Influence of Processing Conditions on the Preparation of Clay-Based Nanocomposites by Twin-Screw Extrusion

This review paper is devoted to the preparation of clay-based thermoplastic nanocomposites by melt blending in a twin-screw extruder. The influence of the main processing parameters (screw speed, feed rate, barrel temperature, screw profile) on the state of the clay dispersion at the micro- and nanoscale is characterized. The change of dispersion state along the screws and the corresponding mechanisms are presented. The interest of process modelling to predict the state of dispersion is evaluated and, finally, the main modifications of the twin-screw extrusion process to improve the clay dispersion are reviewed.

Preparation of Polymer-Clay Nanocomposites by Melt Mixing in a Twin Screw Extruder: Using On-Line SAOS Rheometry to Assess the Level of Dispersion

A prototype on-line rotational rheometer was fixed between a twin screw extruder and a multi-rod die of an industrial pelletization line used for the manufacture of polymer-clay nanocomposites. After diverting the required amount of melt to the device, measurements were performed in small amplitude oscillatory shear and used to estimate the level of dispersion of the organoclay in the polypropylene matrix, by means of correlations that are commonly utilized. The aim is to determine whether changes in clay type, clay content, feed rate and screw speed cause detectable alterations in the rheological response and thus in the level of dispersion, with a view to practical process monitoring and control. The analysis of the data is supported by XRD and electron (scanning and transmission) microscopy observations.