Melamine pyrophosphate(MPP)was combined with expanded graphite(EG),and rigid polyurethane foam/expanded graphite/melamine pyrophosphate(RPUF/EG/MPP)composites were prepared by a one-step all-water-blown method.On this basis,thermogravimetric analysis(TG),flame retardant tests,microscale combustion calorimeter(MCC)and scanning electron microscope(SEM)were applied to investigate the thermal stability,flame retardancy,combustion property and char residue micromorphology of the RPUF/EG/MPP composites.The results show that the incorporation of MPP and EG can significantly enhance thermal stability of the composites.RPUF-2 with MPP of 40.6 phr and EG of 20.3 phr has a high carbon yield of 31.7%at 800 o C.The flame retardant tests show the synergistic effect between MPP and EG,the maximal limiting oxygen index of RPUF/EG/MPP composites is 29.9%.MCC tests show that the addition of MPP and EG could effectively decrease the heat release of the composites during combustion,enhancing the fire safety of the composites.
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