Nano-violet phosphorus/nano-crystalline cellulose composite films for fire-retardant coatings†

As fire safety issues receive increasing attention, the development of efficient flame-retardant materials has become particularly important. This study explores the preparation methods of nano-violet phosphorus (NVP) and nanocellulose (NCC) composite films and their superior performance in flame retardancy applications. NVP was successfully prepared using a liquid-phase exfoliation method and was then non-covalently self-assembled with NCC to form a novel composite film with good uniformity. The microstructure, mechanical properties, and flame-retardant performance of the composite film were comprehensively characterized. The results indicated that the NVP/NCC composite film with only 1 wt% NVP exhibited significantly enhanced self-extinguishing capability (<2 s) and a peak heat release rate (23.31 kW m⁻²) and total heat release (1.78 MJ m⁻²), indicating its effectiveness in delaying the combustion process under flame exposure. The introduction of NVP made the decomposition rate of the composite film slower and the decomposition behavior more stable in an aerobic environment. In addition, the presence of NVP delayed the dehydration process of NCC, and promoted the carbonization reaction, thereby reducing the release of H₂O, thus forming a protective carbon layer and removing active free radicals, significantly improving the thermal stability and safety of the composite. This work provides important theoretical foundations and practical guidance for the development of new flame-retardant materials.