The use of on-line characterization technologies during the manufacture of nanostructured materials

Abstract

Since their potential has become widely recognized, one of the major research lines on polymer-clay nanocomposites has focused on the preparation of well dispersed systems, which involves investigating their compounding (including their structural and morphological characterization) and the determination of their physical and mechanical performances. Currently, there is an understanding that a high degree of dispersion, particularly exfoliation, of the nanoclay is required to improve the overall performance. Although the influencing parameters are known – interfacial adhesion, chemical affinity and operating conditions – the effect of each on the onset and extent of the organoclay dispersion are still subject of debate. Twin screw extrusion allows for control of the main variables (shear, stress and time), but also, due to the typical modular construction, offers a high degree of freedom in creating the adequate screw design and enables knowledgeable alteration of the barrel. These features offer a solid basis for the development and implementation of apt on-line/in-line monitoring techniques, able to follow up the evolution of dispersion of polymer-clay nanocomposites during processing. This research included the validation, implementation and application of a methodology based on inline Near-Infrared (NIR) Spectroscopy for the characterization of the dispersion along the extruder axis. The results showed that the operating conditions have great impact on the dispersion level, but also that degradation may affect the interfacial chemistry of the system, altering the dispersion pathways. Overall the results obtained confirm that NIR is a valid tool for the on-line characterization of these materials, offering the possibility of assessing in real time the clay dispersion, enabling proper corrective and optimization actions over the material characteristics in a timely manner