The flame retardancy and thermal property of poly (ethylene terephthalate)/cyclotriphosphazene modified by montmorillonite system

The flame retardancy and thermal properties of neat poly (ethylene terephthalate) (PET) and flame-retarded PET were investigated. hexachlorocyclotriphosphazene modified by montmorillonite (HCCP-OMMT) was used as the flame retardant. The composites were prepared by melt blending neat PET with flame retardant and named as PET/HCCP-OMMT. Three levels of HCCP-OMMT (1%, 3% and 5%) were considered for the blends. Thermal property of PET/HCCP-OMMT composites was studied by thermogravimetric analysis (TGA), and only 3% additive was found to significantly enhance the thermal stability of PET both in air and nitrogen at high temperature. It was found that the composites could pass UL-94 V-0 and LOI value 31.5 just containing 3% of HCCP-OMMT. The Py-GC/MS study showed that the cyclotriphosphazene and montmorillonite still remained in the residue during the pyrolysis of HCCP-OMMT. Besides that, the introduction of HCCP-OMMT would inhibit the pyrolysis of PET during heating or burning. The morphology and the chemical structure of the charred residue were detected by SEM and FTIR respectively. Results demonstrated that a good barrier was provided by the char of composites and improved the thermal behaviors during burning. TEM results suggested that intercalating type composite by melt blending can be formed.