or more incompatible liquids are mixed under the action of ultrasonic energy, with one liquid being uniformly dispersed in the other to form an emulsion-like liquid.
A wide variety of intermediates and consumer products, such as cosmetics and skincare products, pharmaceutical creams, paints, lubricants and fuels, are complete or partial emulsions. Emulsions exist in all aspects of life. Understanding how to control and optimise performance is critical to producing high-quality products, defined as suitable for the final application.
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What is emulsification
The manufacturing process of emulsions varies considerably from industry to industry. These differences include the components used (mixtures, including the various solution), the emulsification method, and the processing conditions. An emulsion is a dispersion of two or more immiscible liquids. High-intensity ultrasound provides the energy required to disperse the liquid phase (dispersed phase) in small droplets of another second phase (continuous phase).
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 an oil-in-water emulsion, where water is the dispersed phase and oil is the continuous phase. It is also possible to create multiple emulsions, including “water-in-oil-in-water” emulsions and “water-in-oil-in-oil” emulsions.
Ultrasonic emulsification process
The phenomenon of cavitation causes ultrasonic emulsification. Ultrasound waves passing through a liquid cause it to compress and expand continuously. The high intensity of ultrasound provides the energy needed to disperse the liquid phase. When the maximum pressure is reached, a liquid rupture occurs when the cohesion is weak. An overpressure follows this rupture at the point where the break occurs, and the presence of some cavities is found. In these cavities, the liquid’s dissolved gas explodes after a short time in the form of bubbles.
To stabilize the newly formed droplets of the dispersed phase and to prevent droplet coagulation. Add emulsifiers (surface active substances, surfactants) and stabilizers to the emulsion. To keep the size and distribution level of the final droplets equal to those in the ultrasonic dispersion zone after breaking.
The ultrasonic frequency and intensity influence the cavitation process. The appearance of cavitation in the body depends mainly on the presence of liquid suspended undissolved gas, the company of which seems to act as a catalyst. The formation of cavities at a specific pressure depends on the development time and ultrasound frequency. The ultrasonic emulsification process represents a competition between opposing processes. Therefore, it is necessary to choose the appropriate operating conditions and frequencies to dominate the destructive effects.
The ultimate sound intensity for the preparation of oil-in-water emulsions is much lower than that for the preparation of water-in-oil emulsions. The type of acoustic field affects the emulsification process, i.e., a certain number of travelling waves are applied. The process efficiency is increased compared to the application of some stationary waves. This can be explained by the fact that in the stationary wave field, the process opposite to dispersion, i.e. coagulation, prevails.
Advantages of ultrasonic emulsification
- Can control the type of emulsion.
- Less power is required to produce emulsions.
- The emulsions formed are more stable, some for several months to more than six months.
- High concentration, pure emulsion concentration can exceed 30%, plus emulsifier up to 70%.
- Low cost, an essential feature of ultrasonic emulsification, can produce very stable emulsions with no emulsifier.
- Compared to general emulsification processes and equipment (such as propellers, colloid mills and homogenisers), ultrasonic emulsification has many advantages.
- The average droplet size of the emulsion formed is small (0.2 to 2 microns), and the droplet size distribution is narrow (0.1 to 10 microns) or narrower.
HCSONIC Emulsification Equipment
HCSONIC wave emulsification equipment can consist of one or more upper kilowatt ultrasonic processors, effectively providing the ability to convert laboratory applications into industrial production, achieving results comparable to today’s best high-pressure homogenisers to obtain finely dispersed emulsions in continuous flow or batches.HCSONIC ultrasonic emulsification equipment is low maintenance and very easy to operate and clean. The ultrasonic emulsification equipment’s power is adjustable and can be adapted to the specific product emulsification requirements.
The device has a replaceable tip tool head (replacement cap) with a hard threaded end attached to the tool head, unscrewed and replaced when the replacement cap wears out due to cavitation.
Note: If you sonicate a solution containing organic solvents, alcohols or any low surface tension liquid, the liquid will seep inside that threaded tip (regardless of the tightness of the connection). Once the fluid enters the end, it will loosen and cause the ultrasonicator to overload. It would help if you used a tip-fixed tooltip used for any model to work with samples containing solvents or low surface tension liquids.
Ultrasonic Emulsification Applications
Ultrasonic emulsification technology has been widely used in food, paper, coating, chemical, pharmaceutical, textile, petroleum, metallurgical and other industrial applications. Ultrasonic equipment can be easily installed in existing production lines, making it easy for manufacturers to upgrade equipment at a lower cost. Ultrasonic emulsification can also create emulsions where typical methods do not work. Standard mixing methods can only create 5% paraffin wax in water; incredibly, 20% more paraffin emulsions can be made with power ultrasound.