Why Is Ultrasonic Technology Superior For Producing Stable Silicone Emulsions？

I. Core Working Principle of Ultrasonic Silicone Oil Emulsification

The core driving force of ultrasonic emulsification is the liquid cavitation effect. The device uses a 20–40kHz high-frequency vibrating titanium alloy ultrasonic probe to transmit acoustic energy to the water-silicone oil mixture.

Microbubble formation: Alternating sound pressure causes a large number of micron-sized cavitation microbubbles to form inside the liquid;

Bubble collapse: After rapid expansion, microbubbles collapse violently and instantaneously, generating localized high temperatures of thousands of K and high pressures of hundreds of MPa, accompanied by shock waves and high-speed microjets;

Ultrafine droplet fragmentation: Shock waves and strong shear forces tear apart large silicone oil droplets, breaking down the continuous oil phase into uniformly dispersed micro-phases;

Interface stability: Ultrasonic disturbance promotes the rapid distribution of emulsifiers on the surface of silicone oil droplets, forming a dense protective film and inhibiting droplet aggregation.

The average particle size of ultrasonically emulsified silicone oil emulsions can reach 0.1–1 μm, with a particle size distribution index (PDI) < 0.3, which is far superior to the 5–20 μm droplet size produced by high-speed stirring. It is less prone to stratification, oil floating, and sedimentation during centrifugation and long-term storage. The entire process does not require prolonged heating, avoiding the high-temperature yellowing and performance degradation problems associated with amino silicone oils and modified polyether silicone oils.

II. Core Advantages of Ultrasonic Emulsification in the Preparation of Silicone Oil Emulsions

1. Improve emulsion stability and reduce scrap rate.

Traditional mechanical shearing relies solely on blade friction to break up silicone oil, resulting in droplet sizes that vary widely, with large particles easily floating and separating. Ultrasonic cavitation, on the other hand, provides uniform action across the entire surface, producing silicone oil droplets of consistent size and height. Centrifugation at 3000 r/min for 30 minutes yields no demulsification, and sealed storage at room temperature for over 6 months shows no floating oil, making it suitable for long-distance transportation and extended storage.

2. The amount of emulsifier used is significantly reduced, improving the product's skin-friendly/hydrophilic properties.

In the textile and daily chemical industries, excessive emulsifiers in silicone oil emulsions often lead to water repellency in fabrics, a slippery feel in washing and conditioning products, and increased irritation. The powerful interfacial action of ultrasound can reduce the interfacial tension between oil and water, reducing the amount of emulsifier added by 20%–40% compared to traditional processes. This not only controls production costs but also produces low-irritation, highly hydrophilic amino silicone oil emulsions and hair conditioning silicone oil emulsions.

3. Low-temperature emulsification protects the functionality of modified silicone oil.

Modified organosilicones such as amino silicone oil, polyether-modified silicone oil, and aryl silicone oil are prone to oxidation and yellowing at high temperatures, and lose their soft and hydrophilic properties. Ultrasonic emulsification allows for controlled temperature rise throughout the process, eliminating the need for prolonged heating and fully preserving the original softness, antistatic properties, and spreading characteristics of silicone oil. It is suitable for the production of high-end laundry care and hydrophilic textile softeners.

4. Suitable for emulsification of high viscosity, high solids content silicone oils

For high-viscosity dimethyl silicone oil and amino silicone oil with a viscosity of 1000–100000cs, high-speed stirring can easily lead to agglomeration and localized unemulsified oil clumps. Ultrasonic microjets can penetrate the high-viscosity oil phase and stably prepare high-concentration silicone oil emulsions with a solid content of 20%–50%, reducing transportation and dilution costs and meeting the high solids requirements of coating defoaming and industrial demolding.

5. Energy-efficient, high-performance, and easy to maintain

Ultrasonic emulsification consumes 25%–40% less energy than high-pressure homogenization for the same production capacity; it has no easily worn parts such as high-pressure valves and grinding discs, the titanium alloy probe is corrosion resistant, the long-term continuous operation has low maintenance costs, and it can be flexibly switched between intermittent laboratory models and continuous online industrial models.

6. Flexible process, adaptable to microcapsule and nano silicone oil special systems

It can prepare nano-silicone oil microemulsions and slow-release silicone oil microcapsules in one step, with droplets as small as hundreds of nanometers. It can be used in high-end skin care essences, long-lasting waterproof coatings, and pesticide spreading aids. It is a fine formulation process that is difficult to achieve with traditional emulsification equipment.

III. Typical Process Flow of Ultrasonic Silicone Oil Emulsification

Premix: Silicone oil, compound emulsifier, and deionized water are added to a mixing tank according to the formula ratio and premixed at low speed to form a coarse oil-water mixture;

Ultrasonic homogenization: The mixture is fed into an ultrasonic homogenizer and continuously circulated at 20kHz for 3–10 minutes, with real-time monitoring of particle size until it meets the standard.

pH adjustment and heat preservation: Adjust the pH to neutral (6.0–8.0) with a small amount of citric acid/triethanolamine, and let it stand at low temperature to defoam;

Filtration and Packaging: Use a 100–200 mesh filter to remove trace amounts of unemulsified oil clumps, and then fill the container after testing for particle size, centrifugal stability, and solid content.

Laboratory pilot tests used a benchtop intermittent ultrasonic homogenizer (processing capacity 0.5–50L), while pilot-scale and mass production used a pipeline continuous ultrasonic emulsifier unit, which can be connected to an automated production line for online real-time sampling and monitoring of emulsion particle size.