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Detergent foam
Release Date：2016-3-16 Source：xiashundong Views：1249
Foam plays an important role during the washing process. A gas bubble is dispersed in a liquid or solid dispersion, the dispersed phase as a gas, liquid or solid dispersion medium, the former is referred to as liquid foam, while the latter is referred to as a solid foam, such as foam, foam glass, foam cement.
(1) Formation of foam
We are talking here of the foam, it is separated by means of liquid film bubble aggregates. This foam due to the density of the dispersed phase (gas) and the dispersion medium (liquid) of the difference between the larger, combined with a low viscosity liquid, so bubbles always rise to the level quickly.
The process of forming the foam is a lot of gas into the liquid, bubbles in the liquid is quickly returned to the surface, is formed by a small amount of liquid and gas bubbles separated aggregates
Foam on the form with two notable features: one is as a dispersed phase is in the form of bubbles often polyhedral shape, it is because at the intersection of the bubble, there is a thin film of air bubbles become trend polyhedron, when the film thinned to a certain extent, resulting in the collapse of bubble; the other is not pure liquid form stable foam, liquid foam can be formed, at least two or more components. Aqueous surfactant solution is typically easy to produce foam system, its ability to generate foam and other properties also have a certain relationship.
Good foaming power of surfactants known as foaming agents. Although the foaming agent foams having good capacity, but may not be able to maintain the foam formed longer time, i.e., stability is not necessarily good. In order to maintain a stable foam, foaming agents often added to increase the stability of the foam material, a substance known as foam stabilizer, conventional foam stabilizer has lauroyl diethanolamine and lauryl dimethyl amine oxide.
Stability (2) foam
Foam is a thermodynamically unstable system, and finally the trend of the total surface area after defoaming the liquid in the system is reduced, reducing free energy. Anti-foaming process gas is separated by the thickness of thin film, until the rupture process. Therefore, the stability of the foam is primarily liquid discharging speed and film strength determined. The factors are the following.
① surface tension
From the viewpoint of energy, low surface tension more favorable for the formation of bubbles, but we can not guarantee a stable foam. Low surface tension, pressure difference, draining slow, slower thin film, there is conducive to the stability of the foam.
② surface viscosity
Decision key factor is the stability of foam film strength, and the film strength is mainly determined by surface adsorption of membrane robustness, surface to measure its viscosity. Experiments show that the surface of the high viscosity of the generated foam solution longer life. This is because the interaction between the adsorbed molecules cause the film strength is increased, thereby increasing the life of the foam.
③ solution viscosity
When the liquid viscosity increases itself, difficult to discharge the liquid film, thin film thickness slower, delaying the film rupture time and increases the foam stability.
④ "fix" the effect of surface tension
Surfactant adsorbed on the surface of the film, there is the ability to resist expansion or contraction of the liquid film surface, we will this ability is called repair. This is because the surfactant film on the surface of adsorption, expansion of the surface area will reduce the concentration of adsorbed molecules of the surface, increase the surface tension. Further expand the surface will need to do more work. On the other hand the surface area of the contraction will increase the concentration of adsorbed molecules, which reduce the surface tension is not conducive to a further contraction.
⑤ gas diffusion through the film
Due to the capillary pressure, the pressure in the foam bubbles than the big bubble of high pressure will cause the vesicles to large gas bubble through the liquid film diffusion and low pressure, resulting in smaller vesicles, bullae becomes large, the final foam cracking phenomenon. If the addition of a surfactant, foaming will enable uniform fine foam, easy defoaming. Since the surface-active agent tightly arranged on the film, breathable difficult, leaving the foam more stable.
Influence of surface charge
⑥If the foam film with a charge of the same sign, both surfaces of the film repel each other, preventing the destruction of the film even thinner. Ionic surfactants may play a role in this stabilization.
In summary, the film strength is a key factor in determining the stability of the foam. As a foaming agent and a foam stabilizer surfactants, surface adsorbed molecules arranged closely and fastness are the most important factor. Strongly adsorbed molecular interactions, the compact arrangement of adsorbed molecules, which not only makes the surface film itself has high strength, but because of high viscosity so that the surface adjacent the surface film was easy flow, is relatively difficult to discharge the liquid film, film the thickness is easy to maintain. In addition, the closely spaced surface molecules can reduce the permeability of the gas molecules and thus also increase the stability of the foam.
