The phase and microstructure evolution of ammonium polyphosphate/ aluminium hydroxide/ mica compounds (AAM) during thermal reaction are investigated. At 300 oC, AAM residues exhibit porous structure due to gas evolution from the thermal decomposition of ammonium polyphosphate (APP) and aluminium hydroxide, but mica does not react with them, and the flexural strength of specimens can reach 11.56MPa. The thermal decomposition products of APP react with AlOOH to NH4AlP2O7, which can improve the flexural strength during 300 ~ 400 oC. The reactivity of mica is increased by eliminating hydroxyl at temperature up to 600 oC, and the flexural strength of AAM residues is improved furtherly by the chemically interactions between active mica and phosphates during 600 ~ 1000 oC. And specifically at 1000 oC, the AAM residues exhibit relatively high flexural strength, which can reach 26.85 MPa and reactions between mica and KAlP2O7 could generate KAlSi3O8 and 3Al2O3·2SiO2. AAM with high flexural strength from low to high temperatures is expected to be a kind of excellent inorganic additive of ceramifiable polymer with wide temperature range for using.

Keywords: Ammonium polyphosphate, Mica, Aluminium hydroxide, Ceramifying process, Phase compositions, Microstructures, Mechanical properties.