There are three main types of silicone defoamer, namely, polyether defoamer, silicone oil defoamer, and silicone ether mixed defoamer.
1, Polyether type defoamer
General organic compounds are relatively large spreading coefficient, such as ethers, long-chain hydrocarbons, alcohols and phosphate esters, so their bubble-breaking effect are relatively strong, but the role of foam inhibition are generally very poor. The polyether obtained by ring-opening polymerization of ethylene oxide and propylene oxide is an excellent water-soluble nonionic surfactant, and the typical structure of this surfactant is: CnH2n+1O(EO)a(PO)bH, in which one segment of the polyethylene oxide chain is a hydrophilic group, while the segment of the propylene oxide chain is a hydrophobic group.
The biggest advantage of polyether type defoamer is that the ability to inhibit foam is stronger than the general surfactant, so it is more commonly used as a leading defoamer, the disadvantage is also relatively obvious, that is, the rate of breaking foam is relatively low.
2, silicone oil type defoamer
Silicone alone does not have the role of defoaming, such as dimethyl silicone oil. But the silicone emulsification, their surface tension is reduced relatively quickly, the use of a small amount can achieve a strong bubble-breaking and foam inhibition effect, is a relatively important component of the defoamer. Silicone oil type defoamer defoaming efficiency is generally high, the key factor is the emulsification of silicone oil, if the emulsification is not complete, the use of the emulsion will be broken, affecting the use of the effect. More commonly used silicone defoamer are silicone oil as the base component, and then with the appropriate solvent, emulsifier or inorganic filler to prepare the. In addition to the characteristics of silicone antifoaming ability is relatively strong, but also has chemical stability, inertness and temperature adaptability, all the more widely used. Because the silicone oil itself is oleophilic, so the defoaming of oil-soluble solutions has a satisfactory effect.
Silicone defoamer, is a relatively low toxicity, wax emulsion michelman antioxidant and foam-breaking ability are relatively strong defoamer, but the disadvantage is that the foam inhibition ability is relatively poor, the consumption is relatively large.
3, polyether-modified silicone defoamer
Polyether-modified silicone defoamer is a polyether-siloxane copolymer (referred to as silicone ether copolymer) synthesized by adding polyether chain segments to siloxane molecules. Polyether modified silicone defoamer is a combination of the advantages of polyether type defoamer and silicone oil type defoamer, its main components are dimethyl silicone oil and some emulsifiers and stabilizers. This type of defoamer is characterized by low surface tension, rapid defoaming, long foam inhibition time, low cost, low dosage, wide range of applications and a series of characteristics.
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