Temperature dependence of polymer crystalline morphology in nylon 6/montmorillonite nanocomposites

The influence of nanodispersed montmorillonite layers and process history on the crystal structure of nylon 6 between room temperature and melting is examined with simultaneous small- and wide-angle X-ray scattering and modulated differential scanning calorimetry. For the examined process history, nylon 6 exhibits predominantly alpha -phase behavior from room temperature to melting, with a gradual shift in chain-chain and sheet-sheet spacings from similar to 100 degreesC to melting. In contrast, the presence of aluminosilicate layers stabilizes a dominant gamma -crystal phase, which persists, essentially unmodified, until melting. The temperature dependence of the total crystallinity and the relative fractions of alpha- and gamma -phases is strongly dependent on the layered silicate content and the interaction between the nylon 6 and the aluminosilicate layers. Additionally, the temperature dependence of the alpha- and gamma -phases imply that the gamma -phase is preferentially in the proximity of the silicate layers, whereas the alpha -phase exists away from the polymer-silicate interphase region: In general, process history and use-temperature will determine the relative fraction of the crystalline polymer phases in semi-crystalline polymer nanocomposites, and thus have significant influence on the stability of the crystalline region at elevated temperatures. (C) 2001 Published by Elsevier Science Ltd.