Bio‐Based Intumescent Flame‐Retardant Coatings for Enhanced Polypropylene Flame Retardancy

ABSTRACT Polypropylene (PP), as a widely used plastic, has its safety limited by its flammability. In response to the demand for sustainable development, this study has developed a bio‐based intumescent flame retardant (IFR) system composed of phytic acid (PA), sodium phytate (PA‐Na), and calcium gluconate (CG), which has been applied to the surface of PP by coating technology. The experiments demonstrated that, with a flame retardant addition of 40 wt.% and a coating thickness of 250 μm, the PP/(P 3 N 1 ) 6 C 1 sample achieved an increased limiting oxygen index (LOI) of 26.2%, and the vertical burning test (UL‐94) reached a V‐0 rating. Compared with pure PP, peak heat release rate (PHRR), total heat release (THR), and peak smoke production rate (PSPR) decreased by 69.3%, 25.4%, and 58%, respectively. This flame‐retardant system forms a dense char when heated, effectively isolating oxygen and slowing down heat transfer, which significantly improves the flame retardancy of PP. This study provides an effective approach to enhancing the flame retardancy of polypropylene by utilizing a bio‐based intumescent flame‐retardant coating.