Defoamers are used to prevent the formation of bubbles in lubricating oil. The principle of action is to change the surface tension of foam to make small bubbles gather into large bubbles, so as to break the bubbles and achieve defoaming.
Defoaming mechanism of defoamer: foam is often accompanied by people's life and production, and sometimes it needs to be used, such as flotation, fire fighting, dust removal, washing, manufacturing foam ceramics and plastics, etc; Sometimes it is necessary to eliminate it, such as fermentation, coating, papermaking, printing and dyeing, elimination of internal organ swelling, boiler water use, wastewater treatment, and manufacturing of prisms (or glass).
1.The surface tension of foam part decreases, leading to the rupture of foam.
The origin of this mechanism is to disperse higher alcohols or vegetable oils onto foam, which will significantly reduce the surface tension when dissolved in foam. Because these substances are generally insoluble in water, the reduction of surface tension is limited to the part of foam, and the surface tension around foam is almost unchanged. A portion of the surface tension that decreases is strongly stretched, extended, and ultimately ruptured.
2. Disrupts the elasticity of the membrane, causing bubbles to burst.
When defoamer is added to the foam system, it will diffuse to the gas-liquid interface, making the foam stabilizing effect of surfactant ineffective and difficult to restore the elasticity of the film.
3.Promote liquid film drainage
Defoamers can promote liquid film drainage, leading to bubble rupture. The liquid discharge rate of foam can reflect the stability of foam. Adding a substance to promote the liquid discharge of foam can also play a role in defoaming.
4.Adding hydrophobic solid particles can cause bubble rupture.
The hydrophobic solid particles on the surface of bubbles attract the hydrophobic end of surfactants, causing hydrophobic particles to develop hydrophilicity and enter the aqueous phase, playing a defoaming role.
5.Solubilizing and foaming surfactants can cause bubble collapse
Some low molecular substances that can mix well with the solution can increase the solubility of bubble surfactants and reduce their effective concentration. Low molecular substances such as octanol, ethanol and propanol can not only reduce the concentration of surfactant in the surface layer, but also dissolve the surfactant adsorption layer to reduce the intermolecular compactness of surfactant, thus reducing the stability of foam.
6.Electrolyte disintegration surfactant double layer
A stable foaming solution can be formed by the interaction of the surfactant double electric layer of foam. The addition of ordinary electrolytes can achieve defoaming effect by dissolving the surfactant bilayer.