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A novel monocomponent intumescent flame retardant named pentaerythritol phosphate melamine salt (PPMS)-functionalized multiwalled carbon nanotubes (PPMS-CNT) was synthesized via grafting PPMS on the surface of multiwalled carbon nanotubes, and thoroughly characterized by Fourier transformed infrared (FTIR) spectrometry, 1 H nuclear magnetic resonance ( 1 H NMR) spectrometry, scanning electron microscope (SEM)-energy-dispersive spectroscopy (EDS), and thermogravimetric (TG) analyses. Then, PPMS-CNT was incorporated into epoxy resins (EPs) to investigate flame-retardant and smoke suppression properties. The results show that the addition of PPMS-CNT increases the limited oxygen index (LOI) and UL94 rating of EP composites, and the LOI value of EP-3 containing 15 wt% PPMS-CNT is increased to 24.5%. Cone calorimeter test indicates that the heat release and smoke production of EP composites are gradually decreased with increasing PPMS-CNT content concomitant with the increase in the intumescent factor and residual weight. Thermogravimetric analysis shows that the thermal stability and char-forming ability of the EP composites are increasingly improved with increasing PPMS-CNT content. Char residue analysis reveals that the same addition of PPMS-CNT tends to form a more continuous and compact char than that of PPMS because of more phosphorus-rich cross-linking char and aromatic char remained in the condensed phase, thus exhibiting higher flame-retardant and smoke suppression efficiencies in EP matrix. Overall, PPMS-CNT can serve as a promising monocomponent intumescent flame retardant for reducing the flammability and smoke emission characteristics of EP materials. KEYWORDS flame retardancy, intumescent flame retardant, multiwalled carbon nanotubes, smoke suppression, thermal stability

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