Per- and polyfluoroalkyl substance (PFAS) surfactants are powerful additives in aqueous film forming foams to extinguish flammable liquids, but they present serious environmental and health threats. Alternative PFAS-free formulations are on the market, but these alternatives still do not meet the firefighting requirements set by the MilSpec MIL-PRF-24385. The objective of this project is threefold:
- To improve firefighting properties of PFAS-free foaming formulations by addition of clay nanoparticles and water soluble polymers. These materials are designed to adjust the draining and flow of the foam.
- To establish a relationship between the fire extinguishing capabilities and the nature of nanoparticles, polymers and surfactants. This will enable the project team to optimize draining kinetics and rheology for firefighting performance.
- To assess the environmental and health impact of new formulations, which will allow the project team to produce safe and environmentally-friendly foams.
In the development of PFAS-free foams, alternative surfactants are often developed that mimic the spreading behavior of PFAS surfactants. This is known to be very challenging. In previous research to develop a PFAS-free formulation for five liter extinguishers, the Netherlands Organization for Applied Scientific Research’s scientists followed a different approach, which focused more on improving the draining and flow of the foam layer. A combination of clay nanoparticles and polymers was used as additives in foaming formulations. Although the additives have little influence on surface and interfacial tension, their use strongly improved fire extinguishing performance. The additives enhanced both the foam stability, spreading, and flow. A similar approach is suggested for this effort, with some modifications to address the MilSpec requirements. For example, the concentration of some components used in the five liter extinguishers are too high to be used in the 3% and 6% concentrates needed for large fires. Therefore, the original formulation will be redesigned. The composition of the nano-clay particles and polymers and their concentrations will be varied according to design of experiments to tune their interaction with each other and the other components in the extinguishing liquid. The rheology of the liquids and foams will be studied and correlated with firefighting performance on a small scale. This will provide an understanding of the foam behavior to effectively extinguish fires, while minimizing the concentration of nanoparticles and polymers to enable the use of 3% and 6% concentrates. The most favorable additives will be combined with state of the art surfactants. For promising combinations, the adherence to firefighting requirements in MIL-PRF-24385 will be evaluated and the formulations optimized. The health safety and environmental aspects will be assessed in two stages. During the early research phase, the most promising clay nanoparticles will be assessed with a qualitative evaluation method to guide the development. In a later stage, the developed foam formulations will be assessed and compared with the conventional PFAS-foam in a quantitative Life Cycle Assessment.
A successful project will generate new, effective, environmentally-friendly and safe additives that can enhance firefighting performance. Foams with these additives will, in combination with state of the art surfactants, comply with the fire extinguishing requirements of MIL-PRF-24385. The development will lead to reduction of the firefighters health risks and will strongly reduce the environmental impact of spills.