Molecular Formula (NH4PO3)n EINECS 269-789-9 Ammonium Polyphosphate (APP) is primarily utilized as a highly efficient core component of intumescent flame retardants (IFR). This represents its most critical and widely adopted application across industries. Flame Retardant Mechanism When exposed to high temperatures, APP undergoes thermal decomposition to generate phosphoric acid and polyphosphoric acid. These decomposition products initiate two key protective reactions: They promote the dehydration and carbonization of polymer materials, forming a dense, intumescent char layer on the material surface. This char barrier effectively isolates oxygen and heat transfer, preventing further combustion of the underlying substrate. Simultaneously, non-flammable gases are released during decomposition, which dilute the concentration of combustible gases in the surrounding environment. Through the synergistic effect of physical isolation and gas dilution, APP achieves superior flame retardancy, inhibiting flame spread and reducing smoke generation.