Rubber toughening of polyamide 6/organoclay nanocomposites obtained by melt blending

Rubber toughening of polyamide 6 (PA6)/layered-silicate nanocomposites was investigated. Different systems were prepared via melt blending according to different formulations. Wide-angle X-ray diffraction and transmission electron microscopy analyses showed that the nanocomposites had an appreciable degree of exfoliation. A linear elastic fracture mechanics approach was applied to characterize the material fracture behavior in dry conditions, whereas, because of the considerable ductility exhibited by the samples in the wet state, an elastic-plastic approach based on the essential work of fracture methodology was employed. In the absence of rubber, the presence of silicate layers makes the material fracture resistance decrease relative to neat polymer, depending on the degree of humidity. The results showed that the toughening action of rubber strongly depends on the degree of humidity of the material, at least for the rubber contents considered in this study (lower than 10 wt %). In particular, in slightly wet conditions, it was found that the addition of small amounts of rubber increased the fracture resistance of PA6/layered-silicate nanocomposites without appreciably impairing the material stiffness. Thus, the results indicated that, for the given humidity conditions, a good balance between stiffness and toughness was obtainable by employing a suitable ratio of rubber to layered-silicate content. (c) 2006 Wiley Periodicals, Inc.