Fabrication of halogen-free ammonium phosphate with two components via a simple method and its flame retardancy in polypropylene composites

摘要

In this paper, a halogen-free flame retardant with two different functional components was prepared via a simple method. The novelty of this work is the combination of acid source and char-forming agent in one compound simultaneously. And the advantage of this method lies in effectively avoiding the mixture of several components for composites during thermal processing and improving the flame retardancy of polymers. Besides, the chemical structure of modified ammonium phosphate (MAPP) was confirmed by Fourier transform infrared spectra (FTIR) and X-ray diffraction spectra (XRD), respectively. The results indicate that thermal decomposition process of APP after modification is obviously changed. When polypropylene (PP) is composited with 30 phr MAPP, the limiting oxygen index value can reach 28.5 % and pass vertical burning tests (UL-94) V-1 rating. Simultaneously, thermal gravimetric analysis demonstrates that the introduction of diethanolamine can improve the char-forming rate and char residue of PP/APP composites. Except that, the thermal pyrolysis of MAPP detected by FTIR spectra deduces that the char-forming process happens at 350-400 A degrees C. The analysis on char residue after combustion indicates that the cross-linking bonds of P-O-C groups appear. At last, a potential condensed mechanism was primarily proposed.