What are the types of silicone defoamers
There are a wide variety of domestic and foreign defoamers with varying properties. Currently, there are generally three types of defoamers commonly used, namely polyether type, silicone oil type, and silicone ether mixed type.
3.1 Polyether type defoamers generally have high spreading coefficients for organic compounds such as ethers, hydrocarbons, alcohols, and phosphate esters, resulting in strong defoaming effect but poor foam inhibition effect. The polyether prepared by ring opening polymerization of ethylene oxide and propylene oxide is an excellent water-soluble non ionic surfactant, with a typical structure of CnH2n+1O (EO) a (PO) bH. The polyepoxyethane segment in the molecule is a hydrophilic group, while the polyepoxypropane segment is a hydrophobic group. Polyether is soluble in water when the amount of ethylene oxide exceeds 25%. The indicator for characterizing the water solubility of polyethers is cloud point. Adjusting the ratio of ethylene oxide and propylene oxide can produce surfactants with different hydrophilic and lipophilic equilibrium values (HLB), achieving the desired surface activity. By adjusting the EO/PO ratio and relative molecular weight, improving its water solubility and oil solubility, the surface tension of the foaming solution can be greatly reduced, and it has good defoaming and foam inhibition capabilities. The biggest advantage of polyether defoamer is its strong foam inhibiting ability, so it is the leading defoamer currently used in the fermentation industry. However, it has a fatal disadvantage that the foam breaking rate is low. Once a large number of foam is generated, it cannot be effectively extinguished at once, but needs a certain amount of new defoamer to slowly solve the problem.
3.2 Silicone based defoamers: Pure organic silicon, such as dimethyl silicone oil, has no defoaming effect. But after emulsification, the surface tension rapidly decreases, and a very small amount can achieve strong foam breaking and inhibiting effects, becoming an important defoamer component. Silicone oil type defoamers generally have high defoaming efficiency, and the key to their use is the emulsification of silicone oil. If the emulsification is not complete, it will break the emulsion during use, affecting its effectiveness. The commonly used organosilicon defoamers are formulated with silicone oil as the basic component, combined with suitable solvents, emulsifiers, or inorganic fillers. Organosilicon, as an excellent defoamer, has strong defoaming power and is particularly valuable for its combination of chemical stability, physiological inertness, and good high and low temperature performance, making it widely used. Due to the lipophilicity of silicone oil itself, it has a satisfactory defoaming effect on oil soluble solutions. Organosilicon defoamers are low toxicity, antioxidant, and strong defoamer breaking agents. However, their foam inhibiting ability is poor, their consumption is large, their effect on slightly acidic fermentation is poor, and they also have a certain inhibitory effect on mycelial development. Therefore, its application in the fermentation industry is subject to certain limitations; In the textile printing and dyeing industry, especially when using light colored fabrics, silicon spots are difficult to clean and are once again restricted.