Abstract: The temperature- sensitive hydrogels were prepared by methyl cellulose (MC), polyethylene glycol (PEG) and sodium chloride (NaCl) as raw materials, and the flame retardant ammonium polyphosphate (APP) was added to this system. The mass fraction ratio of the material system was optimized as MC∶PEG∶NaCl∶APP = 1.3∶5.0∶5.0∶1.5. LCST was measured at 58 ℃ by tube inversion method. The structure of hydrogels was characterized by Fourier infrared spectroscopy (FT- IR), and the thermal stability and flame retardancy of hydrogels were measured by thermal gravimetric analysis (TG) and cone calorimeter. Experimental results showed that there is no chemical action in the mixture system of materials. Comparing with untreated boards and water- soaked boa-rds, the initiation time and peak occurrence time of the heat release rate of the board soaked in the temperature- sensitive hydrogel were significantly delayed. Compared with untreated wood, the ignition time of wood boards immersed in temperature- sensitive hydrogel was delayed by 76 s, the peak time of the first and second heat release rate was delayed by 83 s and 269 s, respectively, indicating that the temperature- sensitive hydrogel under the preparation system had good flame retardant performance.

Key words: temperature- sensitive polymer, thermal stability, methylcellulose, volume phase transition, flame retardant property