Defoaming agent selection
The following points should be met when choosing a defoaming agent:
(1) Insoluble or difficult to dissolve in foaming liquid
In order to burst the foam, the defoaming agent should be concentrated and concentrated on the bubble film. In the case of foam breakers, it should be concentrated and concentrated in an instant, and in the case of foam suppressors, it should always be maintained in this state. Therefore, the defoaming agent is in a supersaturated state in the foaming liquid. Only insoluble or poorly soluble defoaming agents can easily reach the supersaturated state. Only when it is insoluble or difficult to dissolve can it easily gather at the gas-liquid interface, be easily concentrated on the bubble membrane, and can it function at a lower concentration. For defoaming agents used in water systems, the molecules of the active ingredients must be strongly hydrophobic and weakly hydrophilic, with an HLB value in the range of 1.5-3 for the best effect.
(2) The surface tension is lower than that of the foaming liquid
Only when the intermolecular force of the defoaming agent is small and the surface tension is lower than that of the foaming liquid can the defoaming agent particles be able to immerse and expand on the bubble film. It is worth noting that the surface tension of the foaming liquid is not the surface tension of the solution, but the surface tension of the foaming solution.
(3) Has a certain degree of affinity with the foaming liquid
Since the defoaming process is actually a competition between foam collapse speed and foam generation speed, the defoaming agent must be quickly dispersed in the foaming liquid in order to quickly play a role in a wider range of the foaming liquid. To make the defoaming agent diffuse quickly, the active ingredient of the defoaming agent must have a certain degree of affinity with the foaming liquid. If the active ingredient of the defoaming agent is too close to the foaming liquid, it will dissolve; if it is too sparse, it will be difficult to disperse. Only when the distance is appropriate can the effect be good.
(4) No chemical reaction with foaming liquid
The defoaming agent reacts with the foaming liquid. On the one hand, the defoaming agent will lose its effect. On the other hand, it may produce harmful substances that affect the growth of microorganisms.
(5) Low volatility and long acting time
First, determine the system that requires the use of defoaming agents, whether it is a water-based system or an oil-based system. For example, in the fermentation industry, oil-based defoaming agents, such as polyether-modified silicone or polyether, must be used. The water-based coating industry requires water-based defoamer and silicone defoamer. Select the defoamer, compare the added amounts, and get the most suitable and economical defoamer product based on the reference price.
