Effect of Highly Exfoliated and Oriented Organoclays on the Barrier Properties of Polyamide 6 Based Nanocomposites
Résumé
The influence of the incorporation of nanoparticles (organo-modified montmorillonite Cloisite 30B) in polyamide 6 (PA6) on the transport of small molecules was investigated. Nanocomposites were prepared by melt blending followed by cast extrusion for obtaining film-forming materials. The nanoclay content of the materials was varied from 0 to 5 vol%. Differential scanning calorimetry measurements, electronic microscopy, X-ray diffraction, and rheology were used for characterizing the nanocomposite structure. Because of the presence of nanofillers, a high barrier effect to nitrogen and water was clearly evidenced and mainly attributed to the increase of tortuosity because of the increase of the diffusion pathway generated by impermeable nanofillers. In this study, the high barrier effect was attributed to the very good dispersion of montmorillonite platelets in the PA6 matrix resulting from a two-step melt processing. This peculiar processing has induced a good exfoliation and an orientation parallel to the film surface of lamellar montmorillonite platelets which is clearly demonstrated from transmission electron microscopy analysis. The permeation results were evaluated on the basis of geometrical models proposed by Nielsen and Bharadwaj, and by analyzing the plasticization phenomenon in the case of water permeation involving a concentration-dependence diffusivity correctly approached by an exponential law.