Foam Controller: Classification, Uses, and Mechanism of Action

Classification of Foam Controller

A foam controller is generally a liquid formulation and can be categorized into three main types: mineral oil-based, silicone-based, and polyether-based. A mineral oil-based foam controller typically consists of a carrier and an active agent. The carrier is a low surface tension substance, responsible for carrying and diluting, with common carriers being water, fatty alcohol, etc. The active agent's role is to suppress and eliminate foam, and common agents include wax, fatty amide, and fatty acid. A silicone-based foam controller usually includes polydimethylsiloxane and similar compounds. Silicone-based foam controller has poor solubility but features fast foam-breaking action and good foam suppression at room temperature. However, at high temperatures, it may undergo stratification, with slower foam-breaking and reduced foam suppression. A polyether-based foam controller includes polyoxypropylene oxide ethylene glycol ether. Polyether-based foam controller is known for long-lasting foam suppression, fast foam-breaking speed, and excellent thermal stability. For example, a foam controller is often used in the production of fruit and vegetable juice, soy products, and sugar refining.

Use of Foam Controller

A foam controller is primarily applied in processes involving printed circuit boards (PCBs), chemicals, electroplating, textile printing and dyeing, papermaking, pharmaceuticals, water-based inks, ceramic cutting, steel plate cleaning, aluminum processing, wastewater treatment, and various industrial water systems for foam suppression and control.

Mechanism of Action of Foam Controller

Reduction of Local Surface Tension Leading to Foam Rupture

This mechanism involves sprinkling high-grade alcohol or plant oil onto foam. When this substance dissolves into the foam liquid, it significantly lowers the local surface tension. Since this substance generally has low solubility in water, the reduction in surface tension is limited to the foam's local area, while the surface tension surrounding the foam remains almost unchanged. The lowered surface tension is strongly pulled and extended in all directions, ultimately causing the foam to break.

Destruction of Film Elasticity Leading to Foam Rupture

When a foam controller is added to the foam system, it spreads across the gas-liquid interface, preventing the surface-active agent responsible for stabilizing the foam from restoring the elasticity of the foam membrane.

Promotion of Liquid Drainage from the Film, Leading to Foam Rupture

The rate at which foam drains reflects its stability. Adding a substance that accelerates foam drainage can also serve as a foam controller, breaking down the foam.

Addition of Hydrophobic Solid Particles Leading to Foam Rupture

Hydrophobic solid particles on the surface of bubbles attract the hydrophobic end of the surface-active agent, making the hydrophobic particles become hydrophilic and enter the water phase, thereby facilitating foam control.