ABSTRACT
A wide variety of industries make use of cost-effective foam control as a process aid and to provide a vital function in their products. Foam control process aids are the largest single category of process aids used in the chemical industry. This chapter reviews the nature of foams and emulsions, and the mechanisms by which antifoams and demulsifiers are believed to function in both aqueous and nonaqueous applications. It discusses selected foam and emulsion control problems that involve the use of silicone polymers and copolymers. Polydimethlysiloxane, some silicone polyoxyalkylene copolymers, and fluorosilicone polymers have lower surface tensions than hydrocarbon liquids and are surface active at the hydrocarbon-air interface. Polymers that are marginally soluble in the continuous phase can be profoamers below their solubility limit. Fluorosilicones have been used in numerous nonaqueous foam control and demulsification applications. The mechanisms of demulsification have been far less studied than for antifoams, but they are thought to involve the following processes.
