Prediction of the morphology of heterogeneous plastic blends during single-screw extrusion

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Thermoplastics are processed in a wide range of converting methods. This potential is due to their low processing temperatures and their easy modifiability to achieve application-specific properties, e.g. by adding additives or functional components to generate blends. In plastics compounding and processing, homogeneity, i.e. the mixing of the components in the plastic melt, is the most important criterion for product quality. Distributive and dispersive mixing processes can be used to homogenize the polymer blends in the molten state. For this purpose, a wide variety of mixing elements are avail-able during compounding and processing by using single- and twin-screw extruders, which can con-trol the mixing efficiency. A major challenge is both the correct design of these mixing geometries and the selection of the as-sociated process settings, which in the end have a significant influence on product quality. For the design and improvement of the mixing geometries and the associated process settings, the numeri-cal simulation of plastic melts offers to significantly reduce these design steps. For this purpose, however, the elongation and shear deformations required for the homogenization of immiscible plas-tic blends must be simulated in order to be able to specify design criteria and process settings for dynamic mixers. This is where the research project comes in, by bundling and extending the know-how of the appli-cant's research unit for predicting the mixing efficiency of heterogeneous plastic blends. The aim is to develop a general model that describes dispersive mixing as a function of break-up and coalescence processes, taking into account the intensity of different types of deformation and adhesion promot-ers. This model should also take into account non-Newtonian viscous flow behavior. To this end, basic research must first be developed in order to obtain an advanced understanding of the droplet behavior in a plastic melt as a function of different types of deformation. A special Couette rheometer is to be constructed and various geometries investigated that induce different flow fields and thus different deformations in a plastic melt. Based on these results, the model will be developed and ap-plied and validated for realistic plastics processing operations in which the mixing zone of a single-screw extruder is simulated.