Polyaniline‐Microencapsulation of Ammonium Polyphosphate and Its Flame Retardancy in Coatings

ABSTRACT To improve the water resistance, flame retardancy, and compatibility with coating substrates of high‐polymerization ammonium polyphosphate (APP, n ≥ 1000), APP was encapsulated with in situ polymerization using polyaniline (PANI) as the shell material to produce the microencapsulation ammonium polyphosphate (MAPP). The core‐shell structure of MAPP was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The effects of preparation parameters on MAPP performance were investigated by measuring the solubility, coating rate, particle size, thermogravimetric properties, and flame retardancy. The MAPP prepared under the conditions of m PANI / m APP of 0.75, phosphoric acid doping, and reaction time of 4 h has the optimal comprehensive properties. The flame retardancy was characterized by cone calorimeter testing (CONE), fire resistance experiments, and Raman spectroscopy. MAPP is found to be more compatible with coating base material than APP is. Reduced total heat release rate (THR) and peak heat release rate (PHRR) are found in the flame‐retardant coating with MAPP, and the amount of combustion char residue increases. The carbon layer formed in combustion is more continuous and dense as compared to coatings with APP. Furthermore, thermal decomposition kinetics show that the PANI microencapsulation of APP increases the decomposition activation energy of the coatings.