Defoamers

Defoamers with a high hydrophobicity have limited solubility in water and are not easily incorporated into aqueous solutions, which, for the most part, comprise the water reducing admixture compositions (27). This hydrophobicity tends to destabilize the aqueous product and fosters separation of components. It requires that 

Air entrainment and foaming in hydrocarbon liquids can cause operational problems with high-speed machinery in physical-chemical processes such as petroleum production, distillation, cracking, coking, and asphalt processing. 

Defoamer formulations currently contain numerous ingredients to meet the diverse requirements for which they are formulated. Various classification approaches are possible, including classification by application, physical form of the defoamer, and the chemical type of the defoamer. In general, defoamers contain a variety of active ingredients, both in solid and in liquid states, and a number of ancillary agents such as emulsifiers, spreading agents, thickeners, preservatives, carrier oils, compatibilizers, solvents, and water. 

Active ingredients are the components of the formulation that control the actual foaming. These may be liquids or solids. 

Because lowering the surface tension is the most important physical property of a defoamer, it is reasonable to classify the defoamer by the hydrophobic operation of the molecule. In contrast, the classification of organic molecules by functional groups are often polar and hydrophilic (i.e., alcohol, acid, and salt are common in basic organic chemistry). Four classes of defoamers are known as liquid phase components  

dispersed solids are active in defoaming in suitable formulations. Some liquid defoamers are believed to be active only in the presence of a solid. It is believed that a surface-active agent present in the system will carry the solid particles in the region of the interface and the solid will cause a destabilization of the foam. 

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