Structural characterization of sepiolite/polyamide6,6 nanocomposites by means of static and dynamic thermal methods

Clay Polymer Nanocomposites (CPN) are hybrid materials with improved technical characteristics with respect to the counterparts. Polyamide6,6 (PA66) is one of the most widely used as matrix. The a structure (triclinic) undergoes into the gamma structure (pseudohexagonal) in a solid-to-solid transition when exposed to high temperatures. In recent years, sepiolite (Sep) has been used as reinforcing agent in polymer matrix as it enhances thermal properties of the nanocomposites without modification in the hydrogen bonds between PA66 chains. In this work we provide information about the structural changes occurring in neat PA66 and Sep/PA66 nano composites after the degradation process through a thermo-dynamic study combined with X-ray diffraction methods. In injection molded Sep/PA66 nanocomposites the sepiolite fibres locate between the polymer lamellae in a sloping suitable position, without involving large distortions in the lattice of PA66. Due to organophilization, no changes are induced by the sepiolite in the nanocomposite structure. The PA66(center dot center dot center dot)Sep contact promotes the occurrence of the C-H center dot center dot center dot O hydrogen bonds in the typical reticulated structure between the sepiolite fibres and the polyamide chains, which renders thermal sability to the polymer crystals up to 150 degrees C.