Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE An intercalated hybrid flame retardant (ODOPB-@MMT) is developed by incorporating a phosphorus-containing compound into organically modified montmorillonite. When added to aramid fiber/epoxy composites, this P–Si synergistic system achieves a UL-94 V-0 rating and 33.5% LOI at only 4 wt% loading while retaining 98.3% of the original tensile strength. The nanoscale dispersion enables simultaneous condensed-phase char reinforcement and gas-phase radical quenching.

ABSTRACT
The flammability of the epoxy matrix limits the widespread application of aramid fiber-reinforced epoxy resin (AF/EP) composites, while adding traditional flame retardants compromises their mechanical properties. To address this challenge, a novel silicon-phosphorus hybrid nano-flame retardant (ODOPB-@MMT) was successfully constructed by intercalating 10-(2,5-Dihydroxyphenyl)-10-hydrogen-9-oxa-10-phosphaphenanthrene-10-oxide (ODOPB) into organically modified montmorillonite (@MMT). This design leverages the synergistic effect between the phosphorus and silicon components to enhance flame retardancy while preserving the material's mechanical integrity. The results indicated that the obtained AF/EP composites achieved a UL-94 V-0 rating and a high Limiting Oxygen Index (LOI) of 33.5% with only a 4 wt% ODOPB-@MMT loading. Remarkably, the composites retained 98.3% of their original tensile strength, demonstrating minimal compromise on mechanical properties. During the combustion process, the peak heat release rate (p-HRR) and total heat release (THR) decreased by 48.4% and 27.5%, indicating a significant reduction in fire hazards. The flame-retardant mechanism analysis revealed the formation of a more stable and graphitized char layer in the condensed phase, alongside gas-phase radical quenching. This work provides an effective strategy for developing high-performance AF/EP composites with superior and balanced fire safety and mechanical properties.