Gallery structure and exfoliation of organophilized montmorillonite:: effect on composite properties

Wyoming montmorillonite was organophilized to different extents with N-cetylpyridinium chloride and its gallery structure was studied by WAXS. PP nanocomposites were prepared using this silicate and their structure, as well as tensile properties were determined as a function of composition. Two peaks were observed in the WAXS patterns of some of the treated silicates, one of which disappeared during processing. The orientation of the organic compound in the galleries depends on its size and amount, as well as on the ion density of the filler. Multiple peaks appearing in the WAXS pattern of organophilized silicate may arise from interference, but they may also indicate the presence of several populations of layer distances. Water is absorbed between the galleries of partially organophilized silicates leading to the separation of the layers resulting in the appearance of new scattering peaks. Exfoliation occurs only above a critical gallery distance, which corresponds to the thickness of two aliphatic chains. Although exfoliation of the silicate is determined by its organophilization and gallery structure, composite properties are dominated by interfacial interaction. (C) 2003 Elsevier Ltd. All rights reserved.