Aqueous Film Forming Foam (AFFF) is the method of firefighting liquid fuel fires discovered in the 1960s, developed in the 1970's and employed by domestic and military facilities handling flammable liquids. It extinguishes fires by forming a film between the fuel and air, preventing combustion from occurring. It also inhibits vaporization of more fuel by creating a thermal barrier that limits fuel from evaporating. AFFF typically used as a solution of either 3 weight percent (wt%) or 6 wt% surfactant formulation that is foamed as it is sprayed out of the hose nozzle. The surfactant contributes to the effectiveness of AFFF because of its ability to reduce the surface tension of the film and allow foams to spread better across the entire fuel pool. For several decades the most prominent surfactants were made with fluorinated compounds, particularly perfluorooctane sulfonate, or perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). PFOSs are environmentally toxic and persistent, and they were removed from use in AFFFs. Currently, the alternative surfactant used in AFFF is a six atom long perfluorinated compound commonly referred to as C6. Concerns over the persistent, bioaccumulative, and toxic nature of C6 has created a demand for a surfactant that avoids the use of per and polyfluorinated alkyl substances (PFAS) altogether. This project will address the SERDP’s objective of Statement of Need by developing a novel extinguishing foams based on functionalized hollow microspheres which are nontoxic and potentially effective at extinguishing fuel fires for use in Department of Defense Class B (flammable liquid) fire-suppression operations by MIL-F-24385F specifications.
This project will build upon the previous research work on PFAS free foam based on siloxane surfactants. The work on siloxane surfactants clearly demonstrated that foam stabilizers can enhance their fire-fighting efficiency. However, further optimization of the composition and appropriate additive will be required to better the performance of polyfluorinated AFFF formulations. In this effort, specific additives will be judiciously selected as additives for previously developed siloxane surfactants form formulations.
The continued use of polyfluorinated fire-fighting foams is not environmentally and commercially sustainable due to the growing awareness on the social impact and enormous cost expected from cleaning the contaminated environment. The safe alternate to polyfluorinated chemicals will reduce the water and soil contamination and will help in improving the human health caused by the AFFF used in firefighting.