Synthesis of amino trimethylene phosphonic acid melamine salt and its application in flame‐retarded polypropylene

Amino trimethylene phosphonic acid melamine salt (MATMP) was synthesized and used as acid source and blowing agent in intumescent flame‐retarded polypropylene (PP); its compositions were characterized by Fourier transform infrared spectroscopy and X‐ray powder diffraction. An intumescent flame retardant (IFR) system composed of MATMP, pentaerythritol (PER), and PP was tested by limiting oxygen index (LOI), UL‐94, cone calorimeter tests, and thermogravimetric analysis and compared with an ammonium polyphosphate (APP)/PER system. The results showed that MATMP had better water resistance than APP, the LOI value of PP/MATMP/PER composite can reach 30.3%, and a UL‐94 V‐0 rating can be reached at 25 wt % IFR loading. The amount of residual char of IFR MATMP/PER was 20.3 and 9.5 wt % at 400 and 600 °C, respectively. A thermooxidative degradation route and a possible flame‐retardant mechanism of IFR were proposed according to the analysis of evolved gases and residual chars. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46274.