The objective of this project was to improve the fire-fighting efficiency of the siloxane surfactants based foam formulations toward meeting the performance of per- and polyfluorinated alkyl substances (PFAS) containing Aqueous Film Forming Foam (AFFF) products.
In this project, low surface tension, fire quenching, and fluorine-free siloxane surfactants were developed. The siloxane surfactants produced stable foams when combined with selective additives. The feasibility of using siloxane surfactants for AFFF applications was assessed through benchtop trials using gasoline pool fire. Selective formulations were evaluated for large scale Mil-spec 28ft2 fire testing and aquatic toxicity.
Numerous commercial and proprietary siloxane surfactants (prepared in-house) were tested and the best performing surfactants were selected based on their firefighting performance and foam stability. It was determined that low surface tension of the surfactant alone does not guarantee foam formation or foam stability. The foam stability can be significantly improved with selective additives. The best performing foam formulations were selected from benchtop pool fire testing studies for 28ft2 gasoline pool fire testing. The firefighting performance of siloxane surfactants was encouraging (extinction time 38 seconds versus 30 seconds for AFFF @ 2 gal/min with mil-spec aspirated nozzle) and has the potential as a “drop-in” replacement for AFFF.
PFAS-free firefighting foams have considerable financial, socio-economic, public health, and environmental advantages over bio-accumulative and toxic fluorochemical-based AFFFs. The new formulations developed in this effort will comply with environmental regulations while meeting the military-standard requirements. The initiative will eliminate the use of traditional AFFF formulations and provide the operational capabilities to military and first responders with a fluorine-free Class B foams in fighting against liquid fuels.