Study of Polyphosphazenes‐Coated Carbon Microspheres and Their Application in <scp>PET</scp> Modification

ABSTRACT In this study, core‐shell carbon microspheres (CMSs‐PZS) were synthesized by coating polyphosphazene (PZS) on the surface of carbon microspheres (CMSs) through one‐step polymerization, and they were characterized using infrared spectroscopy and electron microscopy tests. CMSs‐PZS were added to polyethylene terephthalate (PET) to prepare flame‐retardant PET composites. The effects of CMSs‐PZS on the flame retardancy, thermal stability, and mechanical properties of the composites were investigated. The results showed that the introduction of CMSs‐PZS into PET significantly enhanced the flame‐retardant properties. When the content of CMSs‐PZS was 3 wt%, the limiting oxygen index (LOI) value of PET/CMSs‐PZS increased to 33.4%, achieving a UL‐94 V‐0 rating. Thermogravimetric (TG) analysis showed that the initial decomposition temperature of PET composites increased, while the decomposition rate decreased, and the amount of residual carbon increased with the addition of CMSs‐PZS. Cone calorimeter test data showed that the peak heat release rate (pk‐HRR) of PET/3wt%CMSs‐PZS decreased to 450.67 kW/m 2 , and the total heat release (THR) decreased to 22.14 MJ/m 2 . It is shown that during the combustion process, CMSs‐PZS decomposes to form a charcoal layer covering the surface of PET, which plays the role of heat and oxygen insulation, effectively inhibiting the combustion of PET and its heat release during the combustion process.