Solvent-Free Synthesis of Organic–Inorganic Polyphosphoramide-Halloysite Nanohybrids for Thermally Stable and Fire-Resistant Polylactide

Biodegradable and renewable polylactide (PLA) exhibits excellent mechanical properties but is prone to high flammability, limiting its application to textiles, electronics, and packaging. In PLA, polyphosphoramides have shown their exceptional fire-retardant properties, but their existing synthesis methods often involve toxic solvents. Despite high efficiency, recently, polyphosphoramides prepared via green synthesis led to a reduced thermal stability of PLA. Herein, we report a series of organic–inorganic hybridized polyphosphoramides-halloysite nanotube nanohybrids (DM-OHn) via a one-pot solvent-free copolymerization. The results show that addition of only 1.5 wt % DM-OH16 leads to a 5 °C increase in the initial decomposition temperature of PLA and enables the latter to achieve a desired UL-94 V-0 rating and a high limiting oxygen index (ca. 32.6%), in addition to a well-preserved tensile strength. This work provides an eco-benign green strategy for the design of organic–inorganic polyphosphoramides nanohybrids for creating fire-retarding PLA with improved thermal stability and preserved mechanical strength, which are expected to be used as sustainable fireproof bioplastics for industrial applications.