I. Analysis of the Main Components in the Compound Polyether-Silicone Defoamer

Polyether-modified silicone oil exhibits strong emulsifying power, capable of both emulsifying silicone oils and self‑emulsifying, resulting in a highly stable emulsion system. Benefiting from the low surface tension of polysiloxanes and the easy dispersibility of polyethers, it facilitates the uniform dispersion and spreading of defoamers. Above its cloud point, it demonstrates defoaming activity; below the cloud point, it remains dispersed within the foaming liquid, ensuring long‑lasting defoaming performance. Polyether‑silicone oil also boasts excellent properties, including superior resistance to high and low temperatures, chemical stability against acids and bases, aging resistance, electrical insulation, softness, safety and environmental friendliness, storage stability, and ease of use, making it a high‑performance defoamer with broad application prospects.

II. Effect of Polyether-Silicone Oil Dosage on the Performance of Defoamers

Polyether silicone oil itself possesses both defoaming and foam‑suppressing properties and can also synergize with methyl silicone oil or modified fumed silica. Studies have shown that, within a certain dosage range, as the amount of polyether silicone oil added increases, the defoaming time shortens while the foam‑suppressing duration is extended. This is attributable to the self‑emulsifying nature of polyether silicone oil, which enhances the stability of the emulsion and its dispersibility in water, enabling synergistic interactions among the components and thereby significantly improving the defoaming performance of the defoamer.

3. Effect of Methyl Silicone Oil Viscosity and Dosage on the Performance of Defoamers

Dimethyl silicone oil is also a commonly used primary ingredient in defoamers. The general rule regarding its dosage and applicable viscosity is as follows: the lower the viscosity of the foaming liquid, the higher the viscosity of the silicone oil that should be selected; however, high‑viscosity methyl silicone oils have low solubility and provide long‑lasting foam suppression but are difficult to emulsify. Conversely, the higher the viscosity of the foaming liquid, the lower the viscosity of the silicone oil that should be chosen—such oils disperse more readily in the liquid to exert a defoaming effect, yet their greater solubility results in shorter foam‑suppression durations. The concentration of methyl silicone oil in the emulsion should also be moderate: too low a dosage yields poor defoaming performance, while excessive use makes emulsification challenging. Defoamers with low solubility can suppress foam formation over an extended period, continuously disrupting the foam system.

IV. Influence of Silica Selection and Dosage on the Performance of Defoamers

Fumed silica (precipitated silica) has a large specific surface area, low density, and excellent dispersibility. Without hydrophobic treatment, it exhibits hydrophilicity, making it difficult to wet and disperse in organic phases. After hydrophobic modification, the surface hydroxyl content decreases, the tendency for aggregation is reduced, and the surface free energy declines, transforming its character from hydrophilic to hydrophobic and thereby improving its wettability and dispersibility in organic media. Fumed silica is commonly used to enhance the dispersibility of silicone oils in foaming systems and to increase the stability of emulsions. In defoamers, the optimal dosage of fumed silica is approximately 1.3%.

5. Influence of Emulsifier Selection and Dosage on the Performance of Defoamers

To form a stable emulsion, it is essential to select an appropriate emulsifying system. First, the HLB value of the emulsifier should be close to that of the silicone oil (approximately 8–11). Second, the emulsifier should exhibit low foaming properties. Additionally, consider the affinity between the emulsified system and the hydrophobic moiety of the emulsifier; the closer their structural compatibility, the better the emulsification performance. Span and Tween series emulsifiers, with chemical structures similar to those of silicone oils, are widely used for emulsifying silicone oils. The dosage of the emulsifier also requires careful consideration: excessive amounts improve stability but can result in an overly viscous emulsion with diminished defoaming efficiency, whereas insufficient dosing leads to instability and easy phase separation. When selecting emulsifiers, it is common practice to formulate blends using several emulsifiers with slightly different HLB values, as this approach generally yields superior results compared to using a single emulsifier.

6. Research Progress on Polyether-Modified Silicone Defoamers

Xie Wenfeng and others synthesized a stable emulsion‑type silicone defoamer, SX P‑3, using polydimethylsiloxane, modified silicone oil, and precipitated silica as the main components. This product exhibits rapid spreading, uniform dispersion, non‑volatility, high chemical stability, resistance to high temperatures and to both acids and bases, a broad application range, low dosage requirements, and strong efficacy. Li Adan prepared modified silicone oil by reacting polydimethylsiloxane with polyether (glycerol polyoxyethylene‑polyoxypropylene ether). Cai Zhenyun’s research group conducted systematic studies on grafting modifications of polyethers with varying structures and molecular weights, as well as silicon oils with different viscosities and hydrogen contents, using propylene glycol polyether; they obtained various polyether‑silicone oil structures that demonstrate excellent defoaming and foam‑suppressing performance, and further investigated their blending and properties. Wu Fei and Cao Zhiping invented an efficient, safe, and cost‑effective silicone defoamer for waterborne flexographic inks and waterborne coatings, along with its formulation process. An Qiufeng and colleagues, building on the synthesis of amino‑modified silicone oil, carried out preliminary investigations into the addition reaction between polyether and end‑capped silicone oil. Zhang Baoyin and others used polyether 5010 as the primary raw material and, under the catalysis of the GR‑03 specialized emulsifier, developed a composite polyether‑silicone oil defoamer whose defoaming performance is nearly twice that of conventional silicone emulsions.

With the continuous discovery of new, highly active antifoaming ingredients and the deepening research into the synergistic effects of compounded formulations, antifoaming agents are evolving toward greater efficiency, longer-lasting performance, and multifunctional integration—leveraging the strengths of each while mitigating their limitations. The development of novel, high‑efficiency, multifunctional silicone‑polyether antifoams that are widely applicable, require only small dosages, and can enhance product quality and equipment utilization has become the current direction of antifoam technology. Meanwhile, the ongoing exploration and emergence of new application areas offer promising market prospects for such advanced, multifunctional silicone‑polyether antifoams. For example, in the food industry, they are employed to control foam during concentration, fermentation, and distillation processes; in medicine, they are commonly used preoperatively and prior to endoscopic or gastroscopic examinations to eliminate gas from hollow organs or the stomach; and in the production of personal protective products, polyether‑modified silicones—possessing self‑emulsifying properties, surface activity, and physiological inertness—can be formulated into colorless, odorless, non‑irritating personal care items that do not impede the skin’s natural respiration, as well as hair‑care products that impart shine, provide antistatic benefits, and exhibit antibacterial activity.