Thermal stability and flame retardant effects of halloysite nanotubes on poly(propylene)

Naturally occurred halloysite nanotubes (HNTs) with hollow nanotubular structures were used as a new type filler for poly(propylene) (PP). Nanocomposites based on PP and HNTs were prepared by melt blending. Scanning electronic microscopy (SEM) results suggested HNTs were dispersed in PP matrix evenly at nanoscale after facile modification. Thermal stability of the nanocomposites was found remarkably enhanced by the incorporation of HNTs. Cone calorimetric data also showed the decrease of flammability of the nanocomposites. Entrapment mechanism of the decomposition products in HNTs was proposed to explain the enhancement of thermal stability of the nanocomposites. The barriers for heat and mass transport, the presence of iron in HNTs, are all responsible for the improvement in thermal stability and decrease in flammability. Those results suggested potential promising flame retardant application of HNTs in PP.