How to Choose Defoamer Powder?

Foam is created when gas is introduced and trapped within a solution that contains surfactants. It can consist of large bubbles at the surface of the solution (macrofoam) or small bubbles distributed throughout the solution (microfoam). In either case, it can cause issues within the products and equipment in which it is formed, such as lower product quality, inconsistent product density, and machine damage.

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Antifoam and defoaming agents are key to preventing and controlling foam and avoiding the problems associated with it. Both compounds minimize or eliminate foam formation. However, they achieve this goal in different ways; antifoams are surfactants that prevent foam from forming in the first place, while defoamers are surfactants that control existing foam levels by stopping the bubbles from stabilizing.

There are two things an antifoam or defoamer must have to work: an entry coefficient greater than zero and a spreading coefficient greater than zero. These qualities allow the compound to enter the interface between the air and lamella (i.e., the bubble wall) and then enter the bubble wall in a process known as “bridging the film”. As it spreads, the bubble wall thins and, eventually, ruptures.

Beyond the above properties, an antifoam or defoamer can vary in many ways. For example, it can have a silicone or non-silicone composition, be aqueous or non-aqueous, and come in liquid or powder form. This broad selection enables industry professionals to choose a foam control product that meets their exact application requirements. However, it can make it challenging to identify which one best suits their needs. Below, we cover the key factors to keep in mind when selecting an antifoam or defoaming agent.

Factors to Consider When Choosing an Antifoam/Defoamer

In aqueous environments, the right antifoam or defoamer product can minimize or eliminate issues associated with foam. Some of the questions you should answer before choosing an antifoam or defoamer for a given application include:

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• Is the antifoam/defoamer compatible with the process? Antifoams and defoamers are generally inert chemicals consisting of a liquid (e.g., silicone, mineral oils, or hydrophobic surfactants) and a hydrophobic solid (e.g., fatty acids, fatty alcohols, silica, or wax). Ultimately, the antifoam/defoamer you select should have a balance of compatibility and incompatibility. It should be compatible enough that it effectively disperses in the foaming medium. Otherwise, it may cause deposition issues. However, it should be insoluble to the point that it remains in fine droplet form within the solution.
• Will the antifoam/defoamer cause deposit issues? The antifoam/defoamer should be sufficiently compatible within the solution so as to not create deposits.
• Will the antifoam/defoamer negatively affect the catalyst I am using? The antifoam/defoamer should not negatively impact any catalysts used in the process.
• Will the antifoam/defoamer plug up any membranes or filters? The antifoam/defoamer should not carry the potential for plugging/clogging filters and membranes that can compromise the product or process.
• Is the antifoam/defoamer composition effective for my application? Antifoams and defoamer come in many varieties. The one you choose should suit your individual requirements and restrictions.
• Will the antifoam/defoamer have any negative effects on downstream conditions? The antifoam/defoamer should not cause any adverse downstream effects.

The answers to these questions must be weighed appropriately. In some cases, you must compromise on a solution.

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Antifoaming agents are substances with lower surface tension and higher surface activity, which can inhibit and eliminate foam in liquids, which means that antifoaming agents can reduce the surface tension of water, solutions, suspensions, etc so then some bubbles are eliminated. Sometimes defoaming is also called anti-foaming agent. The time of anti-foaming is the main symbol of the quality of the antifoaming agent. In most cases, the key property of anti-foaming agent is to evaluate the time of foam suppression, rather than the initial time of killing foam. But defoaming and foam suppression are relative. Gernarally speaking, products with good defoaming performance will have relatively poor foam suppressing performance.

Some components of water-based adhesives are easy to produce bubbles and have a tendency to be stable and lasting. In addition, the rapid stirring during production and the high-speed brushing construction during use also contribute to the generation of foam, which prevents the production from proceeding normally and affects the product quality. The formation of foam is very difficult to produce and apply tape, and the pores of the adhesive layer appear, which affects the outside of the product and the adhesive performance. Therefore, it is necessary to try to destroy the foam or prevent the generation of foam. The most effective method is to use an antifoam agent.

Silicone defoamers have strong defoaming and anti-foaming performance, and are widely used in the coating industry. In the water-based adhesive industry, especially emulsion-type low-viscosity systems, such as laminating adhesives and pressure-sensitive adhesives, it is easy to cause problems such as shrinkage and fish eyes. In addition, after the film formation of the emulsion, due to the surface migration of silane, it will cause a decrease in the bonding strength at a later stage and affect the bonding effect, so it is generally rarely used.

Mineral oil defoamers are commonly used in the water-based pressure-sensitive adhesive and laminating adhesive industries. It is mainly composed of mineral oil, hydrophobic particles, fatty alcohol, emulsifier, etc. The quality of these products is susceptible to mineral oil grades and batch differences. Because the entire system is a thermodynamically unstable system, it is easy to delaminate. It mainly depends on its dispersion in the emulsion to provide defoaming effect. The effect of surfactants, mineral oil defoamers are easy to slick in these systems, which will cause the defoaming effect to decrease seriously, and the uneven distribution of mineral oil will also affect the coating effect, which gives our production And application cause great trouble.

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