Frequently Asked Questions

Although the terms defoamer and antifoam are often used interchangeably, they have different intended purposes. The primary distinction between defoamers and antifoams is that defoamers are meant to control the amount of existing foam, whereas antifoaming agents are designed to prevent foam from forming in the first place.

Defoamers typically contain a carrier fluid, which can be silicone oil, hydrocarbon oil, synthetic polymer, vegetable oil, etc. In addition, defoamers feature active ingredients that help destabilize foam, such as salts, metal, silica, or other hydrophobic particles.

An emulsification system can help optimize the compatibility and spreading of the defoamer within a foaming system. Depending on the chemistry, stabilizing agents such as acrylic or cellulosic thickeners may be incorporated to enhance shelf stability.

As foam bubbles collect and merge at the surface interface, the bubble walls begin to thin and break. Defoamers help accelerate the process, breaking all the bubbles, including the smaller ones. Typically, defoamers have surface-active properties and are insoluble in the foaming medium.

Defoamers work by entering the bubble wall (lamella) in a process known as “bridging of the film.” During this process, the lamella is bridged by a defoamer droplet or hydrophobic particle such as silica. Once the defoamer enters the lamella, it creates a lens that will start to spread, causing the bubble wall to thin. The thickness of the lens also thins as it spreads, and movements in the medium alter its shape.

Stresses occur until the lens breaks, rupturing the lamella. The resulting lens has significantly less elasticity compared to the surfactant lens, which before application, stabilized the lamella. The destabilization caused by the film facilitates the rupture of the lamella. Defoamers destroy existing foam with the same mechanisms employed by antifoams.

The antifoam market consists of mainly silicone-based products because of their inherent properties, which include:

• Chemical inertness
• Insoluble in water
• Low surface tension
• Thermal stability

Silicone-based antifoams contain silicone, a polymer derived from a silicon backbone. These antifoams are usually presented as water-based emulsions but can also be non-aqueous. They spread through foam quickly due to their low surface tension. These types of antifoams can easily float over the foam wall, occupying openings to make the foam wall thin and eventually collapse.

Antifoams can also include organic-based and non-silicone products, but their use has been significantly reduced in certain applications because of the overall effectiveness of silicone-based products. However, they still apply in many settings, including process waters and effluent treatments where silicone products aren’t permitted.

Defoamers prove beneficial in various industrial applications and products, including inks, paints, adhesives, and coatings. Other defoamer applications include:

• Cutting fluids
• Food processing
• Hydraulics
• Industrial wastewater treatment
• Machine tools
• Oil drilling
• Paint
• Paper
• Wood pulp

Antifoam agents can be added to some cleaning products and detergents to help reduce foaming. When used as a process aid or food additive, antifoams control foam and fizziness in manufacturing and packaging. Antifoam agents are also available as pharmaceuticals for human consumption to relieve gas and bloating.