Abstract: This study fully leverages the excellent foaming performance of hydrocarbon surfactants and the superior spreading ability of organosilicon surfactants. Guided by the carbon-silicon synergistic effect, we developed a novel anionic, fluorine-free foam fire extinguishing agent, composed of α-olefin sulfonate (AOS) and polyether-modified heptamethyltrisiloxane (SILWET L-77) as surfactants, with xanthan gum (XG) as a key functional component. We further investigated the foam formulation design, foam performance, and fire extinguishing efficacy. The results indicate that the optimal formula was AOS with a mass fraction of 2.75%, SILWET L-77 with a mass fraction of 1%, and XG with a mass fraction of 0.275%. Tests over a wide temperature range (20~80 °C) showed that both foam viscosity and surface tension decrease exponentially with increasing temperature (R²>0.98). In a 0.25 m² standard oil pan fire test, the new fluorine-free foam exhibited an average foaming ratio of 6.1, an average 90% fire control time of 34.3 s, an average extinguishing time of 82 s, an average burn-back resistance of 401 s, and an average maximum cooling rate of -8.67 °C/s at the monitoring point. These results provide valuable guidance for the formulation and performance optimization of novel fluorine-free foam fire extinguishing agents.

Key words: fluorine-free foam extinguishing agents, surfactants, formulation optimization, foam performance, fire extinguishing tests