In-line optical characterization during extrusion of polymer blends

The assessment of morphological development during the extrusion of small amounts of high-valued polymer-based systems is critical for understanding the processability of new plastics and for monitoring the extrusion of complex formulations. However, reports on the structural development during the extrusion of industrial plastics, measured by means of in-line optical techniques, are still scarce. In this contribution, we present a single / twin-screw mini-extrusion system of modular construction, with well-controlled outputs in the range 30-300 g/h, coupled to an optical slit die able to perform small angle light scattering (SALS) and polarized optical microscopy. The optical validation of this small scale device was performed using optical standards dispersed in a PDMS matrix. The output of this validation is the presentation of an operational window mapping the range of particle sizes and concentrations that can be measured with the two complementary in-line optical techniques. The techniques were then used to study the morphological development in extruded PS/PMMA industrial blends. We will present the in-line characterization of droplet orientation, deformation, coalescence, structuring during extrusion, relaxation processes upon cessation of extrusion, as well as the limitations of the techniques for characterizing industrial blends.Portuguese Foundation for Science and Technology through the Strategic Project LA 25:2011-201