Various amounts (up to 10 wt%) of palygorskite nanofibers functionalized by 3-aminopropyltriethoxysilane (APTES) coupling agent were used to reinforce polyamide 11 nanocomposites prepared by melt compounding. The covalent bonding of the silane on the palygorskite surface was confirmed by infrared spectroscopy and thermogravimetric analysis. X-ray diffraction revealed the retention of the α-form of polyamide crystals upon the addition of both natural and silane treated palygorskite nanorods. All the investigated nanocomposites showed an improvement of the thermal stability, especially when surface treated palygorskite nanofibers were considered. Tensile tests and dynamic mechanical thermal analyses on the prepared materials evidenced how the incorporation of palygorskite nanofibers significantly increased the elastic and the storage moduli of polyamide, and this enhancement was more evident when natural palygorskite nanorods were used.

Pyrolysis and fire behaviour of palygorskite (Pal) fibrous clay (5 wt%) reinforced polyamide 11 nanocomposites prepared by melt compounding were investigated in combination with melamine polyphosphate (MPP). Palygorskite was modified by 3-amino-propyl-triethoxysilane (APTES). Thermal stability and combustion behaviour of the materials were studied by thermogravimetric analysis (TGA), pyrolysis combustion flow calorimeter (PCFC) and cone calorimeter. TGA data showed that MPP reduced the thermal stability of PA11 nanocomposites, whereas the addition of both unmodified and modified palygorskite improved this property. Further, the cone calorimeter and PCFC results indicated a significant decrease in the peak of heat release rate (pHRR) and the total heat release (THR) of PA11 nanocomposites. This also means that the PA11 combustion was strongly reduced in the presence of combined Pal with MPP, being however more pronounced for the modified palygorskite. The improved fire behaviour could be attributed to a synergistic effect between Pal and MPP.