Characterization of Clay-Polymer Nanocomposites

The functionality of the thermoset polymers also plays a vital role in the formation of exfoliated or intercalated composites [32]. The XRD studies reveal the exfoliation of clay platelets at all clay concentration except 10 wt% when dispersed in bi-functional epoxy resin [32]. Whereas the tri-and tetra-functional epoxy resin results in formation of intercalated nanocomposites only, except at very low clay concentrations. 

In polypropylene system, wide-angle XRD studies were carried out to analyze the effect of clay and compatibilizers on the thermodynamic stability of the monoclinic a-crystal of the PP. In general it was foimd that the monoclinic a-phase of PP is highly stable and not affected by the presence of compatibilizer or clays [ 15,21,28]. 

X-ray diffraction studies can give inference about the morphology of nanocomposite formation however, the evidence from the transmission electron micrograph can only confirm the state of dispersion of silicate platelets and the formation of nanocomposites. For analyzing in a transmission electron microscope, ultra-thin sections of 5 to 60 nm thickness should be cut from the nanocomposite samples imder ambient or cryogenic conditions using microtome. 

The clay remains as microtactoids (dispersed in microlevels) when it is dispersed in PP without the assistance of compatibilizer. By adding maleic anhydride grafted PP (PP-g-MA) as compatibilizer, well dispersed clay platelets are observed in the PP matrix. When polyolefin elastomer grafted maleic anhydride (POE-g-MA) compatibilizer is used, even two-phase separation has been reported between PP and POE-g-PP [15]. This phase separation is not identified in TEM analysis and it confirms the compatibility of clay and POE-g-PP. POE-g-PP enters into interlayer spacing and facilitates the delamination of clay layers. 

Transmission electron micrographs (TEM) can be used for both qualitative and quantitative analysis of silicate platelets dispersion. Han et al. 

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