Foam is an unwanted by-product of the processing or mixing of liquids. In adhesives, unchecked foam increases the volume of the liquid, which can reduce batch and packaging yields, cause tank overflows, pump cavitation, and reduce the efficiency of coating operations. Foam can also contribute to poor product quality by destabilizing emulsions, reducing adhesion capabilities or creating surface defects and decreasing aesthetic properties.

Foam control agents can be added to destabilize existing foam or prevent stable foam from forming. These can be classified as:

  • Defoamers: Added to reduce or eliminate pre-existing foam
  • Anti-foaming agents: Added to prevent the formation and stabilization of foam
  • Air release agents: Added to removed entrained air from the bulk fluid and raise micro-foam to the surface.

Many foam control agents can assist in both preventing and eliminating foam, so these terms are often used interchangeably. To simplify the terminology, “defoamer” is generally used as a standard term.