Silicone defoamer not only has good defoaming and defoaming effects, but also has the characteristics of low dosage, good chemical inertness, etc., and can function under harsh conditions.
advantage:
①Wide application: Due to the special chemical structure of silicone oil, it is neither compatible with water or substances with polar groups, nor with hydrocarbons or organic substances containing hydrocarbon groups. Due to the insolubility of silicone oil to various substances, it is widely used and can be used for defoaming in water systems and oil systems.
②Small surface tension: The surface capacity of silicone oil is generally 20-21 dynes/cm, which is smaller than the surface tension of water (72 dynes/cm) and general foaming liquids, and has good defoaming effect.
③Good thermal stability: Take the commonly used dimethicone as an example. It can withstand 150℃ for a long time and more than 300℃ for a short time. Its Si-O bond does not decompose. Ensure
silicone defoamer can be used over a wide temperature range.
④Good chemical stability: Because the Si-O bond is relatively stable, silicone oil has high chemical stability and is difficult to react with other substances. Therefore, as long as the configuration is reasonable, silicone defoaming agents are allowed to be used in systems containing acids, alkalis, and salts.
⑤Physiologically inert: Silicone oil has been proven to be non-toxic to humans or animals, and its half-lethal dose is greater than 34 g/kg. Therefore, silicone defoamer (with appropriate non-toxic emulsifiers, etc.) can be safely used in food, medical, pharmaceutical and cosmetic industries.
⑥ Strong defoaming power: Silicone defoaming agent can not only effectively break the foam that has been generated, but also significantly inhibit foam and prevent the formation of foam. Its usage is very small, as long as one millionth (1ppm) of the weight of the foaming medium is added, it can produce defoaming effect. Its common range is 1 to 100ppm. Not only is the cost low, but it also does not pollute defoaming substances.
shortcoming:
① Difficulty in dispersing polysiloxane: Polysiloxane is difficult to dissolve in water, which hinders its dispersion in the water system. A dispersant must be added. If too much dispersant is added, the emulsion will be stable and the defoaming effect will become worse. It is necessary to Use less emulsifier, so that the defoaming effect is better and the emulsion is stable.
② Silicone is oil-soluble, which reduces its defoaming effect in the oil system.
③High temperature resistance for a long time and poor resistance to strong alkali.
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