Kinetic Study on Surface Modification of Ammonium Polyphosphate with Melamine

Ammonium polyphosphate (APP) and melamine (MEL) are two typical components of halogen-free intumescent flame retardants. Surface modification of APP with MEL is one solution to overcome the weak water resistance and low compatibility with polymeric materials of APP, in addition to adjusting the ratio between phosphorus and nitrogen elements. This work is focused on the kinetics of the reaction between APP and MEL. The amount of ammonia released during reaction, the grafting ratio, and the grafting efficiency were determined by elemental analysis and FTIR spectroscopy. A kinetics model was developed to quantify the reaction process. The kinetic parameters were estimated from the experimental data. It was found that the apparent reaction orders with respect to APP and MEL are 1 and 2, respectively. The frequency factor and activation energy of this reaction were determined to be 9.29 × 104 s–1 and 75.9 kJ/mol. Simulation results obtained by this model fit the experimental data well.