Genistein‐Derived Intumescent Flame‐Retardant System: Synergistic Enhancement of Flame Retardancy, Smoke Suppression, and Mechanical Properties for Epoxy Resins

ABSTRACT The growing demand for sustainable and safe polymeric materials has necessitated the development of bio‐based flame retardants. Herein, a novel halogen‐free, bio‐based flame retardant, genistein triphosphate (GSP), was successfully synthesized and combined with ammonium polyphosphate (APP) to construct an efficient binary intumescent flame‐retardant system (APP@GSP) for EP. With 15 wt% APP@GSP loading, the EP composite exhibited limiting oxygen index (LOI) of 31.0%, reaching the classification of UL‐94V‐0. Moreover, peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) decreased by 80.2%, 53.2%, and 55.3%, respectively, along with a high char yield of 64.6 wt%. A synergistic flame‐retardant mechanism has been confirmed by the characterization of char residues and gaseous pyrolysis products: APP@GSP promotes the formation of a dense and continuous char layer in condensed phase; concurrently, the flame retardant facilitates the release of nonflammable gases and radical scavengers in gas phase. In addition, APP@GSP also improved the mechanical properties of EP composites, with enhancement in both tensile strength and toughness. Such a dual optimization is attributed to the improved interfacial compatibility. This work presents a sustainable and effective strategy for developing high‐performance EP composites with balanced fire safety and mechanical properties.