Destruction (3) foam
The basic principle is to change the conditions to break the foam or foam stabilizing factor in the elimination of foam, which has two kinds of physical and chemical defoaming method.
Physical defoaming foam solution is maintained at a constant chemical composition of the foam produced by changing conditions, such as external disturbances ﹑ temperature or pressure changes and sonication are all methods to eliminate significant physical foam.
Defoaming method is to add certain chemical substances and foaming agents play a role, reducing the strength of the foam in the liquid film and thus reduce the foam stability in order to achieve the purpose of anti-foaming, such substances are called defoamers. Most defoamer surfactant. Therefore, according to the mechanism of defoaming, a defoaming agent should have the ability to reduce the surface tension, readily adsorbed on the surface, and the interaction between the adsorbed molecules is weak, looser structure of adsorbed molecules aligned.
Defoamers diverse types, but basically a non-ionic surfactant. Non-ionic surface active agent having anti-foam properties at or near its cloud point above the cloud point, often used as defoamers. Alcohols, especially fatty alcohols and fatty acid esters ﹑ branched structure ﹑ ﹑ multi amide phosphate ﹑ silicone oil is also commonly used excellent defoamers.
(4) Foam & Care
Bubbles and washing effect, and there is no direct link does not indicate how much the amount of foam washing effect is good or bad. For example sudsing nonionic surfactants is far better than soap, but it is much more excellent detergency than soap.
In some cases, the foam to remove dirt aspect is helpful. For example: When the family washing dishes, washing liquid foam can be washed down droplets away; scrub carpet, foam helps to take away the dust ﹑ powder and other solid dirt. In addition, sometimes the foam can be used as a washing liquid is valid flag as fatty oil washing liquid foam inhibited when the oil is excessive, less detergent when there will be no foam generation, or so that the original foam disappears. Sometimes foam can also be used as an indicator of rinsing is clean, because the amount of foam rinse often with decreasing detergent content is reduced, it is possible to evaluate how much the amount of foam to the extent of rinsing.
(1) Formation of foam
We are talking here of the foam, it is separated by means of liquid film bubble aggregates. This foam due to the density of the dispersed phase (gas) and the dispersion medium (liquid) of the difference between the larger, combined with a low viscosity liquid, so bubbles always rise to the level quickly.
The process of forming the foam is a lot of gas into the liquid, bubbles in the liquid is quickly returned to the surface, is formed by a small amount of liquid and gas bubbles separated aggregates
Foam on the form with two notable features: one is as a dispersed phase is in the form of bubbles often polyhedral shape, it is because at the intersection of the bubble, there is a thin film of air bubbles become trend polyhedron, when the film thinned to a certain extent, resulting in the collapse of bubble; the other is not pure liquid form stable foam, liquid foam can be formed, at least two or more components. Aqueous surfactant solution is typically easy to produce foam system, its ability to generate foam and other properties also have a certain relationship.
Good foaming power of surfactants known as foaming agents. Although the foaming agent foams having good capacity, but may not be able to maintain the foam formed longer time, i.e., stability is not necessarily good. In order to maintain a stable foam, foaming agents often added to increase the stability of the foam material, a substance known as foam stabilizer, conventional foam stabilizer has lauroyl diethanolamine and lauryl dimethyl amine oxide.
Stability (2) foam
Foam is a thermodynamically unstable system, and finally the trend of the total surface area after defoaming the liquid in the system is reduced, reducing free energy. Anti-foaming process gas is separated by the thickness of thin film, until the rupture process. Therefore, the stability of the foam is primarily liquid discharging speed and film strength determined. The factors are the following.
① surface tension
From the viewpoint of energy, low surface tension more favorable for the formation of bubbles, but we can not guarantee a stable foam. Low surface tension, pressure difference, draining slow, slower thin film, there is conducive to the stability of the foam.
