defoam

Defoam, or defoaming, refers to the practice of reducing or eliminating foam in liquids. In industrial processes, foam can hinder heat transfer, trap products, cause overflow, or disrupt downstream equipment, making defoaming an important control measure. Defoaming agents, often called anti-foams or defoamers, work to destabilize the air–liquid interface and promote rupture and drainage of entrained bubbles.

Defoaming mechanisms vary by agent and system but commonly include adsorption at bubble interfaces to change surface properties, rupture of thin liquid films, and enhanced drainage from the foam structure. Some defoamers provide a lubricating or spreading action at the bubble surface, while others create conditions that favor bubble coalescence and collapse. The effectiveness of a defoamer depends on factors such as temperature, shear, pH, salinity, and the presence of surface-active substances in the liquid.

Types of defoamers typically include silicone-based oils (organosiloxanes), mineral or vegetable oils, and fluorinated or hydrocarbon compounds, often formulated as oils, emulsions, or dispersions. Water-dispersible or polymer-based defoamers are used in systems where a liquid-stable dispersion is required. Selection depends on compatibility with the product, process conditions, and potential impact on taste, odor, color, or viscosity.

Applications span many industries, including pulp and paper, wastewater treatment, fermentation and brewing, dairy and food processing, cosmetics, paints and coatings, and petrochemicals. Effective dosing is usually small (low parts per million to a few thousand per million) and requires testing to balance foam control with product quality and process performance.