It is not only worth considering polysiloxanes as defoamers, there are also other polymer compounds that have a defoaming effect as a result of their incompatibility. Finding the right balance between “incompatible” and “compatible” is achieved by selective changes to the polarity and molecular weight (molecular weight distribution) of the polymer structures.
Polymer Defoamers for Water-based Systems
The polymers need to be insoluble in water. It is important for the polymers to have a low surface tension and spread well over the surface. For polymer defoamers in water-based systems, hydrophobic particles are used to improve the defoaming action. Chemically, the particles are based on hydrophobic silicas, polyurea or polyamide.
Polymer Defoamers for Solvent-borne and Solvent-free Systems
Non-polar and branched polymers are well suited to solvent-borne and solvent-free systems as active defoaming agents. The polymer needs to be active at the surface and interfaces. The compatibility and polarity of the polymers can be adapted accordingly by selecting the molecular weight or monomer.
BYK‑354, BYK‑355, BYK‑361 N, BYK‑390 and BYK‑392 cannot remain unnamed in this discussion. These products, though primarily acrylate-based leveling additives, are also used frequently in numerous systems as defoamers or air release agents. BYK‑390 and BYK‑392 are recommended for preventing popping in baking coatings.