Preparation of core-shell hybrid particles based on biomass resveratrol and phosphazene molecules co-assisted bimetallic ZIF achieves efficient flame-retardant modification and mechanical property enhancement of polyurea

Abstract

The evolution of Spray Polyurea Elastomer (SPUA) technology has revolutionized protective coating materials. While market demands have accelerated polyurea (PUA) development, achieving high-performance fire-resistant formulations remains a critical challenge. In this study, a novel core-shell hybrid flame-retardant particle, FPM@ZIF-67/ZIF-8, was successfully synthesized through the precise assembly of bimetallic ZIF onto functional polyphosphazene microspheres (FPM). By strategically incorporating biomass-derived resveratrol and phosphazene molecules to introduce flame-retardant features, such as phosphorus-nitrogen heterocycles and aromatic rings, and capitalizing on the synergistic interaction between these structures and the smoke-suppressing properties of ZIFs, highly efficient flame-retardant PUA composites were successfully prepared. Specifically, the 5 wt % FPM@ZIF-67/ZIF-8 composite achieves UL-94 V-0 rating with limiting oxygen index (LOI) increasing from 20.3 % to 28.4 %. Relative to pure PUA, reductions of 41.6 %, 40.9 %, and 37.8 % were observed in pHRR, THR, and TSP, respectively. Furthermore, robust interfacial adhesion between FPM@ZIF-67/ZIF-8 particles and the PUA matrix, combined with efficient energy dissipation mechanisms, resulted in enhanced tensile strength (20.8 MPa) and elongation at break (1014.6 %). This study advances the design of bio-derived core-shell flame-retardant hybrids, facilitating the creation of high-performance PUA elastomers with balanced fire resistance and mechanical integrity. These findings hold substantial implications for broadening PUA applications in fire-sensitive domains.