Abstract

A review is presented of the materials used to control or eliminate foam in industrial processes and how they function. These materials are classified by their chemical type. Main active liquid-phase components are hydrocarbon oils, polyethers, and silicone fluids; main solid-phase components are waxy hydrocarbons and hydrophobic silica. Ancillary agents such as surfactants and carriers are also incorporated in some defoamer formulations. Sources of significant commercial defoamer products are listed. The theory of foaming and defoaming is outlined with emphasis on surface behavior such as entering, spreading, and dewetting phenomena. The role of dispersed hydrophobic solids is highlighted. Applications in various areas are briefly reviewed, including adhesives and sealants, chemical processing, cleaning compounds, construction, fermentation processes, fertilizers, food and beverages, leather, metal working, oil and petrochemicals, coatings, polymers, pulp and paper, textiles, and wastewater treatment. Economic and health and safety factors are considered. Test methods, such as pneumatic, dynamic, shaking, pour, stirring, and blending methods are also briefly reviewed.