Phosphorus-functionalized Schiff base flame retardant for PET and its filaments: enhancing fire resistance, anti-dripping, and strength

The combination of enhanced char formation capacity and radical quenching effect in polymer materials at elevated temperatures is crucial for improving flame inhibition and anti-dripping performance. This study developed a phosphorus (P)-functionalized Schiff base flame retardant (HSCP) specifically for poly(ethylene terephthalate) (PET). Notably, incorporation of merely 4 wt% of HSCP effectively enhanced the anti-dripping performance of PET. The PET composites containing 8 wt% of HSCP (PET/HSCP8) achieved a limiting oxygen index of 30.0% with complete anti-dripping performance, attaining a V-0 rating in vertical burning. Furthermore, PET/HSCP8 exhibited a remarkable 16.4% reduction in total smoke production compared to unmodified PET. The enhanced fire safety of PET/HSCP was achieved through the dual-phase mechanism of HSCP, which combines the char-forming effect with the quenching effect. Importantly, the PET/HSCP8 composites maintain excellent interfacial compatibility, enabling the successful fabrication of filaments through melt-spinning that simultaneously exhibit enhanced fire safety and preserved mechanical properties.