How to Make Defoaming Agent

Foam formation in coating films can cause surface defects such as fisheyes, craters or pinholes to form. To stop it happening again, formulators use antifoam and defoamer additives – however their selection and evaluation require in-depth knowledge of their mechanism of action in different coating systems.

An effective defoamer must be soluble in the foaming medium, penetrating into foam lamellae quickly, and spreading rapidly along the gas-liquid interface.

Polydimethylsiloxane (PDMS)

PDMS is an economical, biocompatible material with many uses in microfluidics. It can be attached to polymers, glass and metal components to form embedded devices; used as an electroosmotic pumping membrane and even pattern using photoresist to form microfluidic channels.

To address this, PDMS can be oxidized using oxygen plasma, opening up hydroxyl groups on its surface that react with silyl chloride vapors to form terminal groups for defoaming agents to react with. As a result, defoaming agents reacted with this surface exhibit reduced foaming and inhibition than traditional silicone defoaming additives, plus they’re nontoxic, easy to disperse, and thermally stable compared to their silicone counterparts.

Silicone Oils

Silicone oils rely on specific gravity differences between aqueous humor and silicone oil for their defoaming mechanism, with higher specific gravity of aqueous humor causing it to sink inside vitreous cavities while lower specific gravity of silicone oil causes it to float, creating what is known as buoyancy forces which elevate it upward.

Medical-grade silicone oils can be effective defoaming agent due to being lighter than water and altering surface tension to cause foam bubbles to burst. Furthermore, they’re nontoxic and easy to dissolve into aqueous solutions.

silicone-based antifoaming agents require high concentrations of silicones that may be toxic and detrimental to human health, while vegetal oils like jojoba oil have similar antifoaming capabilities but with much lower efficiency; furthermore, their low water content makes dispersion more challenging than expected.

Mineral Oils

Mineral oils are colorless, odorless mixtures of higher alkanes derived from mineral sources that are produced as byproducts from processing crude oil into petroleum products. Historically they were also known as white or paraffin oil due to the imprecision of their name reflecting that oftentimes merchants did not need or wish to know exactly the makeup of each mineral oil that was sold or used as merchant goods (Merriam-Webster dates first use of “mineral oil” back to 1771!).

Mineral oil can be further refined for industrial uses to remove additives that could potentially be harmful for human consumption, producing refined mineral lubricant suitable for food products and pharmaceutical products that could come into contact with food, including any potential accidental food contact issues.

Food grade mineral oils are generally tasteless and odorless oils soluble in water that provide excellent corrosion protection, making them safe to be in direct contact with skin. Furthermore, they help keep dehydration at bay by acting as a protective barrier that limits trans-epidermal water loss.

Water Soluble defoamer

Water-soluble defoamer offer excellent defoaming properties and can be made by mixing a polyether modified organic silicon compound with lower alcohols, surfactants and silica. When compared with traditional mineral oils, this defoamer offers the advantages of predispersion and requires less energy for incorporation into coating systems.

Defoaming agent work by remaining insoluble in the foaming medium and preventing close association between molecules at the surface of film, thereby preventing surfactants with foam stabilization from restoring film elasticity via Marangoni effects and thus preventing foam formation. Furthermore, defoamer work by encouraging drainage of liquid film from foam bubbles so they burst.