Improving the flame resistance and thermal conductivity of ethylene‐vinyl acetate composites by incorporating hexachlorocyclotriphosphazene‐modified graphite and carbon nanotubes

Graphite has been regarded as a promising additive for improving the fire safety and thermal conductivity (TC) of polymers. In this article, graphite was modified by grafting with hexachlorocyclotriphosphazene to prepare a novel modified graphite oxide (M‐GO). M‐GO in association with multiwalled carbon nanotubes (MWNT) were introduced into ethylene‐vinyl acetate (EVA) by melt compounding to prepare bifunctional composites with excellent fire resistance and TC. The flammability of the EVA composites was characterized by limiting oxygen index (LOI), vertical burning (UL‐94), and cone calorimeter test. The results showed that the sample containing 18% M‐GO and 2% MWNT achieved the maximal LOI value of 31.6%, passed the UL‐94 V‐0 rating, and significantly decreased the peak heat release rate from 1383.7 kW/m² of neat EVA to 558.3 kW/m². The TC of the EVA composites was characterized by a TC analyzer, and the results showed that the presence of M‐GO and MWNT could significantly increase the TC by the formation of more efficient thermal transfer pathways. The thermal behaviors of EVA composites and the morphologies of residues were characterized and the possible mechanisms were also proposed. POLYM. COMPOS., 39:E891–E901, 2018. © 2017 Society of Plastics Engineers