Synthesis and Characterization of Polyacrylonitrile Copolymers With Enhanced Flame‐Retardant and Smoke‐Suppressing Properties

ABSTRACT An intrinsic flame‐retardant P(AN‐ co ‐IPADE) copolymer was synthesized via aqueous deposited polymerization, enhancing the thermal stability and flame retardancy of polyacrylonitrile (PAN). Limiting oxygen index (LOI), cone calorimetry, and thermogravimetric analysis (TGA) were used to reveal significant improvements in flame retardancy and thermal stability due to the integration of isopropenyl‐phosphonic acid dimethyl ester (IPADE). Notably, the copolymer exhibited an LOI value of 31.0% with an IPADE content of just 20.4 wt%, and a remarkable 80% reduction in both the peak heat release rate and total heat release, underscoring its exceptional flame‐retardant properties. The emission of hazardous smoke components, including hydrogen cyanide (HCN), nitrogen oxides (NO x ), and carbon monoxide (CO), was effectively mitigated. The flame‐retardant mechanism was explored, and the bond dissociation enthalpy (BDE) of the primary groups within the polymer chains was calculated to understand the pyrolysis process. Complementary analyses using X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy, and pyrolysis‐gas chromatography–mass spectrometry (Py/GC–MS) suggest that IPADE contributes to both the gaseous and condensed phases, forming a comprehensive flame‐retardant mechanism.