Synthesis of ammonium polyphosphate with crystalline form V (APP-V) from melamine polyphosphate (MPP)

Ammonium polyphosphate (APP) is a well known component of halogen-free flame retardants. Ammonium polyphosphate with crystalline form V (APP-V) was prepared by diammonium phosphate and melamine polyphosphate (MPP). The prepared APP-V was characterized by FTIR and XRD, its water solubility and thermal stability were tested and compared with those of APP-I, APP-II and MPP, its flame retardancy was measured by limiting oxygen index (LOI) and compared with APP-II. Finally, the synthesis mechanism of APP-V from MPP was discussed.