Polyvinyl Alcohol Films Based on Supramolecular Flame Retardant: Towards Simultaneous Enhancement of Flame Retardancy, Mechanical Properties, and UV Resistance

Polyvinyl alcohol (PVA) is a biodegradable, water-soluble polymer with excellent film-forming properties, but its flammability severely limits its applications. A key challenge in PVA functionalization research is enhancing flame retardancy of PVA films. It must be achieved without compromising transparency and mechanical properties. This work presents a novel supramolecular flame retardant, DAD@Ni, containing nitrogen, phosphorus, sulfur, and nickel. It is synthesized via ion-metal ligand coordination and incorporated into PVA to form PVA/DAD@Ni composites. The PVA/10%-DAD@Ni composite's limiting oxygen index (LOI) increased from 19.0% as in pure PVA film to 32.3% and achieved the ideal UL-94 V-0 rating. Meanwhile, its peak heat release rate (PHRR) and total heat release (THR) were reduced by 63.3% and 46.8%. Compared to pure PVA film, PVA/DAD@Ni composites demonstrated excellent UV resistance in the UVA and UVB regions. The investigation revealed that integrating PVA and DAD@Ni, facilitated by a hydrogen-bonded cross-linked network, enhanced mechanical properties while preserving optical clarity in composites. This work presents a feasible method for fabricating multifunctional, flame-retardant, and UV-resistant materials. The PVA/DAD@Ni composites has potential applications in outdoor protective materials, electronic device packaging, safety protective equipment, and other fields.