Influencing Mechanism and Interaction of Muscovite on Thermal Decomposition of Ammonium Polyphosphate

The interaction mechanism and phase evolution of ammonium polyphosphate (APP) mixed with muscovite (APP/muscovite) were studied by TG, XRD and SEM, respectively, during heating. When the temperature is not higher than 300 degrees C, muscovite has no effect on the thermal decomposition of APP, and the initial decomposition temperature of APP/muscovite at 283 degrees C is basically the same as the APP at 295 degrees C, and the main thermal decomposition products are polyphosphoric acid and NH4H2PO4 at 300 degrees C. The polyphosphoric acid, the decomposition products of APP, can enable K and Si out of muscovite and interact with muscovite chemically to generate Al(2)O3 center dot 2SiO(2), alpha-SiO2 and phosphates (AlPO4 and K5P3O10) compounds during 400 degrees C-800 degrees C, which own obvious adhesive phenomenon and porous structure with the apparent porosity of 58.4%. Further reactions between phosphates other than reactions among Al2O3 center dot 2SiO(2) and alpha-SiO2 can generate KAlP2O7 at 1 000 degrees C and the density of residual product is improved by low melting point phosphate filling pore to form relatively dense structure and decrease the apparent porosity to 44.4%. The flame resistant and self-supported ceramic materials are expected to enhance the fire-retarding synergistic effect between APP and muscovite.