Guillaume Normand

Matrix Degradation during High Speed Extrusion of Polypropylene/Clay Nanocomposites – Influence on Filler Dispersion

Abstract We prepared polypropylene/organoclay nanocomposites by melt blending in a twin-screw extruder, exploring the domain of high screw speeds (up to 1 100 min−1). The samples were characterized at both microscale (size of agglomerates) and nanoscale (level of exfoliation). We show that, despite a satisfactory exfoliation, the polymer matrix suffered important thermomechanical degradation by chain scission. We propose a way to correct this degradation on the viscosity curves and we confirm that high screw speeds are not necessarily favorable to clay exfoliation, essentially because of the too high melt temperatures encountered during the process.

Attempts to Optimize the Dispersion State during Twin-Screw Extrusion of Polypropylene/Clay Nanocomposites

Abstract Polypropylene/organoclay nanocomposites were prepared by melt-mixing in a twin-screw extruder. Polypropylene grafted with maleic anhydride was used as compatibilizer. The evolution of the microstructure along the screw profile was characterized through dead-stop experiments. In order to quantify the multi-scale dispersion state of the nanocomposites, different techniques have been used: scanning electronic microscopy (SEM) to observe the large remaining aggregates, X-Ray diffraction measurements to characterize the intercalation state by measuring the interlamellar distance, and finally rheological characterizations in the molten state to assess the dispersion state at the nanoscale. The effects of low barrel temperatures and high matrix viscosity were tested, in order to improve exfoliation by an increase in shear stresses.