Improving the flame retardancy of intumescent flame retardant/high-density polyethylene composites using surfactant-modified montmorillonite clay

The use of layered nanomaterials in combination with intumescent flame retardant (IFR) provides an excellent means of preparing high-performance flame retardant composites. In this study, montmorillonite (MMT) was modified with two different surfactants, namely dodecyl trimethyl ammonium bromide (DTAB) and tetraphenyl phosphonium bromide (TPB), and then combined with IFR to prepare high-density polyethylene (HDPE) composites. The effects of modified MMT (P-MMT and A-MMT) on the thermal and flame retardant properties and char formation of HD/IFR/P-MMT and HD/IFR/A-MMT composites were studied. The results show that the peak heat release rate (PHRR) of HD/IFR/P-MMT and HD/IFR/A-MMT composites is reduced by 20.4% and 14.1% compared to HD/IFR composite, respectively, suggesting that P-MMT is more effective than A-MMT in improving PHRR. The use of P-MMT and A-MMT contributes to the formation of compact char residues with a graphitic structure that can act as a barrier to heat, oxygen and other combustible volatiles and thus enhances the flame retardant properties. However, A-MMT produces no significant increase in tensile strength at a low loading, while P-MMT produces a slight increase in tensile strength compared to the composite containing only IFR.