Synthesis and Application of a Novel Polyamide Charring Agent for Halogen-Free Flame Retardant Polypropylene

A novel charring agent, poly(p-ethylene terephthalamide) (PETA), for halogen-free flame retardant polypropylene was synthesized by using p-phthaloyl chloride (TPC) and ethylenediamine through solution polycondensation at low temperature, and the effects of PETA on flame retardance of polypropylene (PP)/IFR systems were studied. The experimental results showed that PETA could considerably enhance the fire retardant performance as proved by evidence of the increase of limiting oxygen index (LOI) values, the results of UL-94 tests, and cone calorimeter tests (CCT). Fourier transforminfrared spectroscopy (FTIR) and scanning electron microscope (SEM) demonstrated that an appropriate amount of PETA could react with PP/IFR systemto formcross-link network; a more compact char layer could be formed which was responsible for the improved thermal and flame retardant properties of PP/IFR systems. However, the superfluous amount of PETAwould play the negative role.