Merci à tous pour votre participation au séminaire du Prof. João Maia!
Dispersion done (much) better: Harnessing extension in polymer blending and compounding
Prof. João Maia
Case Western Reserve University,
Department of Macromolecular Science and Engineering,
Cleveland, OH, USA
The dispersive mixing capability of twin-screw extruders (TSE) is hindered by the fact that standard kneading elements (KE) impose a shear-dominated flow and, thus, suffer from limited ability to effectively disperse highly viscous disperse phases, be they polymeric or solids, in a polymeric matrix. Extensional flows, on the other hand, suffer from no such limitations and are theoretically capable of providing much improved dispersive mixing. However, attempts to perform extension-dominated mixing in extrusion operations have been few and far in between, with decidedly underwhelming results.
In this seminar, a new type of extensional mixing element (EME) for single-screw extruders (SSE) and intermeshing TSEs will be presented and its efficiency in improving dispersive mixing significantly when compared, with nanoparticles of different geometries with standard two-lobed KEs will be demonstrated. In particular, we will show that the EMEs are highly efficient mixers for a number of systems, including immiscible and compatibilized polymer blends and polymer nanocomposites (0D, 1D and 2D). We will also demonstrate that by extending the EME concept to use in SSEs, it is also possible to significantly improve their dispersive mixing capability (a known shortcoming of SSEs), to the point the mixing levels become similar to those of TSEs equipped with standard KEs.