Preparation and Characterization of Chitosan Grafting Hydrogel for Mine-Fire Fighting.

Mine fires are one of the primary natural disasters in coal production. The majority of mine fires are caused by the spontaneous combustion of coal. To reduce the risk of spontaneous combustion of coal, a new fire prevention and extinguishing hydrogel has been developed. Poly(acrylic acid--methacrylamide) (P(AA--MAA)) and chitosan-grafted poly(acrylic acid--methacrylamide) (CTS--P(AA--MAA)) were prepared by aqueous solution polymerization, and their characteristics have been studied by scanning electron microscopy and Fourier transform infrared spectroscopy. The swelling ability and water retention of the hydrogels were also tested and compared. The experimental results showed that the grafting of chitosan can improve the water-absorbing ability of the hydrogel in acidic solution and deionized water and enhance the water retention of the hydrogel. The thermogravimetric experiments of the mixture of the hydrogel and coal showed that the thermal stability of the mixture was the best when the ratio of hydrogel to coal was 1:10, and the grafting of chitosan did not weaken the thermal stability of the hydrogel. In addition, the thermogravimetry and differential scanning calorimetry measurement of coal with the hydrogel in air proved that the CTS--P(AA--MAA) hydrogel effectively prevented the initial oxidation of coal. Thus, CTS--P(AA--MAA) is recommended as an inhibitor in preventing coal oxidation.