Quincke, a German experimental physicist, first proposed chemical methods for defoaming. In the 19th century, the colloidal chemist J.P. A Japanese colloidal chemist, hengtaka sasaki, began studying bubbles before world war ii and became an expert in defoaming after the war by publishing numerous articles. S. oss, an American colloidal chemist, studied the defoaming of lubricants during world war ii and published many research reports on defoaming after the war, making outstanding contributions to the mechanism of defoaming agents.In 1952, c.c. coolrie of dow corning company made a large-scale collation of the literature on defoaming agent at that time, and made a comprehensive and systematic research on defoaming technology in paper making, fermentation, boiler and other aspects. In 1954, in the United States, wangnd-ott company first put polyether defoamer into production, which has been rapidly developed. But the extensive application and research began with the development of polyether industry in recent years.In the 1950s, China began to carry out exploratory research on the defoaming problem of fermentation and paper industry. In the early 1960s, China began to systematically study the defoaming of lubricating oil and transmission oil, thus contributing to the development of aircraft, diesel locomotives, ships and cars. Later, the paper, printing and dyeing, fermentation, desulfurization of natural gas, concrete and other aspects of the research.In the late 1960s, China began to study polyether defoaming agents, and since the 1970s, began to produce polyether defoaming agents, which were first used in antibiotic fermentation, and gradually promoted to other fields. The varieties also developed from single glycerol polyether GP to today's GPE, PPE, BAPE and so on. In the 1980s, a variety of defoaming agents are emerging, defoaming technology has been widely used in all walks of life in China. Foam is a dispersion system in which a large number of bubbles are dispersed in a liquid. The dispersed phase is gas and the continuous phase is liquid. When surfactants are added to the system, a layer of surfactant molecules are adsorbed on the surface of the bubble. When the concentration reaches a certain level, a solid film is formed on the bubble wall. The surfactant adsorbs on the gas-liquid interface, causing the surface tension of the liquid to drop, thus increasing the gas-liquid contact surface, so that the bubbles are not easy to merge. The relative density of bubbles is much smaller than that of water, and as the rising bubbles pass through the surface, they attach a layer of surfactant molecules to the surface.Therefore, the bubble film with surfactant adsorbed in the air is different from the bubble film in the solution. It contains two layers of surfactant molecules, forming a bilayer film. The adsorbed surfactant has a protective effect on the liquid film. Defoaming agent is to destroy and inhibit the formation of this film, defoaming agent into the foam of the bi-molecular directional film, the mechanical balance of the directional film to break the bubble. The defoamer must be a liquid that spreads easily on the surface of the solution. The spread of this liquid on the surface of the solution will take away a layer of solution from the adjacent surface, making the liquid film locally thinner, so that the film burst, foam destruction. In general, the faster the defoamer is spread on the surface of the solution, the thinner the liquid film will become, and the critical thickness will be reached quickly. Generally refers to the liquid spreading on the surface, plays the role of defoaming, its surface tension decreases (that is, the surface pressure increases), the occurrence of unbalanced phenomenon. The spreading then occurs locally, taking away the next layer of liquid beneath the surface, thinning the film and damaging the bubble film. Therefore, on the one hand, the reason for defoaming is that it is easy to spread, and the adsorbed defoaming agent molecules replace the foaming agent molecules, forming a film with poor strength. At the same time, part of the solution of the adjacent surface layer was taken away during the spreading process, which thinned the foam liquid film, reduced the stability of the foam and made it easy to be destroyed. An excellent defoaming agent must have both antifoaming and antifoaming effects, that is, it should not only destroy the foam quickly, but also prevent the formation of foam for a long time. It is often found that some defoaming agents lose their effectiveness after a certain amount of time is added to the solution. To prevent foam formation, you need to add some more defoaming agent. The reason for this may be related to whether the critical micelle concentration CMC of foaming agent (surfactant) in solution is exceeded. In more than CMC solution, defoamer (generally organic liquid) may be solubilified, so that the loss of the spread on the surface of the role, defoaming effect is greatly reduced. When the defoaming agent was first added, its spreading speed on the surface was higher than the solubilizing speed, showing better defoaming effect. After a period of time, with the antifoaming agent is gradually solubilized, the antifoaming effect correspondingly weakened.