Combination of graphene and montmorillonite reduces the flammability of poly(vinyl alcohol) nanocomposites

A combination effect is observed between graphene and montmorillonite (Mt) in poly(vinyl alcohol) (PVA) composites. The results from X-ray diffraction (XRD) and transmission electron microscopy (TEM) show that both graphene sheets and Mt layers achieve fine dispersion in PVA matrix and Mt/graphene/PVA nanocomposites are formed. Thermal stability and flammability properties were investigated by thermogravimetric analysis (TGA) and cone calorimeter tests. The results show that the combination effect of graphene and Mt improves thermal stability and reduces significantly the flammability (including heat release rate (HRR), total heat release (THR), time to ignition (TTI), etc.). The peak heat release rate (PHRR) of Mt/graphene/PVA is reduced by about 49% compared with pure PVA. The morphology of residues generated after cone calorimeter tests was investigated by scanning electronic microscopy (SEM), and the results indicate that a compact and dense char is formed for Mt/graphene/PVA nanocomposites after combustion.