The defoamer effect

Imagine you want to treat yourself to a glass of beer. In your excitement you pour the bottle too fast, and foam rises, spilling beer across the table.

The producers of liquid products know that problem too: When you fill shampoo in bottles or petrol into tanks, you must manage spilled liquids caused by the foam. Besides that, unwanted foam reduces the filling volume in containers, causes imperfections in coatings, makes concrete less stable, or causes production shutdowns because pumps can’t work properly.

Foam bubbles look cute and harmless, yet they are notorious for causing problems in industrial production. So, a lot of producers of foaming liquids use an army of tiny knights to pop all bubbles within the production process. Usually, this army consists of water-insoluble oils. The oil droplets push between the bubbles and force them to burst.

But oil droplets alone are often not efficient enough. That’s why hydrophobic silica is added. Silica particles made of silicon dioxide (SiO₂) have a very porous geometry. That’s why they can absorb the oil droplets by using capillary forces. Like ships transporting knights with lances, our silica particles carry the oil droplets directly into the water-air boundary layer of a foam lamella, where they can do their defoaming job. Only small doses of finely dispersed hydrophobic silica are needed to give defoamers a significant efficiency boost.

Our silica not only carries the oils of defoamers, but also vitamins, fragrances, flavors, organic acids, and many more. This makes them a useful ingredient for pills, cosmetics, food, or feed. If this carrier effect is the topic you are interested in, you will find lots of useful information here. 

From paper mills  to the production of car coatings, from concrete  to the processing of jam: The application areas of defoamers are very different, but the basic principle is always the same. Let’s zoom in …

Foams are dual-phase systems of gas bubbles trapped in a liquid matrix. The liquid could be an aqueous solution in which surfactant molecules concentrate at the gas-liquid phase boundary to stabilize the foam. To destabilize that “skeleton” of the foam, oil droplets of a defoamer formulation need to penetrate the so-called plateau border. That’s where our carrier silica comes into play.

Silica particles are like public buses: They incorporate your oil droplets and carry them right into the surfactant monolayer at the air/water interface. You just have to choose the right bus line: In our portfolio we provide silica with a wide range of hydrophobic properties. Choose the one that matches the liquid you want to defoam and the bus will carry your oil droplets directly to the air/water interface. Once there, they remain in place and efficiently prevent new bubble formation.

Our efficiency enhancers work at low concentrations and in nearly every process, thanks to their resistance to high temperatures, high pH values, or high shear forces. We offer silica for both liquid and dry defoamers.

To take full advantage of our performance booster, the silica must be evenly distributed in the defoamer oil, for example by using a rotor-stator system, a dissolver disc, toothed blade, or rotor-stator mixers. The compound created is processed afterwards with other ingredients to become your finished defoamer.

At Evonik, we offer ready-to-use hydrophobic silica products, for easy addition to your defoamer formulations, as well as reactive silica for defoamer manufacturers that prefer to do the hydrophobic treatment in their formulation by themselves.

When you use our silica carrier to boost the defoaming effect of your formulation, you get the rheology effect for free. The added silica will stabilize the emulsion of your defoamer, which means that your product can be stored longer. Smaller amounts are discarded due to decay, which is good news for mother nature.

But is it safe? Yes, it is. Silica has great effects on the properties of your products – but it has nearly no effect on people. That’s why it is approved for use in feed, food, and pharmaceuticals. For example, the European Food Safety Authority regularly confirms the safety of silica as an additive for food. Additionally, our silica agents have received OMRI Listed® Certification, proving their suitability for organic farming. If you want to find out more, you can get some useful information on the safety of silica on our FAQs page. 

Simply write an email to ask-se@evonik.com or press the contact button above. Your message will be forwarded to one of our silica specialists and they will respond to you as quickly as possible.

Are you already one of our customers? Then you will get support from your regional contact and from our application engineers. We are looking forward to helping you!