The structure and rheological properties of a large number of layered silicate poly(propylene) nanocomposites were studied with widely varying compositions. Morphology characterization at different length scales was achieved by SEM, TEM, and XRD. Rheological measurements supplied additional information about structure. The results showed that these materials possess a very complex structural architecture. The introduction of functionalized polymer decreased the size of the original clay particles and improved their interaction with the polymer matrix. However, relatively large silicate particles were found also in composite samples yielding XRD traces without silicate reflection. XRD supplies information of limited value if the amount of silicate is low, the gallery distance of the stacks is large or their regularity is limited. On the other hand, XRD indicates intercalation well. Although exfoliated individual layers can be detected by TEM, the method cannot be used to draw general conclusions about the structure of layered silicate nanocomposites because of statistical sampling and bias. A large number of individual layers, i.e. large extent of exfoliation, led to the formation of a silicate network structure, which can be detected very sensitively by Cole-Cole plots of dynamic viscosity. We found that all four morphological entities (particles, intercalated stacks, individual layers, network) may be present simultaneously in the composites. The presence and relative amount must definitely influence composite properties. However, currently used experimental protocols do not supply sufficient information even to estimate the relative influence as well as interplay among different structural features quantitatively. We may conclude, however, that XRD and TEM alone are not sufficient for the characterization of nanocomposites with a complex structure.
- layered silicate nanocomposites
- silicate network
- poly(propylene) (PP)
- particulate structure