Additius de formigó lleuger | Agents espumants d'alt rendiment per al formigó cel·lular
What is the foam stability of cellular concrete foaming agent?
L'estabilitat de l'escuma de l'agent d'escuma de formigó cel·lular es refereix al rendiment que l'escuma pot existir durant molt de temps sense esclatar.. Com més temps existeix la bombolla, millor és l'estabilitat i menys probabilitats d'esclatar. The destruction process of foam is mainly the process of the liquid film separating the gas from thick to thin until it bursts. The main factors affecting the foam stability of cement foaming agent are as follows:
1. Bubble film thickness
If the thickness of the bubble liquid film produced by the cellular concrete foaming agent is too small, the mechanical strength is low, the resistance to external force is poor, and it is easy to rupture; the bubble liquid film is too thick, and the water between the bubbles is too high, resulting in excessive foam bleeding, and the liquid film is too thick It will speed up the discharge and easily cause the bubble to break. Per tant, the thickness of the bubble film layer should be kept within a certain range.
2. Viscositat
The strength of the bubble liquid film produced by the cellular concrete foaming agent is a key factor in determining the stability of the foam. The strength of the liquid film depends on the firmness of the surface adsorption film. Its firmness is related to the surface viscosity. Com més gran sigui la viscositat superficial, the formation The longer the bubble life. D'altra banda, the higher the viscosity of the liquid itself, the slower the liquid overflows from the liquid film, thereby enhancing foam stability.
3. Liquid surface tension
The lower liquid surface tension is good for foam formation, but it cannot guarantee foam stability. The protein foaming agent has higher liquid surface tension, although the foaming ratio is lower, but the foam produced has higher stability.
4. Surface charge
When the two surfaces of the bubble liquid film have the same kind of electric charge, they repel each other, which can prevent the liquid film from being squeezed and thinned to break.
5. Foam self-healing ability
When the foam liquid film is subjected to external force, the local thickness of the liquid film becomes thinner, which is prone to bubble breaking. When the foaming agent is adsorbed on the surface of the liquid film, it can resist surface expansion and contraction, so that the thickness of the liquid film can be restored and the strength Recovery, self-repair of surface tension.
6. The molecular structure of surfactants
The hydrophobic chain of the surfactant should be of moderate chain length to ensure that the adsorption film formed on the surface of the liquid film has a high viscosity; the hydrophilic group of the surfactant has a strong hydration capacity, which can make the foam liquid film high flow The degree of free water becomes bound water with poor fluidity, thereby increasing the viscosity of the liquid film.
5. Foam self-healing ability
When the foam liquid film is subjected to external force, the local thickness of the liquid film becomes thinner, which is prone to bubble breaking. When the foaming agent is adsorbed on the surface of the liquid film, it can resist surface expansion and contraction, so that the thickness of the liquid film can be restored and the strength Recovery, self-repair of surface tension.
6. The molecular structure of surfactants
The hydrophobic chain of the surfactant should be of moderate chain length to ensure that the adsorption film formed on the surface of the liquid film has a high viscosity; the hydrophilic group of the surfactant has a strong hydration capacity, which can make the foam liquid film high flow The degree of free water becomes bound water with poor fluidity, thereby increasing the viscosity of the liquid film.
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