What Causes Foam?
Foam is a mass of bubbles formed when gases, (usually air) are dispersed into a liquid, and stabilised. Rarely does a pure liquid produce foam, mostly a surface active agent or surfactant is what causes foam, except in hydrocarbon systems mixed isomers are responsible.
Foam is inherently unstable and will collapse to a liquid without an external energy source. Absorption of a surfactant by the liquid opposes this collapse by increasing the surface tension of the liquid. Almost any liquid can foam with the correct choice of surfactant, and gas infusion. A higher viscosity liquid will also increase the stability of foam.
Antifoams treat foam in one of two ways. They either displace the foam stabiliser from the bubble walls and reduce the surface tension, and/or they locally burst the bubbles. Foam stabiliser replacement depends on the foam liquid and antifoam surface tension. It is important that the surface tension of the antifoam is less than that of the foam.
Efficient dispersion of the antifoam is critical to allow the surface-active material to reach most foam sites. In emulsion systems it is the use of fine particle size fillers such as fumed silica and magnesia that both aid in the dispersion of the surface active agent and also help to burst the foam bubbles.
Antifoam efficiency is a measure of two things:
1) the speed at which a given amount of antifoam can knock down a standard foam solution and
2) how long it will continue to perform.
The long-term performance is measured by the reformation of foam over a period of time. There is a wide variance in the antifoam efficiency of different silicone antifoams just as there is a wide variance in price. Often an antifoam with the same active solids and a higher dollar per kilogram price is cheaper to use than a product costing less per kilogram, as the amount needed is significantly less overall.
Foam is a mass of bubbles formed when gases (usually air) are dispersed into a liquid and stabilised. Rarely does a pure liquid produce foam mostly a surface-active agent or surfactant is what causes foam, except in hydrocarbon systems mixed isomers are responsible.
Types Of Antifoams
There are 2 main types of antifoams, silicone based and mineral oil based.
Mineral oil based are typically used in the paint, ink, and coatings industries so as to avoid spotting or surface defects due to the low surface tension of silicone.
Silicone antifoams are generally much more efficient.
Antifoams for Oil Based Systems
- The best is a silicone concentrate compound such as CAF1000C, which contains additives to markedly improve efficiency over straight silicone fluid.
- If using a silicone fluid, selection of the right material is determined by whether fast knockdown or long-term antifoam characteristics are required.
- Typically, the lower the viscosity of the silicone fluid the faster the foam knock-down, and the higher the viscosity the better the long term defoaming property. A good compromise is CF12.5K (12,500 cSt silicone fluid).
Antifoams for Water Based Systems
- Silicone antifoams are normally classified into either food grade or industrial grade antifoams. They are normally supplied in 10, 20, and 30% emulsions ready for use or 100% concentrates that need to be emulsified.
- Water based antifoams can be diluted in water to aid in dispersion in some applications however need to be constantly agitated once diluted to mitigate stability issues, please see ‘Dilution of Antifoams Emulsion’ below for more information.
Industrial Grade Antifoams
- These usually have two major modes of action in combination. The first is fast know down to remove foam present at the time of addition. The second gives long term defoam efficiency to stop the reforming of foam.
- Products designed to give both properties include CAF100, CAF200, and CAF300.
- Another alternative is a low cost per kg product that is dosed as required in such applications as waste water. A recommended product is CAF505.
- If non-silicone antifoams are required, we recommend CNS890, CNS7100. For dry mixtures such as wash powders CAF1020P can be added before dissolving.
Food Grade Antifoams
- Flexichem’s silicone food grade antifoams are formulated with food grade silicone fluid and food approved ingredients. The equipment used to manufacture the antifoam is sterilised before use and all batches are tested for microorganisms such as bacteria and microspore to ensure the batch meets with health standards. All containers are food approved and sterile before use.
- All Flexichem food grade antifoams CFA110, CFA210, CFA310 and CFA1000, are produced according to the highest food safety standards and TDS’s, C of A’s and food status statements are available upon request.
- An alternative when a solid mixture needs a defoamer present before dissolving is the powder CFA1020P.
- Food Grade Status:
- All Flexichem silicone Food grade Products are manufactured free of genetically modified food components, according to the raw material documentation supplied to Flexichem.
- Flexichem can supply PIF, Allergen, GMO and Kosher statements on request and is actively working towards HACCP Accreditation.
Dilution Of Antifoam Emulsions
With the exception of antifoam compounds CAF1000C, and CFA1000C, Flexichem antifoam emulsions are intended for use as supplied. Some users however may desire to utilise diluted versions because of the small amounts required.
It should be noted that antifoam emulsions such as CAF505, CAF100, CAF200, and CAF300 are not designed to be dilution-stable as they are typical silicone release emulsions that are intentionally designed to break when diluted with water.
This feature is necessary for an antifoam emulsion as if it were too stable it would be a far less efficient defoamer and not be surface active where the foam is. When an antifoam emulsion is added to a foaming system the silicone emulsion breaks. This liberates a silicone compound which is the main defoaming agent. The major function of the emulsion is to enable the silicone compound to be thoroughly dispersed throughout the solution to be defoamed.
This feature of silicone antifoam emulsions means that although antifoam emulsions may separate when diluted they can readily be redispersed with mild agitation prior to use and continue to function as normal. It is recommended that mild agitation is maintained prior to or while using the diluted product in order to assure uniform consistency.
It is possible to produce a dilution stable antifoam for more information contact Flexichem’s technical staff.
|CAF505||Silicone Antifoam||10% Active industrial silicone antifoam||Low Cost General Purpose/Waste water|
|CAF100||Silicone Antifoam||10% Active industrial silicone antifoam||General purpose|
|CAF200||Silicone Antifoam||20% Active industrial silicone antifoam||General purpose|
|CAF300||Silicone Antifoam||30% Active industrial silicone antifoam||General purpose|
|CFA110||Silicone Antifoam||10% active food grade silicone antifoam||Food grade applications|
|CFA210||Silicone Antifoam||20% Active food grade silicone antifoam||Food grade applications|
|CFA310||Silicone Antifoam||30% Active food grade silicone antifoam||Food grade applications|
|CFA1020P||Silicone Antifoam||20% active food grade antifoam powder|
|CFA1000C||Silicone A/F Compound||100% Food silicone AF compound||Non aqueous food grade applications|
|CAF1000C||Silicone A/F Compound||100% Active industrial antifoam||Non aqueous and antifoam manufacturing|
|CNS7100||Non-Silicone Antifoam||100% Active industrial antifoam||Used in paints, inks, adhesives, waste water, latex, etc.|
|CNS7100F||Non-Silicone Antifoam||100% Active food contact antifoam||Food contact inks and adhesives, etc.|
|CNS890||Non-Silicone Antifoam||100% Active industrial antifoam||Paint, waste water|
|HSA705||Non-Silicone Antifoam||100% Active food grade antifoam||Processing, waste water, fast knockdown|