A thermostable phosphorus/nitrogen-based flame retardant with enhanced compatibility with PET

Poly(ethylene terephthalate) (PET) presents a persistent challenge in achieving satisfactory fire safety while maintaining its melt spinnability primarily due to its poor compatibility with flame retardants (FRs). In this study, the issue was effectively addressed through the application of suitable phosphorus/nitrogen (P/N)-based FRs (PBPO), which can form strong hydrogen bonding with PET and have a close melting temperature (Tm) to PET. As a result, the prepared PET/PBPO composites showed high fire safety and good melt spinnability simultaneously. Specifically, PET/PBPO6 (containing 6 wt% of PBPO in PET) exhibited a peak heat release rate (PHRR) over 30 % lower than that of pure PET, and was found to be non-ignitable with only one molten droplet generated during the vertical burning test, achieving the UL 94 V-0 level. Significantly, PET/PBPO6 filaments, which were prepared by melt spinning the PET/PBPO6, showed pleasing tensile properties and were self-extinguished within 3 s.