Aiming to highly efficiently improve the fire safety and mechanical property of intumescent epoxy resin (EP), the interfacial aggregate of mesoporous MCM-41 nanospheres toward ammonia polyphosphate (APP) microparticles was effectively executed. Various characterizations identified the quasi-sphere-on-sphere microstructure of APP@MCM-41 with sustained thermal stability. The addition of APP@MCM-41 into EP matrix gave rise to a featured dispersion with MCM-41 preferentially located at EP/APP interface. The fire evaluation revealed that compared with pristine APP (UL-94 V-1), 9wt% APP@MCM-41 imparted EP matrix with UL-94 V-0 rating. The interfacial aggregate at the interface of EP/APP (7wt%) drove the reduction of peak heat release rate (pHRR) and total smoke production (TSP) by 30.6% and 22.2% respectively. The mechanism investigation via contrastive experiments verified that the interfacial location of MCM-41 remarkably optimized the intumescent cellular structure through the promoted catalytic charring reaction. The proposed adsorptive accumulation of EP volatiles towards EP/APP interface by mesoporous MCM-41 favored a stronger charring reaction. In addition, EP/APP@MCM-41 presented an improved mechanical performance relative to its counterparts due to an enhanced matrix-filler adhesion. In perspective, the proof of concept via interfacial assembly-induced catalytic charring associated with micro/nano hierarchy of conventional fire retardants draw a roadmap towards fire-safe polymers.
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