The Department of Defense is in need of a fluorine-free aqueous film forming foam (AFFF) fire suppression solution due to the current/pre-existing AFFF technology containing fluorine products that are toxic to both the environment and military personnel. In this project, Materials Modification, Inc. (MMI) investigated and developed a fluorine-free ionic liquid for use in AFFF solutions that can potentially meet the performance and toxicity levels of the MIL-F-24385F standard.
Ionic liquids are non-toxic and can be tailored to various applications based on synthesis procedures and their functional groups. MMI developed a low surface tension, fire quenching, and fluorine-free ionic liquid that produced stable foams when combined with trisiloxane surfactants. MMI assessed the feasibility of using ionic liquid (IL) chemicals for AFFF applications through lab-scale benchtop trials using controlled fire environments. The developed AFFF solution was also be evaluated under standardized conditions according to the MIL-F-24385F standard for fire suppression and toxicity.
Novel ionic liquid surfactants were synthesized and tested for their AFFF capabilities. Ionic liquid surfactants have the potential to produce AFFF solutions when mixed with trisiloxane surfactants. Ionic liquids enhanced the foam spreading and fire extinction properties of trisiloxane surfactants, possibly through the Marangoni effect. The new ionic liquid surfactant-based formulations were able to quench the benchtop gasoline fuel pool fires <30 seconds. Further optimization of ionic liquid/trisiloxane formulations could yield a fluorine-free formulation that can replace current AFFF.
Ionic liquid-based firefighting foam system developed in this effort can be used to rapidly quench fires as well as provide an insulating coating on extinguished surfaces for quick recovery action. This system will be particularly useful for military application for recovery of sensitive equipment, materials and will also be useful in the commercial and industrial sector (firefighters, hazmat personnel, and first responders). (Project Completion - 2022)