Preparation of a Viscous Hydrogel and Research on its Flame-Retardant Properties

The spontaneous combustion of coal restricts the development of green coal mining. Hydrogels are often used to block air leaks and prevent the spontaneous combustion of coal, but traditional hydrogels suffer from poor adhesion and mobility; therefore, to prevent the spontaneous combustion of coal and improve the utilization rate of hydrogels, this study proposes a new type of fire-extinguishing viscous hydrogel, polyacrylic acid-sodium alginate-tannic acid (PAA-SA-TA). The viscosity, air plugging and blocking characteristics, adhesion mechanism, air plugging efficiency, and thermal stability of the PAA-SA-TA hydrogel were analyzed. The results showed that the viscosity of the PAA-SA-TA hydrogel was about 70% higher, and the blocking efficiency and blocking rate were 42.90% and 39.53% higher than those of a poly acrylic acid (PAA) hydrogel, respectively. In addition, the fire extinguishing tests showed that compared with PAA and polyacrylic acid-tannic acid (PAA-TA) hydrogels, PAA-SA-TA evenly covered the surface of the burning coal body, densely wrapped the coal body, filled the cracks, and extinguished the fire without re-ignition. This study provides a new viscous hydrogel for the prevention and control of the spontaneous combustion of coal in mines.