ANTI-FOAM

defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably. Strictly speaking, defoamers eliminate existing foam and anti-foamers prevent the formation of further foam. Commonly used agents are insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols. The additive is used to prevent formation of foam or is added to break a foam already formed.

In industrial processes, foams pose serious problems. They cause defects on surface coatings and prevent the efficient filling of containers. A variety of chemical formulae are available to prevent formation of foams

Generally a defoamer is insoluble in the foaming medium and has surface active properties. An essential feature of a defoamer product is a low viscosity and a facility to spread rapidly on foamy surfaces. It has affinity to the air-liquid surface where it destabilizes the foam lamellas. This causes rupture of the air bubbles and breakdown of surface foam. Entrained air bubbles are agglomerated, and the larger bubbles rise to the surface of the bulk liquid more quickly

Types of defoamers

There are two common types of defoamers, silicone based and silicone free, with each type of defoamer being either a liquid or powder formulation.  

  1. Silicone based defoamers

    1. Liquid formulation

      • Has a silicone backbone consisting of hydrophobic silica in silica oil.
      • Chemically inert, thermally stable, low surface tension, and completely soluble in water.

    2. Powder formulation

      • Composed of a silicone antifoam compound.
      • Have excellent defoaming action and are stabile in small concentrations.

  1. Silicone free defoamers 

    1. Liquid formulation

  • Most effective in water based and solvent based systems. 
  • Controls foam regeneration and doesn’t cause discoloration. 

b. Powder formulation

  • Composed of silicone antifoam compounds.
  • Excellent defoaming action and have lasting defoaming power and stability in small concentrations.