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Sunday
Sep012013

Foam 103 - Foam Properties

            The history of Foam concentrates and their creation, evolution, and endpoint into the current “green Foams” is an important field of study towards understanding. If the modern responder knows the “history” of Foam concentrate evolution, he/she is better equipped to appreciate how the industry developed, and where it may be going in the future. As an example, see the article (Cool Environmental Solution). The properties of modern Foam concentrate yield many ideas for innovation, the above article demonstrating this principle.

The basic five (5) properties required for class “B” flammable liquid Foam concentrate that were defined in last month’s Foam 102 developed into five (5) different categories of Foam concentrate. These types or categories of Foam concentrate, evolved from “organics” to “syn-dets” and finally into the “Green” Foams we see today. Their individual properties are listed in chart form for easy examination. They are as follows;

1] Protein Foam Concentrate

2] Fluor-protein Foam Concentrate

3] AFFF Concentrate

4] FFFP Foam Concentrate

5] AR-AFFF Concentrate

Protein Foam Concentrate - 

Protein Foam concentrate was originally created from the natural "soaping" action observed from the addition of organic ground up high protein components of animal renderings. The most common was ground powder made from pulverized horse and cattle hoofs. These materials when liquefied, aerated, educted, aspirated, and applied to flammable liquid fires showed high success in extinguishing these types of fires before WWII. These Foam concentrates were relatively inexpensive and provided dependable performance when used within their limitations. Protein Foam lacked fuel tolerance so gentle surface application to the surface was needed. They required more mechanical agitation and were much more beneficial when used with air-aspirating nozzles. Finally; their rigid and stable molecular structure reduced their knockdown speed, but increased their heat resistance and vapor suppression.

Fluoro-Protein Foam Concentrate -

            At the beginning of WWII, a faster response for fire suppression was needed to protect the USN. The addition of special fluoro-chemical surfactants to protein Foam concentrate corrected this issue. These surfactants reduced surface tension and increased fluid movement knockdown. These surfactants also improved fuel tolerance characteristics reducing the need for gentle application as seen in the protein Foam concentrates. This addition allowed the industry to perfect subsurface application techniques.

AFFF-Aqueous Film Forming Foam Concentrate

AFFF evolvement continued through history primarily for the military to have a tool that could accomplish a very fast flammable fire knockdown for small fire areas. Accidental fires aboard ship and at air-bases were claiming a substantial amount of casualties in both equipment and manpower. Shallow fires involving fuel and diesel do not produce the same level of heat as hydrocarbon tank fires. Increasing rapid knockdown sacrificed long term stability and vapor suppression characteristics. By the addition of synthetic detergents to the fluorochemicals successfully created this unique aqueous film. The film itself is a layer of Foam solution that reduces surface tension thus increasing rapid spreading across the fuels surface.

FFFP-Film Forming Fluoro-Protein Foam Concentrate

This next evolution was an attempt to combine the characteristics of Protein Foam concentrates with the speed of the aqueous films. Unfortunately, the result was that while the heat resistance and fuel tolerance properties increased, the rate of knockdown decreased. They perform much like the AFFF without any synthetic detergents in the molecule. Their composition is much more akin to the Fluoro-protein Foam concentrates but with a much more sophisticated fluorochemical package that produces the filming formation on the surface of hydrocarbon fuels. These Foam concentrates possess strengths in different areas while “flattening out” the advantages of each of its components.

AR-AFFF-Alcohol Resistant Aqueous Film Forming Foam Concentrate -

Finally; as fuels and the chemical industry advanced, alcohol was introduced into the equation for environmental protection reasons. This new issue had a marked affect on the Foam concentrate industry. Suddenly, large amounts of “solvent” based, or alcohol materials were being used that resisted fire suppression from all previous Foam concentrates. In 1975 the first AR-AFFF consisted of synthetic stabilizers, Foaming agents, fluorochemicals, and synthetic polymers. This combination afforded a mucous membrane to form between the Foam blanket and the fuels surface. The formation of this layer prevents the chemical characteristics of an alcohol (or polar) fuel from destroying the finished Foam blanket. AR-AFFF is today’s most versatile type of Foam concentrate affording good or excellent tolerance for both hydrocarbon and alcohol type fires.

The hazardous materials responder that has a strong understanding of the various advantages of all these Foam concentrate types is better equipped to choose which option will perform the best to mitigate various environmental hazards in the safest possible manner.

                                            Haz Mat Mike

     

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