Polymer nanocomposite exposed to heat, polymeric material burned at slower rate (reduced mass loss rate)
As polymer burned away, clay rich carbon barrier forms.
Final char formed at end of burning very rich in clay content. Clay slows down mass loss rate and reduces heat release rate, but it does not stop burning.
Nanotubes and nanofibers have similar mechanism (reduced mass loss rate) but instead create a network “web” of fibers which keep polymer mass from pyrolyzing.