Defoaming

Water-based systems, such as polymer dispersions or metalworking fluids contain amphiphilic components such as emulsifiers, dispersants or wetting agents. While these components are essential to the product's performance, they often create foam during production or application. In order to avoid the formation of foam, and ensure optimal product performance foam control agents are required.

Defoamers need to form separate droplets in the system in order to work. The mode of action of foam control agents can very briefly be described by first entering the air/water interface, followed by spreading within this interface. There are quite a few excellent reviews discussing various mechanisms how foam control agents are working; these are recommended for further reading [1], [2].

Since foam control agents have to form separate droplets in the system they are supposed to work in, the defoamers can not be compatible with the matrix. This incompatibility can also lead to problems in the applications, e.g. to surface defects. But if one choses a defoamer which is too compatible, it will loose its effectivity completely. So there is a quite delicate balance which needs to be considered. Taking into account the many different formulations consisting of different base liquids and containing different kinds of amphiphilic additives, it is obvious that there can not be a universal defoamer!

These are some of the parameters which are considered when formulating foam control agents:

• Oil phase: Its chemistry determines the (in)compatibility with the matrix, the surface and interfacial tensions, the viscosity etc. Depending on the requirements, oil phases in foam control agents can consist of silicone oil, organomodified siloxanes, polyethers, mineral oils, ester oils, or mixtures therof.
• Particles: The effectivity of foam control agents can be greatly improved by the incorporation of particles, and again there are many parameters which are very important: The chemistry, especially the surface chemistry (i.e. hydrophobicity), size distribution and shape of the particles.
• Emulsion: Many foam control agents are supplied as an oil-in-water emulsion, providing the defoamer oil droplets already in the optimum size required in the application. Again, there are quite a few parameters such as the emulsifier system, rheological additive and droplet size distribution which are extremely important when formulation effective foam control agents.

So if you have a foam problem, just rely on our longtime experience in formulating foam control agents.

[1] R.J. Pugh: Foaming, foam films, antifoaming and defoaming, Adv. Colloid Interf. Sci. 64 (1996) pages 67-142.
[2] Nicolaii Denkov: Mechanism of foam distruction by oil-based antifoams, Langmuir 20 (2004) 9463-9505