Study on the effects of silica aerogels on the performance of APG0810/PMH fluorine-free foam

Perfluorooctane sulfonate (PFOS) serves as the primary ingredient in aqueous film-forming foam used for extinguishing fires. Nevertheless, PFOS is recognized as a persistent organic pollutant. Therefore, creating environmentally friendly fluorine-free foam (FFF) extinguishing agents is of great significance. To formulate fluorine-free foam extinguishing agents, a hydrocarbon surfactant (APG0810) and silicone surfactant (PMH) were chosen as the main components. To enhance the foam stability, silica aerogel was added as a foam stabiliser. The interaction mechanism between silica aerogels and surfactants was demonstrated. The results show that when the amount of silica aerogel added was 3 wt% (PA-4), the 25% drainage time was 203 s. The surface tension was slightly reduced to 23.79 mN/m, the viscosity was 3.2 mPa⋅s, and the foam height was 181 mm. The results of foam coarsening revealed that small-sized bubbles were evenly distributed. The foam solution with silica aerogel added had better stability at high temperatures. After heating for 3000 s, the residual foam of PA-4 still remained at 1/3 of the initial foam volume. Small-scale fire extinguishing experiments with 3 L of gasoline were carried out, and the fire was completely extinguished within 72 s.