The influence of carbon nanotubes, organically modified montmorillonites and layered double hydroxides on the thermal degradation and fire retardancy of polyethylene, ethylene-vinyl acetate copolymer and polystyrene

Nanocomposites of polyethylene, ethylene-vinyl acetate copolymer and polystyrene with single- and multi-wall carbon nanotubes, organically modified montmorillonites and layered double hydroxides were prepared by melt blending. Their morphologies were assessed by X-ray diffraction and transmission electron microscopy, while the flammability properties were evaluated by thermogravimetric analysis and cone calorimetry. The relative amounts and the identity of the degradation products are changed when both well-dispersed cationic and anionic clays are used, but there is no difference in the degradation products when carbon nanotubes were utilized. When the nano-dimensional material is not well-dispersed, the degradation products are not changed. Unlike their smectite counterparts, polymer/layered double hydroxide nanocomposites give reasonably good reductions in peak heat release even when good nano-dispersion has not been obtained. These data suggest that the enhancement in the fire behavior must be, at least in part, due to different mechanisms for montmorillonite, layered double hydroxides and carbon nanotube-based nanocomposites.