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The physical and chemical properties of high quality defoamers must meet the requirements of the use system. Generally speaking, the following requirements must be considered when choosing a defoamer:

(1) Strong defoaming ability. It can effectively eliminate foam when using a very small amount;

(2) It has a lower surface tension of the defoaming system, that is, the surface tension of the defoaming agent itself is lower;

(3) After the defoamer is added, it will not affect the basic performance of the defoamed system;

(4) It is insoluble in the defoaming system, and it is not easy to be solubilized by the surfactants in the system. If it is solubilized, it will lose its defoaming ability and lose its anti-foaming ability;

(5) The surface balance is better;

(6) It does not react with the defoamed medium, nor will it be decomposed and degraded, and has good chemical stability;

(7) It has good diffusibility and permeability, that is, it has a positive diffusion coefficient in the foam medium, and has
Ability to spread quickly on the foam surface;

(8) The heat resistance of defoamer is better, and it will not lose its effectiveness at high temperature;

(9) It has good gas solubility and permeability, so that the gas is not easy to gather and disappear from the foam, and the foam is easy to eliminate;

(10) It has high physiological activity and high safety in the defoaming system. The defoamer itself is preferably non-toxic, at least a low-toxic substance;

(11) It has low COD, BOD and TOD values;

(12) It has good storage stability;

(13) It has a long-term defoaming effect, and some defoamers can quickly defoam, but they will fail after a long time;

(14) Low cost;

(15) Does not increase the surface viscosity of the surfactant aqueous solution.

It is difficult to meet the above requirements of defoamers at the same time, and can only meet the requirements of the defoamed system in terms of main performance. Each defoamer can only be effective for a certain system or several systems. It is impossible to expect that one defoamer can achieve the purpose of defoaming. In addition, a variety of different defoamers can be selected for the same foam system. Because of this, there are many types of defoamers, at least 500 or more. The user has to conduct tests and choose the most effective and economical defoamer. Now the research on defoamers has aroused the interest of the majority of researchers. More than one hundred articles are published every year, and new varieties and new patents are emerging in endlessly.