Both antifoams and defoamers are used for foam control. Given their similarities in function, they often have similar chemistries. The main difference between them is the timing of application. In order to prevent it, antifoams are designed to be applied before the formation of foam, while defoamers are designed to be applied after foam formation in order to destroy it. Below, we provide a closer look at antifoam and defoamer chemistry.
The Chemistry of Antifoams
Antifoams are typically inert chemicals. They consist of a liquid component (e.g., nonionic surfactant, mineral oil, and/or silicone) and a hydrophobic solid (e.g., wax, fatty acid/alcohol, and/or hydrophobic silica). They must be sufficiently incompatible such that they are insoluble with the medium. Otherwise, they will not mitigate foam as effectively. However, they must also be sufficiently compatible such that they do not cause deposition problems.
There are many types of antifoams available, and they are often lumped into two broad categories:
- Silicone Antifoams. Silicone antifoams are normally composed of hydrophobized silica that is finely dispersed within a silicone fluid. The resulting compound is then stabilized into a water-based or oil-based emulsion. These antifoams are highly effective due to their general chemical inertness, potency even in low concentrations, and ability to spread over a foam film. If needed, they can be combined with other hydrophobic solids and liquids to improve their defoaming properties.
- Non-Silicone Antifoams. Non-silicone antifoams generally contain surfactants, which enhance their dispersal capabilities and effectiveness in foaming water. They can be water-based, oil-based, or surfactant-based. These antifoams can be used for a wide range of industries. Compared to silicone antifoams, they are sometimes more readily biodegradable and less prone to causing certain problems such as discoloration, spotting, and negative membrane effects.
The Chemistry of Defoamers
Defoamers share many of the same chemical characteristics as antifoams. For example, they are typically made of a liquid component and a hydrophobic solid, although some are strictly liquid. Additionally, they are formulated for a balance between solubility and insolubility with the medium that ensures effective foam control performance.
These foam control products come in many variations, of which one type is oil-based defoamers. Oil-based defoamers are typically of the “non-silicone” variety, but their composition can be highly variable and include chemical species ranging from hydrophobic solids to esters to silicones. They offer high efficacy at lower dosages, making them a preferred choice for foam knockdown in many applications.
How Do I Select the Most Effective Antifoam/Defoamer for My Application?
The type of foam generated and the timing of its production vary from process to process. That’s why it is important to choose a foam control solution with a chemistry that is appropriate for your specific application. It is advisable to test a primary and a secondary foam control product. If you want more information on how to select an effective foam control solution or if you would like samples to evaluate, Applied Material Solutions (AMS) is here to help. We have extensive experience producing a broad selection of foam control compounds for use in a wide range of industries and applications. One of the eBooks we’ve put together, “Must-Ask Questions When Choosing a Foam Control Agent,” has many of the answers to any questions you may have about the selection process. Alternatively, you can contact us today.