Flame‐Retardant Polylactic Acid Blends Incorporating Phosphorylated Chitosan and Halloysite Nanotubes

ABSTRACT Polylactic acid (PLA) is a biodegradable polymer with promising applications but suffers from high flammability and severe melt dripping. A condensed‐phase flame‐retardant system was developed by melt blending phosphorylated chitosan (PCS) and halloysite nanotubes (HNTs) into PLA. With a total loading of 9 wt% (8 wt% PCS and 1 wt% HNTs), the PLA/PCS/HNTs blend achieved a limiting oxygen index (LOI) of 29.4% and a UL‐94 V‐0 rating. Cone calorimetry results showed that the peak heat release rate (pHRR) decreased by 34.9% compared with neat PLA. The enhanced fire performance is mainly attributed to phosphorus‐induced char formation from PCS and the reinforcement of the char layer by HNTs, which promotes the formation of a compact protective barrier during combustion. These findings demonstrate that the introduction of HNTs into PLA/PCS systems provides an effective strategy for improving the fire safety of PLA composites.