Enhanced Thermal Stability and Resistance Properties of Gel‐Stabilized Foam for Inhibiting Coal Spontaneous Combustion

ABSTRACT To overcome the limited thermal stability and fire retardancy of single‐component organic foam and gel for coal spontaneous combustion prevention, this study developed a novel gel foam via a “gel‐organic foam composite” approach. Comparative tests with conventional materials showed that the gel foam maintained 86.47% water retention at 60°C and over 50% at 180°C, outperforming organic foam and gel. Its layered‐porous structure, formed by gel‐foam synergy, controlled volatile release and reinforced the char layer. Fire retardancy tests revealed a 20°C higher cross‐point temperature and a 16% relative enhancement in CO 2 suppression rate at 150°C versus organic foam. Programmed heating and field tests confirmed rapid cooling of a 900°C coal sample to below 100°C within 600 s without re‐ignition, whereas single‐component materials re‐ignited. The gel foam achieves “physical encapsulation–chemical stabilization–oxidation inhibition” synergy: CMC‐Na and NaCit cross‐linking form a dense network that adsorbs free radicals on foam walls, inhibits active coal functional groups (OH, CH 2 ), and reduces oxygen contact area by 40%. This structurally optimized material offers broad potential for long‐term fire suppression in complex coal fire zones.