Aqueous film forming foam (AFFF) is the state-of-the-art technology available today to fight against liquid fuel pool fires. AFFFs traditionally contain perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). These chemicals have the strongest chemical (carbon-fluorine) bonds and are considered persistent, bio-accumulative and toxic (PBT) substances. PFOS/PFOS chemicals have leached into groundwater and were detected around the world in the food chain, drinking water, animals and even in human blood. Due to their ubiquitous presence in the environment and the increasing concern of their toxicological effects, efforts have been focused on reducing exposure to these chemicals. Recently, Environmental Protection Agency, EPA has regulated the chemical industry for the complete elimination of PFOA and PFOS chemicals. The regulation on PFOA/PFOS chemicals is directly affected by the AFFF industry. Therefore, we and others working on environmentally acceptable alternatives such as fluorine-free siloxane-based AFFF, for use on militarily relevant fuels, to meet the performance requirements of the MIL-F-24385F standard.
The primary objective of this technology is to develop a fluorine-free surfactant formulation for use in AFFF. Specific surfactants have been identified, and their use in AFFF is under evaluation that could potentially replace fluorinated surfactants. The fire suppression performance of the proposed siloxanes will be tested to meet the performance requirements of the MIL-F-24385F standard. The testing will include lab-scale physical properties measurement and fire-test, evaluation of 28-ft² fire performance, spreading coefficient, aquatic toxicity, chemical oxygen demand (COD) and bio-persistency.
The new material system containing specific functional groups to reduce surface energy and the ability to form a stable water film over the flammable fluids were synthesized, and their foam foaming abilities were measured. The resulting fluorine free surfactants have the potential to create a stable foam layer on top of liquid hydrocarbon fuels and act as a barrier for combustible liquids from supplying fuel vapor to the fire.