Composite films based on polyamide 6 and lamellar unmodified alpha-ZrP nanofillers have been prepared for low filler amounts (less than 2 wt %) using cast process or blowing process. Whatever be the filler content and the film process conditions, the lamellar nanofillers were not intercalated by the polymer chains and micro-composites were obtained. On the other hand, the matrix crystalline structure highly depended on the presence of fillers and on the film process conditions. The nature of the crystalline phase and its orientation were shown to play a major role on the film barrier properties to helium. For instance, the presence of gamma crystalline phase associated to a specific orientation of the crystalline lamellae parallel to the film surface could significantly contribute to enhance barrier properties. This specific morphology was favored by the presence of alpha-ZrP in the formulation but depended also on the process conditions. (C) 2008 Wiley Periodicals, Inc.