How is the defoamer deactivated？

Silicone oil defoamers generally include several different silicone oils, some of which are relatively easy to separate from the oil phase and dissolve into the micelles of surfactant molecules, so that the composition of the oil phase of the defoamer dispersion is changed, thereby reducing the activity of the defoamer. Generally speaking, silicone oil with large molecular weight is insoluble in surfactant solvents, but commercial silicone oil often contains small molecular silicone oil, which is easily solubilized by surfactant molecules, resulting in changes in the composition of defoaming agents and weakened defoaming ability.


The formation of a silicone oil layer on the foam film is a prerequisite for defoaming, but during the defoaming process, the silicone oil layer formed by the defoaming agent dispersion on the foam film will be slowly emulsified and then enter the solution, so that the defoaming performance is reduced. It can be said that the process from defoaming to deactivation is the process of spreading the silicone oil layer on the foam film-oil bridge formation/emulsification. When the silicone oil layer begins to enter the surface of the foam film, the spreading rate will increase, but with the defoaming process, the silicone oil will continue to emulsify, the spreading rate will decrease and the formation of the oil bridge will be reduced, when there is no spreading silicone oil layer on the foam film, the defoamer is deactivated.


The hydrophobic solid particles as the active ingredient in the silicone oil defoamer system slowly come out of the defoamer dispersion and into solution when in contact with the surfactant solution for a long time. These defoamer dispersions that lose silicon particles cannot enter the surface of the foam film because of excessive insertion resistance, while some silicone oil molecules that have entered the foam film will be adsorbed to the surface of solid particles and then enter the solution, resulting in a decrease in the hydrophobicity of the defoamer dispersion on the foam film, an increase in hydrophilicity, and finally a loss of defoaming performance.