Synergistic effect of organophilic Fe-montmorillonite on flammability in polypropylene/intumescent flame retardant system

Polypropylene/intumescent flame retardant/organophilic Fe-montmorillonite (PP/IFR/Fe-OMT) nanocomposites were prepared by melting intercalation. In order to investigate the effect of structural Fe³⁺ in the PP/IFR system, the corresponding PP/IFR and PP/IFR/Na-OMT composites were prepared under the same conditions. The thermo-gravimetric analysis data show that the PP/IFR/Fe-OMT nanocomposites have higher thermal stability than the PP/IFR and PP/IFR/Na-OMT composites. The flame retardant results indicate that the limiting oxygen index values of the nanocomposites with Fe-OMT are basically higher than those of the pure PP and the composites containing IFR or Na-OMT/IFR. And the addition of a suitable amount of Fe-OMT in PP/IFR composites can apparently favor UL94 test, and no dripping phenomenon was found. The cone calorimeter test indicates that the heat release rate (HRR) is significantly reduced by the formation of the nanocomposites, and the HRR of the PP/IFR/Fe-OMT nanocomposites are decreased in comparison with those of the PP/IFR/Na-OMT nanocomposites. It is noteworthy that Fe-OMT is helpful to smoke suppression by smoke density test.