Epoxy-clay nanocomposites: Morphology, moisture absorption behavior and thermo-mechanical properties

The morphology and moisture barrier characteristics are studied of epoxy-based nanocomposites reinforced with layered silicates. Two different types of organoclay, including the octadecylamine modified montmorillonite (BOP) and the quaternary alkylamine modified montmorillonite (KH-MT), were studied. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated the fonnation of intercalated nanocomposite for the KH-MT system, while intercalated/ordered-exfoliated nanocomposite for BOP system. The moisture absorption behaviour was different for different organoclays: the moisture absorption rate was similar for the neat polymer and the KH-MT system, which could be fitted to the Fick's second law. The moisture absorption rate of the BOP system was much lower than the two systems, which was predicted using a non-Fickian model based on the 1D Langmuirian solution. The deviation from the Fickian diffusion for the latter system is associated with exfoliated morphology and more unifonn dispersion of clay particles, which altered the diffusion path of water molecules in the nanocomposite. The moisture diffusivity of nanocomposites in general decreased with increasing clay content, the reduction being more pronounced for the BOP system. Moisture-induced thennomechanical properties changes for these two nanocomposites were studied as well.