Foam and defoaming agent
I. overview of bubbles
Foam consists of three components (gas, liquid, surfactant) and two phases (gas and liquid)
Causes of bubbles:
Produced by agitation
Stable foams are formed from surfactants, such as nonionic, anionic surfactants, proteins, fine solid particles, etc.
But most of the time it's a problem:
Reduces pumping efficiency
Adiabatic, difficult to control temperature
Reduce container capacity
Prevention of distillation
Increase filling time
How to eliminate and suppress bubbles?
Foam is a natural product of many manufacturing processes, for which effective foam control is essential, otherwise many processes are severely limited or do not work at all. General methods to control foam include:
Change the temperature
Reduce the pressure
Adjust stirring speed, etc
Silicone defoaming agent
Non - silicon defoaming agent
Classification of foam control
Defoaming: removing existing bubbles
Bubble suppression: inhibiting the formation of bubbles
Degassing: gathering fine bubbles into large ones
How to choose defoaming agent?
Generally speaking, effective defoaming agents must meet the following conditions:
• it must have a higher surface activity than the foaming surfactant, that is, it must have a lower surface tension.
• easy dispersion in the system
• it must be insoluble (at least partially insoluble) in a foaming medium, or it will act on its own as a surfactant, thus stabilizing the foam.
• the droplet size of the defoamer should be within the foam thickness range.
• chemical inertia
• no residue or odor