② surface viscosity
Decision key factor is the stability of foam film strength, and the film strength is mainly determined by surface adsorption of membrane robustness, surface to measure its viscosity. Experiments show that the surface of the high viscosity of the generated foam solution longer life. This is because the interaction between the adsorbed molecules cause the film strength is increased, thereby increasing the life of the foam.
③ solution viscosity
When the liquid viscosity increases itself, difficult to discharge the liquid film, thin film thickness slower, delaying the film rupture time and increases the foam stability.
④ "fix" the effect of surface tension
Surfactant adsorbed on the surface of the film, there is the ability to resist expansion or contraction of the liquid film surface, we will this ability is called repair. This is because the surfactant film on the surface of adsorption, expansion of the surface area will reduce the concentration of adsorbed molecules of the surface, increase the surface tension. Further expand the surface will need to do more work. On the other hand the surface area of the contraction will increase the concentration of adsorbed molecules, which reduce the surface tension is not conducive to a further contraction.
⑤ gas diffusion through the film
Due to the capillary pressure, the pressure in the foam bubbles than the big bubble of high pressure will cause the vesicles to large gas bubble through the liquid film diffusion and low pressure, resulting in smaller vesicles, bullae becomes large, the final foam cracking phenomenon. If the addition of a surfactant, foaming will enable uniform fine foam, easy defoaming. Since the surface-active agent tightly arranged on the film, breathable difficult, leaving the foam more stable.
Influence of surface charge
⑥If the foam film with a charge of the same sign, both surfaces of the film repel each other, preventing the destruction of the film even thinner. Ionic surfactants may play a role in this stabilization.
In summary, the film strength is a key factor in determining the stability of the foam. As a foaming agent and a foam stabilizer surfactants, surface adsorbed molecules arranged closely and fastness are the most important factor. Strongly adsorbed molecular interactions, the compact arrangement of adsorbed molecules, which not only makes the surface film itself has high strength, but because of high viscosity so that the surface adjacent the surface film was easy flow, is relatively difficult to discharge the liquid film, film the thickness is easy to maintain. In addition, the closely spaced surface molecules can reduce the permeability of the gas molecules and thus also increase the stability of the foam.
Destruction (3) foam
The basic principle is to change the conditions to break the foam or foam stabilizing factor in the elimination of foam, which has two kinds of physical and chemical defoaming method.
Physical defoaming foam solution is maintained at a constant chemical composition of the foam produced by changing conditions, such as external disturbances ﹑ temperature or pressure changes and sonication are all methods to eliminate significant physical foam.
Defoaming method is to add certain chemical substances and foaming agents play a role, reducing the strength of the foam in the liquid film and thus reduce the foam stability in order to achieve the purpose of anti-foaming, such substances are called defoamers. Most defoamer surfactant. Therefore, according to the mechanism of defoaming, a defoaming agent should have the ability to reduce the surface tension, readily adsorbed on the surface, and the interaction between the adsorbed molecules is weak, looser structure of adsorbed molecules aligned.
Defoamers diverse types, but basically a non-ionic surfactant. Non-ionic surface active agent having anti-foam properties at or near its cloud point above the cloud point, often used as defoamers. Alcohols, especially fatty alcohols and fatty acid esters ﹑ branched structure ﹑ ﹑ multi amide phosphate ﹑ silicone oil is also commonly used excellent defoamers.
(4) Foam & Care
Bubbles and washing effect, and there is no direct link does not indicate how much the amount of foam washing effect is good or bad. For example sudsing nonionic surfactants is far better than soap, but it is much more excellent detergency than soap.
In some cases, the foam to remove dirt aspect is helpful. For example: When the family washing dishes, washing liquid foam can be washed down droplets away; scrub carpet, foam helps to take away the dust ﹑ powder and other solid dirt. In addition, sometimes the foam can be used as a washing liquid is valid flag as fatty oil washing liquid foam inhibited when the oil is excessive, less detergent when there will be no foam generation, or so that the original foam disappears. Sometimes foam can also be used as an indicator of rinsing is clean, because the amount of foam rinse often with decreasing detergent content is reduced, it is possible to evaluate how much the amount of foam to the extent of rinsing.