Evaluation of the structure and dispersion in polymer-layered silicate nanocomposites

Polymer-layered silicate nanocomposites have drawn a great interest in polymer science these past years. Understanding of the complex mechanism of dispersion and exfoliation of the clay tactoids may allow us to better control the final morphology and the homogeneity of clay nanocomposites and thus their macroscopic properties. The first step we propose in this study consists of a multiscale approach of the exfoliation state of the extruded polypropylene/montmorillonite nanocomposite. We used three extruders designs: a single-screw extruder, a twin-screw extruder, and an optimized-screw extruder with adapted shear. The rheological analysis, the WAXS diffractograms, and the TEM micrographs all show different nanocomposite morphologies. A statistical TEM image analysis methodology was developed to evaluate the different particle parameters (thickness, length, aspect ratio, interparticle distance). The results obtained show a correlation between the size of the tactoids and the shear intensity.