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A defoamer manufacturer explains how to choose the right defoamer.
Release Date:
2021-03-23
The aggregated state in which numerous bubbles cluster together, separated from one another by thin films, is called foam. Bubbles and foam are commonly encountered in both daily life and industrial processes: sometimes they are deliberately harnessed—for example, in flotation, fire suppression, dust removal, washing, and the production of foam ceramics and plastics—while at other times they must be eliminated, as in fermentation, coating, papermaking, textile dyeing, the removal of gas from internal organs, boiler water treatment, wastewater treatment, and the manufacture of prisms (or glass).
The aggregated state in which numerous bubbles cluster together, separated from one another by thin films, is called foam. Bubbles and foam are commonly encountered in both daily life and industrial processes: sometimes they are deliberately harnessed—for example, in flotation, fire suppression, dust removal, washing, and the production of foam ceramics and plastics—while at other times they must be eliminated, as in fermentation, coating, papermaking, textile dyeing, the removal of gas from internal organs, boiler water treatment, wastewater treatment, and the manufacture of prisms (or glass).
As defoamers, they all exhibit strong defoaming performance, physiological inertness, heat and oxidation resistance, corrosion resistance, gas solubility, gas permeability, easy diffusion and penetration, poor solubility in the defoaming system without causing physicochemical effects, low dosage requirements, and high efficiency. The “foam‑inhibition” and “foam‑breaking” processes of a defoamer proceed as follows: upon addition to the system, its molecules randomly distribute across the liquid surface, inhibiting the formation of an elastic film and thereby halting foam generation. When significant foam has already formed, introducing the defoamer causes its molecules to rapidly spread over the foam surface, forming an extremely thin bilayer that further diffuses and penetrates, invading the foam structure layer by layer and ultimately replacing the original thin bubble wall.
About Defoamer The choice must meet the following criteria:
1. Insoluble or poorly soluble in the foaming solution
To break bubbles, defoamers should concentrate and accumulate at the bubble film. For bubble‑breaking agents, this concentration must occur instantaneously; for foam‑inhibiting agents, such a state should be maintained continuously. Consequently, defoamers exist in a supersaturated condition within the foaming liquid, and they readily reach supersaturation only when they are essentially insoluble or poorly soluble. Only when insoluble or poorly soluble do they tend to adsorb at the gas–liquid interface, concentrate on the bubble film, and exert their effect even at low concentrations. For aqueous systems, the active ingredient should exhibit strong hydrophobicity and weak hydrophilicity, with an HLB value in the range of 1.5–3, to ensure optimal performance.
2. The surface tension is lower than that of the foaming liquid.
Only when the intermolecular forces of the defoamer are weak and its surface tension is lower than that of the foaming liquid can the defoamer particles penetrate and spread across the bubble film. It is worth noting that the surface tension of the foaming liquid is not the surface tension of the solution itself, but rather the surface tension of the foam‑stabilizing solution.
3. Exhibits a certain degree of affinity with the foaming liquid.
Since the defoaming process essentially involves a competition between the rate of foam collapse and the rate of foam formation, a defoamer must be able to disperse rapidly in the foaming liquid, thereby exerting its effect over a broad area. To ensure rapid spreading, the active ingredient of the defoamer should exhibit a certain degree of affinity with the foaming liquid. If the active ingredient is too compatible with the liquid, it will dissolve; if it is too incompatible, it will be difficult to disperse. Only when compatibility is just right can the defoamer perform effectively.
4. Does not undergo a chemical reaction with the foaming agent.
The defoamer reacts with the foaming liquid; on the one hand, it loses its effectiveness, and on the other hand, it may generate harmful substances that inhibit microbial growth.
5. Low volatility and long-lasting efficacy.
To determine whether a defoamer is required, first identify whether the system is water-based or oil-based. For example, in the fermentation industry, oil‑based defoamers—such as polyether‑modified silicones or polyether‑type defoamers—are appropriate, whereas the water‑based coatings industry calls for water‑soluble defoamers, typically silicone‑based ones.
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