Flammability of Polystyrene Layered Silicate (Clay) Nanocomposites: Carbonaceous Char Formation.
Flammability of Polystyrene Layered Silicate (Clay)
Nanocomposites: Carbonaceous Char Formation.
Morgan, A. B.; Harris, R. H., Jr.; Kashiwagi, T.;
Chyall, L. J.; Gilman, J. W.
Fire and Materials, Vol. 26, No. 6, 247-253,
polystyrene; flammability; nanocomposites; char
formation; mechanical properties; flame retardants; clay
Polymer layered-silicate (clay) nanocomposites have not
only the unique advantage of reduced flammability, but
also improved mechanical properties. This is a key
advantage over many flame retardants, which reduce
flammability but also reduce the mechanical properties
of the polymer. In our efforts to further understand the
mechanism of flame retardancy with polymer-clay
nanocomposites, we investigated the effect of the clay,
the loading level and polymer melt viscosity on the
flammability of polystyrene-clay nanocomposites. The
nanoscale dispersion of the clay in the polymer was
analysed by wide-angle X-ray diffraction (XRD) and
transmission electron microscopy (TEM). Cone calorimetry
and gasification studies were used to evaluate the
flammability of these nanocomposites. There were major
reductions in peak heat release rates (HRRs), and
increased carbonaceous char formation, for these
nanocomposites. It was determined that while the
viscosity of the PS nanocomposite played a role in
lowering the peak HRR, the clay loading level had the
largest effect on peak HRR. Finally, it was found that
clay catalysed carbonaceous char formation, and the
reinforcement of the char by the clay was responsible
for the lowered flammability of these nanocomposites.