Phytic Acid and Melamine Self‐Assembled Macromolecule‐Coated Montmorillonite for Flame‐Retardant Polyvinyl Alcohol Film

ABSTRACT A green and bio‐based flame retardant, MMT@PAMEL, was synthesized by coating phytic acid (PA) and melamine (MEL) self‐assembled macromolecules onto the surface of montmorillonite (MMT) nanosheets. This novel flame retardant was employed to enhance the fire resistance of polyvinyl alcohol (PVA) films. To evaluate its fire performance, several standard tests were conducted, including the limiting oxygen index (LOI), vertical burning (UL 94), and cone calorimetry. The findings revealed a substantial enhancement in flame resistance. The LOI value of the PVA/MMT@PAMEL‐15 composite film increased significantly from 19% (pure PVA) to 31%, achieving a UL 94 VTM‐0 rating. Moreover, the peak heat release rate (PHRR) and total heat release (THR) of the PVA/MMT@PAMEL‐5 composite film were reduced to 108.98 kW/m 2 and 2.71 MJ/m 2 , representing reductions of 57.11% and 33.42%, respectively, compared to the pure PVA film. The underlying flame‐retardant mechanism was explored through thermogravimetric‐infrared spectroscopy (TG‐IR), scanning electron microscopy (SEM), Raman spectroscopy, and infrared spectroscopy. The results revealed that the primary mechanism involved PA decomposition during combustion, which released phosphorus‐containing compounds that promoted the esterification of PVA, leading to the formation of char precursors. Additionally, the barrier effect of MMT contributed to the formation of a phosphorus‐carbon composite, thereby reinforcing a continuous and compact carbon layer. Simultaneously, MEL released NH 3 and other non‐combustible gases, which diluted the concentration of flammable gases and absorbed heat, forming a protective gas layer. These combined mechanisms significantly enhanced the fire resistance of the PVA composite films, providing a sustainable solution for improving fire safety in polymer materials.