1960s revolutionised the firefighting industry with the development of the aqueous film-forming foams (AFFF) used to suppress fires of flammable liquids

The 1960s revolutionised the firefighting industry with the development of the aqueous film-forming foams (AFFF) used to suppress fires of flammable liquids. Until a decade ago, AFFFs were almost the only foams used for emergencies at airports, military bases, refineries, oil rigs and by fire and rescue d services.
Unfortunately, the per- and poly-fluoroalkyl substances (PFAS) present in the AFFFs are non-biodegradable, persistent and toxic, negativily impacting human health and the environment. Fluorine-free firefighting foams (FFF) are undergoing rapid development as an alternative to the AFFF concentrates. However, they are currently not as efficient as AFFF.
This research aims to identify and study the fundamental properties that must be improved for FFF to be as effective as AFFF.
We investigate the fire extinguishing processes that come to pass during application of FFF and AFFF to fires of flammable liquids. We study the interaction of the foam with the fuel, when the foam impacts the fuel surface.
At the point of impact, the foam mixes with the fuel. This phenomenon is called fuel pick-up, and it is an very important characteristic of firefighting foams because high values of fuel pick up can cause the saturation of the foam with fuel and propagation of the fire.
The extent of pick-up depends on the velocity and density of the foam stream, the rheological properties of foams, and the chemistry of the surfactants used to prepare the foam concentrate. The understanding of the foam non-Newtonian rheology, elasticity and yield stress is essential to predict its fuel pick-up, and it is the objective of the first part of the project.
In the second part of the project, we will investigate how FFF and AFFF differ in their interaction with the fuel. Results from the preliminary investigations suggest substantial disparities in the flammability between foam-fuel mixtures for FFF and AFFF. While AFFFs appear to be more effective emulsifiers than FFFs, and, therefore, pick up more fuel, the AFFF-fuel mixtures are less flammable than those of FFF-fuel.
A better understanding of the extinguishing processes enables more focused research into improved FFF formulations. The research may enable improved laboratory scale testing of foams. This would reduce the cost and time for development. Phasing out the use of PFAS in fire fighting foams as rapidly as possible has obvious environmental benefits.