Influencing Factors And Advantages Of Ultrasonic Emulsification Equipment For Making Emulsion

An emulsion is a dispersion of two immiscible liquids, one of which is dispersed in the other in the form of fine droplets or particles, forming a mixed liquid. The process of dispersing one immiscible liquid in another immiscible liquid is called emulsification. The formation of emulsions requires the necessary process of liquid emulsification, which uses mechanical shear to break up the dispersed phase of large droplets in the continuous phase.

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Ultrasonic emulsification is a technical means of emulsification, that is, high-frequency vibration is applied to the tool head through an ultrasonic transducer, so that two immiscible liquids are mixed to form an emulsion. Compared to traditional emulsification techniques, i.e. ordinary mechanical stirring, sonication can generate droplets of smaller size, and phacoemulsification typically requires lower amounts of surfactant to provide a stable emulsion than other techniques.

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Factors Affecting Ultrasonic Emulsification

Various factors that affect and control sonication include ultrasonic power, time, sonication frequency, and emulsion temperature.

sound frequency

The frequency of 20 to 40 kHz produces the best emulsification, that is, at lower frequencies, the shear force has a greater effect on the emulsification. As the ultrasonic frequency increases, the time required for the bubbles to expand and collapse decreases, thereby reducing the degree of shearing. At higher frequencies, the cavitation threshold increases and the sonication process is less efficient as more power is required to initiate cavitation. Ultrasonic emulsification equipment can be selected from 20 to 40 kHz frequency, and different frequency tool heads can be selected according to the specific application.

Ultrasonic power

Ultrasonic power is one of the main factors controlling the emulsion emulsification efficiency. As the ultrasonic power increases, the droplet size of the dispersed phase decreases. However, when the power input is greater than 200 W, the smaller emulsion droplets aggregate into larger droplets. This is because of the large number of cavitation bubbles, extremely high energy density, increased droplet concentration, and high rates of collisions between droplets under these conditions. Therefore, it is very important to determine the optimal power during phacoemulsification. As the homogenization time increases, the generation of small droplets also increases. At the same energy density, the two emulsification techniques can be compared to examine their efficiency in stable emulsion formation.

Solution temperature

During phacoemulsification, a moderate increase in solution temperature results in a decrease in the interfacial tension and viscosity of the solution, making it easier to mix, and increasing the number of cavitation bubbles. These trends are very beneficial to the overall emulsification process. However, the effect of continuously increasing temperature on emulsification can also be detrimental: the number of cavitation nuclei increases with increasing temperature, and the air pressure inside the bubbles also increases, resulting in the attenuation of the shock wave and the creation of a large number of bubbles. This reduces the maximum pressure reached when the bubble implodes. Due to the increased amount of evaporation in the bubbles, the collapse of the bubbles becomes less violent, which leads to reduced shear forces and emulsification efficiency.

Sonication time

In general, an increase in phacoemulsification time results in a decrease in the size of the dispersed phase droplets. Over time, the amount of ultrasonic energy in the solution also increased, resulting in an increase in the number of broken droplets and a decrease in the size of the emulsion droplets. However, beyond a certain processing time, ie, exceeding the optimal processing time, smaller droplets will coalesce into larger droplets due to the prevalence of high droplet concentrations and collisions between droplets.

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Advantages of Ultrasonic Emulsification

Unlike traditional emulsification techniques and equipment, the benefits of phacoemulsification are obvious.

Improve emulsification effect

Depending on the droplet size of the dispersed phase, emulsions can be classified into microemulsions (10–100 nm), nanoemulsions (100–1000 nm), and macroemulsions (0.5–100 μm). Ultrasound is an effective method to reduce the particle size of dispersions and emulsions. Ultrasonic emulsification equipment can obtain emulsions with small particle size (only 0.2–2 μm) and narrow droplet size distribution (0.1–10 μm), and the use of emulsifiers can also increase the concentration of the emulsion by 30% to 70%.

Enhanced emulsion stability

Essentially, emulsions are kinetically unstable, do not form spontaneously, and separate into their constituent phases if their stability is not controlled. Therefore, in order to stabilize the newly formed droplets of the dispersed phase against coalescence, emulsifiers and stabilizers are added to the emulsion. Phacoemulsification requires little or no emulsifier to obtain stable emulsions. After sonication, the emulsion can remain stable for several months or more than half a year.

Control the type of emulsion

Under certain conditions, both "water-in-oil" and "oil-in-water" types of emulsions can be produced by ultrasonic techniques. The traditional emulsification method can only control the properties of the emulsion by adding an emulsifier, and the type of the emulsion cannot be changed simply by mechanical methods. Ultrasonic emulsification equipment makes the emulsification process more convenient and flexible.

Low power consumption

The power consumption of ultrasonic emulsification is smaller, and the power consumption required to manufacture the same volume of emulsion is smaller than that of a high-pressure homogenizer. To manufacture an emulsion with a capacity of 4.55 m3/h and droplets of 1 μm size, such as using ultrasonic emulsification technology, only a driving force of 57 HP can be required at a working pressure of 10.514.1kg/cm2, but a high-pressure homogenizer is 70.3351.6kg. However, a driving force of 4050 HP is required at a working pressure of / cm2, so the use of phacoemulsification technology can reduce a lot of energy consumption.

Improve the efficiency of emulsification

Ultrasonic emulsification can produce emulsions that cannot be produced by ordinary emulsification methods. As the energy density increases, the droplet size decreases. At appropriate energy density levels, phacoemulsification technology can achieve average droplet sizes of less than 1 μm. Ultrasound makes the entire emulsification process faster and produces a higher-purity emulsion.