Preparation and characterization of new melt compounded copolyamide nanocomposites

In this work new copolyamide-layered silicate nanocomposites were prepared by melt compounding using a commercial polyamide 6-based copolymer, with a partially aromatic structure, as thermoplastic matrix. This copolyamide, having a lower melting point and improved mechanical and barrier properties respect to the homopolymer, appears an interesting material for producing nanocomposite packaging films. Hybrids with different organoclay loadings were produced by a twin-screw extruder using different extrusion rates, in order to point out the effects of both processing conditions and hybrid composition on morphology (silicate dispersion and exfoliation, orientation, matrix crystallinity) of nanocomposites. All melt-intercalated samples were submitted to structural (TEM and XRD), thermal and dynamic mechanical measurements. The performed analyses have evidenced that all hybrids exhibit mixed intercalated/exfoliated morphology and that the extent of exfoliation increases with both clay amount and extrusion rate used. Moreover, it was pointed out that the silicate nano-scale dispersion significantly affects the crystalline morphology of copolyamide matrix, stabilizing the gamma-crystal phase, and the dynamic mechanical response of the hybrids, whose storage and loss moduli values result sensibly higher than those corresponding to the neat matrix. (C) 2003 Elsevier Science Ltd. All rights reserved