First, the principle of defoamer






01 Reduce the local surface tension of foam






When a high alcohol or vegetable oil is spread on the foam, it will significantly reduce the surface tension there when dissolved into the foam solution. Because these substances are generally less soluble to water, the reduction in surface tension is limited to local areas of the foam, while the surface tension around the foam hardly changes. The portion with reduced surface tension pulls strongly around, extends, and finally breaks.






02 Damage membrane elasticity






After the defoamer is added to the foam system, it diffuses to the gas-liquid interface, which makes it difficult for the surfactant with foam stabilization function to restore the elasticity of the film.






03 Promote liquid membrane drainage






The defoamer can promote the liquid film to drain, resulting in the bubble bursting. The rate of foam drain can reflect the stability of the foam. The addition of a substance that accelerates the foam drain can also play a role in defoaming.






04 Add hydrophobic solid particles






The hydrophobic solid particles on the surface of the bubble will attract the hydrophobic end of the surfactant, so that the hydrophobic particles produce hydrophilicity and enter the water phase, thus playing the role of defoamization.






05 solubilizing foaming surfactant






Some low molecular substances that can be fully mixed with the solution can make the bubble surfactant solubilize and reduce its effective concentration. Low molecular substances with this effect, such as octanol, ethanol, propanol and other alcohols, can not only reduce the surfactant concentration of the surface layer, but also dissolve into the surfactant adsorption layer, reducing the tightness of the surfactant molecules, thereby weakening the stability of the foam.






06 Electrolyte disintegrates the surfactant double electric layer






With the interaction of the double electric layer of the surfactant in the foam, the stable foaming liquid is produced. The addition of ordinary electrolyte can disintegrate the double electric layer of the surfactant and play the role of defoaming.






Second, the selection of defoamer






01 Insoluble or insoluble in foaming solution






In order to burst the foam, the defoamer should be concentrated and concentrated on the foam. For the case of defoaming agent, it should be concentrated and concentrated in an instant, and for the case of defoaming agent, it should always be maintained in this state. Therefore, the defoamer is supersaturated in the foaming solution, and only insoluble or insoluble is easy to achieve supersaturation. Insoluble or insoluble, it is easy to gather at the gas-liquid interface, it is easy to concentrate on the bubble film, and it can play a role at a lower concentration. For the defoamer used in water system, the molecules of the active ingredients must be strong hydrophobic and weak hydrophilic, and the HLB value is 1.5~3, the effect is the best.






02 Surface tension is lower than the foaming solution






Only when the intermolecular force of the defoamer is small and the surface tension is lower than that of the foaming solution, the defoamer particles can be immersed and expanded on the foam film. It is worth noting that the surface tension of the foaming solution is not the surface tension of the solution, but the surface tension of the foaming solution.






03 Has a certain degree of affinity with foaming liquid






Since the defoaming process is actually a competition between the speed of foam collapse and the speed of foam formation, the defoaming agent needs to be able to disperse quickly in the foaming solution in order to play a rapid and extensive role in the foaming solution. In order to make the defoamer diffuse quickly, the active ingredients of the defoamer need to have a certain degree of affinity with the foaming solution. If the active ingredient of defoamer is too close to the foaming solution, it will dissolve. Too sparse will be difficult to disperse. The effectiveness is better when the affinity is appropriate.






04 No chemical reaction with foaming solution






The defoamer reacts with the foaming solution, on the one hand, the defoamer will lose its effect, on the other hand, harmful substances may be produced, affecting the growth of microorganisms.






05 Small volatility, long action time






First of all, determine the system that needs to use defoamer, water-based system or oil-based system. If the fermentation industry, it is necessary to use oil-based defoamer, such as polyether modified silicon or polyethers. Water-based coating industry must use water-based defoamer, silicone defoamer. Select the defoamer, compare the amount of addition, and then refer to the price, we can get the most applicable and economical defoamer products.






Third, the amount of defoamer






There are many types of defoamer, and the amount of addition required for different types of defoamer is different.






Alcohol defoamer


When alcohol defoamer is used, the dosage is generally 0.01%~0.10%.


Oil defoamer


The addition amount of oil defoamer is 0.05%~2%, and the addition amount of fatty acid ester defoamer is 0.002%~0.2%.


Amide defoamer


The effect of amide defoamer is better, and the addition amount is generally 0.002% to 0.005%.


Phosphoic acid defoamer


Phosphoic acid defoamer is most commonly used in fibers and lubricants, with the addition amount of 0.025% to 0.25%.


Amine defoamer


Amine defoamer is mainly used in fiber processing, and the addition amount is 0.02% to 2%.


Ether defoamer


Amine defoamer is mainly used in fiber processing, and the addition amount is 0.02% to 2%.






The principle of defoaming agent is to use local surface tension, destroy membrane elasticity, promote liquid membrane drainage, add hydrophobic solid particles and other processes. The selection of defoamer should conform to the corresponding characteristics. Control of usage is also important.