SEM

XRD and TGA were used to study the characteristics of fire residues of high-impact polystyrene/arganic montmorillonite (HIPS/OMMT) nanocomposites formed during cone calorimeter tests

including residue cross-section morphology

montmorillonite platelet distribution

thermal stability and pyrolysis characteristics of the residues.The results show that the residue formed after the peak heat release rate (HRR) is composed of a thin and dense skin layer at the surface of the residue and a cellular layer beneath the skin layer.It is the skin-cellular layer structure that makes the residue layer perform a good insulation effect.XRD data and SEM observations show that the intercalated structure in the original nanocomposite is not found in the skin and cellular layers

while randomly distributed montmorillonite platelets aggregate and form a network-like structure.TGA analysis shows that both the skin layer and the cellular layer formed in the half burnt samples are mainly composed of montmorillonite with a certain amount of carbonaceous char

which not only form a protective layer

but also reduce the volatile due to the formation of carbonaceous components.Although the cellular layer is not as good as that of the skin layer in terms of permeability

the cellular layer considerably augments the thickness of the residue.It is the good combination of the skin and cellular layers that reduces the flammability of the nanocomposites.