P/N Zinc salt containing biological groups for synchronously enhanced the fire safety, anti-dripping and mechanical properties of polylactic acid

As a promising biodegradable alternative to petroleum-based plastics, Polylactic acid (PLA) faces significant challenges in industrial applications due to its inherent flammability and brittleness, necessitating material modifications for expanded utilization. This study addresses the critical challenges of flammability and brittleness in PLA through the development of a novel bio-based anti-dripping flame retardant system. A phosphorus‑nitrogen containing flame retardant (AAPZ), was successfully synthesized and incorporated with ammonium polyphosphate (APP) to create high-performance PLA composites. The optimized PLA/4.5APP/4.5AAPZ composite demonstrated exceptional flame retardancy, passing a UL-94 V-0 rating with complete suppression of melt dripping. Cone calorimetry analysis revealed significant improvements in fire safety, with peak heat release rate (PHRR) and total smoke release (TSR) reduced by 60.2 % and 28.3 %, respectively, compared to neat PLA. Remarkably, the composite maintained excellent mechanical properties, exhibiting a 185 % increase in elongation at break while preserving tensile strength. The synergistic flame-retardant mechanism was systematically investigated, demonstrating effective gas-phase and condensed-phase actions. This bio-based flame-retardant system not only overcomes the inherent limitations of PLA but also provides a sustainable solution for expanding its applications in demanding sectors.