A study on a Janus-type composite solidified foam and its characteristics for preventing and controlling spontaneous combustion of coal

To solve the problem of poor effect of plugging air leakage in the prevention and control of coal spontaneous combustion by traditional inorganic solidified foam, Janus-type composite solidified foam (JCSF) was proposed in this study. An ultra-stable aqueous foam (UAF) was synthesized via the modification of the gas-liquid interface by forming a “Janus bilayer” of hydrophobic nano-silica and hydrophilic polyvinyl alcohol. Different techniques were used to study the stability of UAF. In addition, by using non-combustible inorganic materials such as cement and fly ash as the matrix and organic materials as the reinforcement, JCSF was synthesized by the prefabricated foam method, and its formulation was optimized by the response surface methodology. The stability test of UAF indicated that the “Janus bilayer” could effectively inhibit the Ostwald ripening, continuous coalescence, and drainage of the foam. The air leakage plugging efficiency, flame retardancy, fire extinguishing, and stacking characteristics showed that JCSF combined the advantages of traditional inorganic solidified foams and reactive polymer foams. It also showed a higher air leakage plugging efficiency, lower heat production, excellent fire prevention and extinguishing, and strong accumulation capacity.