FIRE-FIGHTING FOAM INDUSTRY
Fluorochemicals have long been used as key components of certain fire extinguishing foam agents typically used for fires of flammable or combustible liquids, such as gasoline and oil. Categorized as Class B fires, they can be extinguished by several different types of Class B foam agents or concentrates: synthetic foam agents, like AFFF (Aqueous Film Forming Foam) and AR-AFFF (Alcohol-Resistant AFFF), and protein-based foam agents, such as FP (Fluoroprotein), FFFP (Film Forming Fluoroprotein), and AR-FFFP (Alcohol-Resistant FFFP). Whether synthetic or protein-based, the foam is generated from a diluted solution of foam concentrate and water. Three or six parts of the concentrate are typically diluted with 97 or 94 parts of water (3% and 6%), although highly concentrated foam agents designed to be diluted with 99 parts of water (1%) have also become recently available.
Synthetic foam agents typically contain three key components: hydrocarbon surfactants, fluorosurfactants, and solvents. Surfactants reduce the surface tension of the foaming solution (low surface tension is responsible for foaming). Fluorochemicals, especially fluorosurfactants, are essential components of film forming foam agents, such as AFFF. This class of fire-fighting foams, as the name implies, is capable of spontaneously spreading and forming an aqueous film on low surface tension, flammable hydrocarbons. This film (formed with the solution drained from the foam) acts as a fuel vapor barrier, enhancing the overall fire extinguishing effectiveness of the foam. The spontaneous spreading and forming of an AFFF’s aqueous film is due mainly to the very low surface tension caused by the fluorosurfactants (15-20 dyne/cm). This low surface tension is coupled with a low interfacial tension (1-5 dyne/cm) caused by hydrocarbon surfactants; together, these characteristics allow the AFFF solution to spread spontaneously on liquid hydrocarbons and fuels.
In addition to the fluorosurfactants, fluorochemical-based foam stabilizers, such as Dynax’s DX5011 and DX5044, are also used in formulating Class B foam agents designed for extinguishing fires of water-miscible, polar solvents such as alcohols and ketones. These foam concentrates are collectively known alcohol-resistant foam agents (AR-AFFF and AR-FFFP). The fluorochemical foam stabilizer stabilizes the foam that in its absence would break up in contact with the polar solvent.