Technical Article

Defoamer/Antifoam Mechanism Introduction

Defoamer/Antifoam Mechanism Introduction


 
 
Foam is a 3-component (gas, liquid and surfactant), 2-phase system (gas and liquid) 
 
Reason to cause foam:
  • Created by agitation
  • Stabilized by surface active agents such as nonionic & anionic surfactant, proteins, fine particulate solids, etc.
 
                                   Not stable system                                                                Metastable system
 
Sometimes bubbles are a good thing…

But most of time bubbles will bring troubles:
  • Process fluctuations
  • Poor washing, filtration and drying
  • Reduced pumping efficiency
  • Thermal insulation – poor temperature control
  • Floatation of solids
  • Reducing vessel capacity
  • Preventing distillations
  • Increasing packaging (bottling) times
  • ....etc
Foaming is inherent to many manufacturing processes, for which effective foam control is a ‘must have’ because without it many processes are seriously restricted or do not function at all
 
Physical control  
  • Temperature 
  • Pressure        
  • Agitation     
Chemical Control 
  • Silicones      
  • Organics      
 
What is Foam Control ?
  • DE-foaming = knock-down of existing foam
  • ANTI-foaming = prevention of foam formation
  • De-aeration = coalescence of (micro)bubbles
 
In general, effective defoamers must meet the following conditions:
• Must have a higher surface activity than a foamed surfactant which means it must have a lower surface tension.
• Easy to disperse in the system
• It must be insoluble (at least partially insoluble) in the foaming medium, otherwise it will act as a surfactant and will stabilize the foam.
• The droplet size of the defoamer should be within the thickness of the thin layer of foam.
• Chemically inert
• No residue or smell
 
Antifoam requirements-general
  • Rapid knockdown (for ‘spot’ dosing).
  • Long durability (fewer dosing points, lower consumption).
  • Good de-aeration
  • Low viscosity (ease of pumping & dosing)
  • Stability
    • of the product as supplied (for storage)
    • of the product as dispersed into the foamant (for effectiveness)
  • High activity (low dosing = minimal residues)
  • Performant in non-ionic, cationic & anionic surfactants
  • Effective at low & high temperatures (Cloud Point effect)
  • Effective at low & high pH
  • Effective in high salt concentrations
  • etc...
  • and competitive cost-performance
 
Mechanism of Defoaming:

Silicone Vs. Organic Antifoam

 

Innovate a defoam/antifoam is an art of balance
  • mechanism makes a defoam must be not compatible with foam
  • better performance, worse compatibility
  • better compatibility, worse performance
  • Appropriate defoam is a balanced product
 
Many surfactant based chemicals have the property of foam which brings a big trouble to the suppliers. But most of antifoams in the market with good antifoam property can’t have good enough compatibility in this kind of aqueous system, sometimes storage or worse performance problem. Our team invested and innovated new products to fulfill our customers’ different these kinds of requests.


 

Product introduction
  • Resist temperature range 0~90︒C
  • Resist pH range1~14
  • Good compatibility with anionic and nonionic aqueous system

*The photos of solutions were taken after 90 days storage.
 
 

Shanghai ChemGeek Chemical Co., Ltd.
Mr. Ken Yang

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