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Factors affecting foam stability

wallpapers Industry 2020-04-08

Foam is an unstable system that can cause structural changes over time. The stability of the foam depends on the ease of defoaming. Once the foam bursts, the surface energy of the system will decrease. For foams made from blown formulations, the influencing factors are about the same.

1. Surface tension

The surface tension of pure water is very high, which makes foam molding difficult. After adding a surfactant to the water, the surface tension of the aqueous solution decreases, and foam molding is generally relatively safe and stable. Because of the surface energy of the foam increases as the surface area of ​​the liquid increases. When the bubble bursts, the strength of the system will also decrease. Therefore, if the surface tension of the liquid is low, the surface energy of the foam is relatively small. When the foam bursts, the surface energy also decreases. But the surface tension of the liquid is not a determinant of foam stability. The main factor determining foam stability is the strength of the liquid film. Only when a specific strength film is formed on the liquid surface, low surface tension can promote the stability of the foam.

2. Surface viscosity

The strength of the liquid film determines the safety of the foam. The key characteristic of the power of the liquid film is the surface viscosity. The surface viscosity depends on the tightness of the arrangement of molecules in the film. Measuring surface viscosity can identify different states of single-molecule theater, which is an important factor for foam stability.

The higher the surface viscosity, the greater the thickness of the liquid film, the higher the surface adsorption strength, the lower the liquid film rate, and the longer the life of the foam.

However, if the surface viscosity is too high or too low, it is impossible to form a stable foam. Only with the proper thickness can a more stable foam be formed.

3. Liquid viscosity

The width in the liquid is also one of the factors that affect the stability of the foam. The liquid has a high viscosity, which produces a thick liquid film, which increases the strength of the liquid film. Foam liquid membranes are often not easily broken, and the liquid on the surface adsorption layer does not flow naturally.

4. Liquid film elasticity

Foam is a quite complex thermodynamic system, and there are many factors that affect the stability of the foam. The stability of foam is mainly determined by the speed of liquid discharge and the strength of the liquid film.

Liquid membrane elasticity refers to the repair effect of surface tension. When the foam is affected or disturbed by external forces, the liquid film will locally thin, thereby increasing the area of ​​the liquid film. Increasing the surface area requires more work. In order to make the membrane have better elasticity, the adsorption capacity of the foam stabilizer is often higher.

In addition, the foaming agent concentration, temperature, and parameters of the foam generator are all factors that affect the stability of the foam.


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