Application of self-templated PHMA sub-microtubes in enhancing flame-retardance and anti-dripping of PET

Tubular one-dimensional poly (cyclotriphosphazene-melamine) (PHMA) sub-microtubes were conveniently synthesized from co-polymerization of hexachloro -cyclotriphosphazene and melamine. The SEM and TEM results showed PHMA sub-microtubes were opened at one end with diameters of 100-300 nm and lengths of 1-10 μm. The inner diameters of closed and open end were 10-30 nm and 50-100 nm, respectively. The PHMA sub-microtubes were melt blended with PET (PET/PHMA) to be used as an effective flame retardant. The flame-retardant and anti-dripping properties of PET/PHMA composites were evaluated by TGA, LOI, vertical burning, MCC and rheological test. The results confirmed the efficiency of PHMA in enhancing the self-extinguishing ability and inhibiting melt-dripping of PET. The morphological characteristics and graphitic structure of the charred residues were evaluated by SEM, Raman spectroscopy. Results demonstrated the formation of a compact protective carbon layer and a carbonaceous micro-structures, which acted as insulator against oxygen and heat.