A highly thermostable flame retardant for poly(ethylene terephthalate) and its fabric with satisfactory comprehensive flame retardancy

The charring enhancement of polymers at high temperatures is essential for improving their anti-dripping, flame inhibition and smoke suppression performance. In this work, a highly thermostable and charring phosphorus-nitrogen (P/N)-based flame retardant (HMCP), which can boost the char-forming of poly(ethylene terephthalate) (PET) was synthesized. Amazingly, melt-dripping of PET was completely suppressed as 4 wt% of HMCP was added. For PET composite with 8 wt% of HMCP (PET/HMCP8), its limiting oxygen index increased to 33.6% and the flame self-extinguished within 5 s. Besides, the after-flame time and total smoke production of PET/HMCP8 were reduced by 96.1% and 39.5% respectively compared with pure PET. The enhanced fire safety of PET/HMCP composites was attributed to the barrier effect and the dilution effect produced by the synergism of P/N-based heterocycle and benzimidazole groups. Additionally, PET fabric woven with the filaments prepared by the melt spinning of PET/HBCP4 presented pleasing fire safety and mechanical properties.