Thermal degradation behavior and gas phase flame-retardant mechanism of diamine-based polybenzoxazine/polyhexahydrotriazine interpenetrating polymer network

It is an important research direction to improve the flame retardant properties of polymers. Benzoxazine resins have attracted a great deal of interest due to their good thermal property, but the brittleness hindered their further application. A high-toughness diamine-based polybenzoxazine/polyhexahydrotriazine interpenetrating polymer network (poly(PH-ddm)/PHT IPN) have been prepared successfully in our group. In this paper, the flame-retardant mechanism of the poly(PH-ddm)/PHT IPN was discussed. Its flammability property and the thermal decomposition mechanism were measured and analyzed with Cone Calorimeter, Thermogravimetric Analysis-Fourier Transform Infrared Spectroscopy (TGA-FTIR), and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS). The results illustrated that little heat was released during the ignition process of the cured resin. The main gas including NH3 and CO2 were generated during the thermal decomposition. With the release of these self-extinguishing gas that insulate the materials from oxygen and take away the burning heat, the poly (PH-ddm)/PHT IPN with the hexahydrotriazine structure exhibits good gas phase flame retardance.