Piperazine polypyrophosphat-halloysite nanotubes-melamine cyanurate synergistic flame retardant epoxy resin

Abstract

By improving the existing preparation methods, a piperazine polypyrophosphat (PAPP) with high thermal stability was synthesized. It was compounded with halloysite nanotube (HNTs) and melamine cyanurate (MCA) to form P-N-Si intumescent flame retardant, and was used in synergistic flame retardant epoxy resin (EP). The effect of intumescent flame retardant on the flame retardancy of EP was investigated by means of limiting oxygen index, vertical combustion, cone calorimeter and SEM etc. The results show that the introduction of the compound flame retardant forms a dense and continuous intumescent carbon layer, which improves the flame retardant efficiency of the epoxy resin in the condensed phase and the gas phase. It reduces the heat release and heat release rate of epoxy resin and the toxic gases release effectively. When the PAPP/HNTs/MCA ratio is 7∶1∶2, the limiting oxygen index of flame retardant resin reaches 34.3%, the UL-94 vertical combustion test reaches V-0 level. Compared with pure EP, the amount of residual carbon is increased significantly, the peak heat release rate (HRR) is decreased by 60.56%, and the total heat release (THR) and toxic gas emissions are reduced significantly for modified EP. In addition, the thermogravimetric analysis results suggest that the initial decomposition temperature of flame retardant modified EP is decreased by 4.4% (ΔT), and the modified EP still has high thermal stability.

Keywords

• epoxy resin
• intumescent flame retardant
• flame retardancy
• thermal stability
• piperazine polypyrophosphat