Burning behavior and pyrolysis products of flame-retardant PET containing sulfur-containing aryl polyphosphonate

The flame retardant action of a sulfur-containing polyphosphonate, poly(9-oxa-10-(2,5-dihyro-xyphenyl) phosphaphenanthrene-10-oxide) phenylthiophosphonate (PDPTP), on Poly(ethylene terephthalate) (PET) was investigated using FTIR, Py-GC/MS and Cone calorimetry methods. The results show that the contents of flammable small molecular compounds generated during combustion are sharply reduced, which proves that the extensive pyrolysis of PET is retarded by the existence of PDPTP. Moreover, PDPTP does not change the mechanism of pyrolysis of PET. According to the results of fire test using Cone calorimetry, the ignition time of PET is prolonged, the heat release rate and effective heat of combustion of PET decreases drastically, and the amount of char residue increases due to the addition of PDPTP, proving the excellent flame retardancy of PDPTP. Besides, the specific extinction area also decreased after adding PDPTP, suggesting an improved smoke suppressing behavior.