Mussel-inspired fabrication of PDA@MOFs biomimetic microcapsules for flame-retardant epoxy composites: A comparative study on fire safety and mechanical enhancement

Epoxy resin (EP), a widely utilized thermosetting polymer, is inherently flammable and poses significant fire hazards. Drawing inspiration from the surface chemistry of mussels, this study presents the fabrication of biomimetic flame-retardant microcapsules, termed PDA@MOFs (M = Cu, Fe, Co) at room temperature and pressure for meeting the requirements of intrinsic safety. These microcapsules were synthesized through the oxidative self-polymerization of dopamine (DA) under alkaline conditions, resulting in polydopamine (PDA) on the surface of metal-organic frameworks (MOFs). We incorporated these PDA@MOFs into EP matrix to evaluate their impact on the mechanical and flame-retardant properties of EP composites. Compared to unmodified EP/MOFs, EP/PDA@MOFs exhibited enhanced interfacial compatibility and improved mechanical performance. Limiting oxygen index (LOI), vertical burning (UL-94), and cone calorimetry test (CCT) confirmed that PDA@MOFs significantly enhanced the flame retardancy and smoke suppression. Among them, EP/PDA@Co-MOF demonstrated the best performance, achieving a 32.2% reduction in peak heat release rate (pHRR) and a 14.2% decrease in total heat release (THR) compared to neat EP. Furthermore, residual char analysis revealed that the flame-retardant mechanism involved physical barrier effect, catalytic char formation, and radical trapping, establishing a foundation for designing high-performance flame-retardant EP composites.