The Influence of Microwave Process and Component Ratio on Flame Retardancy of EP/IFR/MDNs/FGNs Composites

Epoxy resin (EP) is highly flammable and produces a significant amount of smoke during combustion. However, the intumescent char layer formed in EP/intumescent flame retardant (IFR) systems often lacks sufficient structural stability. In this study, molybdenum disulfide nanosheets (MDNs) and flake graphite nanosheets (FGNs) were separately prepared via microwave exfoliation and co-incorporated into the EP/IFR system at MDN: FGN mass ratios of 1:1 and 1:3. The results demonstrated that EP/IFR/(MDNs: FGNs = 1:3) exhibited reductions of 13.82%, 16.34%, 26.47%, and 36.81% in peak heat release rate (pHRR), total heat release (THR), average mass loss rate (AMLR), and total smoke production (TSP), respectively, compared with EP/IFR, indicating superior heat release suppression and smoke suppression performance. EP/IFR/(MDNs: FGNs = 1:1) showed a more pronounced inhibitory effect on peak CO and CO2 production rates, with decreases of 81.05% and 92.98%, respectively. Residue char analysis revealed that the synergistic incorporation of MDNs and FGNs enhanced the continuity, integrity, and structural stability of the intumescent char layer. Overall, adjusting the mass ratio of MDNs to FGNs optimized the condensed-phase barrier effect of the EP/IFR system, with EP/IFR/(MDNs: FGNs = 1:3) exhibiting the best overall flame-retardant and smoke-suppression performance.