The effect of extrusion conditions on the dispersion of an organoclay in a polypropylene matrix
Résumé
Polypropylene-organoclay based nanocomposites were prepared via twin-screw extrusion. The effect of different processing parameters on the dispersion state was investigated. Complementary techniques were used to characterize nanocomposites microstructures. Scanning electron microscopy allows to quantify the remaining agglomerates, whereas X-Ray diffraction focusses on the intercalation of the clay platelets by the polymer chains. Rheological measurements in small amplitude oscillatory shear helps to characterize the nanodispersion of the organoclay. Dead-stop experiments were performed to follow the dispersion state along the screw profile. The results show that the screw speed plays a major role on the exfoliation, but a compromise has to be found between an efficient dispersion and the matrix thermal degradation. It also appears that both micro-and nanodispersion happens early along the screw profile, and that, in some conditions, the microstructure is established largely before the screw end.