Directional BN alignment via Fe3O4 with Tri-source engineered ATP for enhanced fireproofing performance of waterborne epoxy

The inherent flammability of epoxy resins (EP) limits their application in safety-critical areas. This study proposes a structurally ordered and synergistically flame-retardant strategy to address this issue. Initially, polydopamine (PDA) serves as a functional bridging layer to facilitate uniform deposition of Fe 3 O 4 nanoparticles onto boron nitride (BN) nanosheets, constructing a magnetically responsive interface. Subsequently, adenosine triphosphate (ATP) is introduced through copolymerization to form a novel composite flame retardant BN-Fe 3 O 4 @PATP (PATP is a copolymer of polydopamine and adenosine triphosphate). Under magnetic field induction, the BN loaded with Fe 3 O 4 nanoparticles achieves directional alignment within the epoxy resin matrix, forming an efficient physical thermal barrier. Simultaneously, the transition metal oxide Fe 3 O 4 can enhance the formation of residual charcoal. Furthermore, the acid source (phosphate groups), carbon source (polyhydroxy compounds), and gas source (amino groups) within ATP structure can generate an expanded char layer at high temperatures, thus improving its thermal shielding performance. Experimental results demonstrated significantly enhanced flame retardancy of the BN-Fe 3 O 4 @PATP/EP composite system compared to pure EP: peak heat release rate (PHRR), total heat release rate (THR), peak smoke release rate (PSPR), and total smoke release rate (TSR) were reduced by 39.8 %, 24.8 %, 36.8 %, and 44.3 %, respectively. Compared with pure epoxy and other epoxy composites, BN-Fe 3 O 4 @PATP/EP system also exhibits the lowest peak carbon monoxide (PCOPR) and carbon dioxide (PCO 2 PR) evolution rates, while the char residue rises significantly from 14.6 % (pure EP) to 28.8 %. By achieving magnetic field-induced ordered arrangement of BN combined with catalytic char-forming effect and intumescent flame-retardant mechanism, this work constructs a multifunctional flame-retardant system endowed with thermal insulation, smoke suppression, and toxicity reduction capabilities, providing a new strategy for the flame retardancy of EP.