Preparation and Combustion Behavior of Polyamide 6/Polypropylene/Clay Nanocomposites

Polyamide 6(PA 6)/Polypropylene (PP) blends as well as PA 6/PP/clay composites were prepared by melt compounding. The distribution of clay was characterized by transmission electron microscopy. The combustion surface morphology as well as product composition after burning were studied by scanning electron microscopy along with electro-probe microanalysis. Moreover, the flame retardance and thermal stability were evaluated by a cone calorimeter together with thermogravimetric analysis. The results showed that the clay was selectively located in the PA6 phase. It is proposed that, in the presence of clay, the combustion surface changed from a branch-shaped structure to a compact carbonaceous–silicate structure. When the clay content was 3 phr, the layered silicates became enriched on part of the surface and formed an island-like structure; the islands displayed a loose cinders structure with much higher silicon content, in contrast to a branch-shaped surface with low silicon content of the surrounding polymer substrate. As the clay content continued to increase, the char covered most of the combustion surface and more clay accumulated on the burning surface. In addition, the clay particles promoted the formation of the carbonaceous–silicate structure. The peak of the heat release rate of the PA6/PP blend decreased with increasing addition of clay and the thermal stability of the PA6/PP blend also improved.