Clay-Catalyzed Cracking Leads to Suppressed Flammability in Clay-Polyolefin Nanocomposites

Organoclaypolyolefin nanocomposites have been shown to exhibit slightly increased thermal stability and decreased flammability, compared to unfilled polyolefins. In contrast, we find that when the clay has not been organically modified, the resulting polyolefin nanocomposites are less thermally stable and, unexpectedly, also much less flammable. In this contribution, we investigate the mechanistic origins of these effects. Claypolyolefin nanocomposites were prepared by in situ polymerization of ethylene or propylene, using a catalyst adsorbed onto the clay. Decreased thermal stability is attributed to clay-catalyzed polymer decomposition, while decreased flammability arises in part from clay-catalyzed formation of a polyaromatic char from olefins trapped in the material by the dispersed nanofiller.