The first kind of defoamer is mainly composed of various organic substances, such as fatty acids, mineral oils, fatty amides, low alcohols, etc. Most of the defoamers are natural substances, which cause little environmental pollution and low price. Because the defoaming property is relatively weak, a large amount of foam can not meet the requirements of production.           
The second type is polyether defoamer CNH (2n + 1) O (EO) a (PO) BH, polyoxyethylene segment (EO) is hydrophilic, and polyoxypropylene segment (PO) is lipophilic. The antifoaming agent has good antifoaming performance, no toxicity, no stimulation, and good dispersibility. In practical production, the relative molecular weight of polyether and the ratio of EO and PO in polyether segments can be adjusted to meet the needs of various production fields. At present, polyether Defoamers in the market mainly include straight chain polyether, ether amine, fatty alcohol polyether, fatty acid polyoxyethylene ether, etc.           
The third type is organosilicon defoamer, which has better defoaming performance than the former two. Generally, the silicone oil with large molecular weight is insoluble in surfactant solution, while the silicone oil with small molecular weight is easily solubilized by surfactant, which changes the composition of defoamer and weakens its defoamer performance. The antifoaming agent of silicone oil is insoluble in water and mineral oil, so its antifoaming ability is strong and its antifoaming effect is greatly enhanced. Because Si-O bond and Si-C bond are relatively stable, they are allowed to be used in systems containing a small amount of acid, alkali and salt. Most of the commonly used organosilicon Defoamers in industrial production are a kind of secondary processing products of silicone oil made by adding dispersants to silicone oil, which are all liquid mixtures. The mixture is mainly divided into five types: silicon paste type, silicone oil type, emulsion type, solution type and solid type from appearance and fluidity.           
The fourth type of defoamer is polyether modified silicone oil defoamer. On the basis of previous generations of defoamers, the advantages of polyether and silicone are integrated, and polyether chain segment is introduced into silicone oil chain segment, which has stronger defoaming and antifoaming properties. Polyether modified silicone oil is a new type of special silicone surfactant, which is formed by the addition reaction of polyether containing double bond and low hydrogen silicone oil. It is a kind of silicone non-ionic surfactant with unique performance. It not only retains the high and low temperature resistance, weather resistance, demoulding, hydrophobicity and physiological inertia of silicone oil, but also has non irritant and high surface activity of polyether Polyether modified silicone oil can be dissolved in water and soluble in oil phase, so it can be used as silicone surfactant. Polyether segments can also be used as emulsifiers to keep the properties of emulsion stable and have good dispersibility. Therefore, polyether modified silicone oil has a lasting defoaming effect in water system. Because polyether modified silicone oil has good heat resistance, shear resistance, acid and alkali resistance, non-toxic, tasteless and stable storage, it is widely used, especially when silicone oil defoamer is difficult to solve.