Experimental investigations of the morphology and the morphology formation of levitated single-particles as a model system for reactive and non-reactive spray processes

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Spray polymerization is a comparatively new method for the production of polymer powders. In this process, polymerization, particle shaping, morphology formation and drying is carried out in one single process stage. Since the control of these processes is limited, the acoustic levitation, which enables the contactless positioning of droplets, is applied as a model system for spray processes. In this set-up, comparable conditions of reaction and drying are realized, especially by considering the relative velocity between droplet and gas phase. During the first funding period, the acoustic levitation was proven to be an adequate model system for spray processes. The morphology formation, as well as the drying- and reaction kinetics of different reaction systems were investigated under stationary and non-stationary conditions. The aim of this subsequent application is, basing on the up to now obtained results, observing the morphology formation of the particles in several reactive and non-reactive systems depending on different operating parameters. Afterwards, appropriate phase diagrams of the morphology are supposed to be developed. In the end, a basis is supposed to be built up in order to control the morphology selectively and verified exemplarily. In this context, the regulation of morphology is considered as well in cooperation with Prof. NIEKEN (modeling of morphology formation) and Prof. SIMON (fast online- image analysis). For that purpose, the ability of observing the particle morphology during the second drying phase is supposed to be improved by combining the video image analysis with the optical weighing of levitated droplets. In this way, monitoring the porosity, for instance, can be enabled. Different investigations on the second drying phase are planned as well, since it was observed that the polymer phase composition do have a particular influence on the morphology formation during the second drying phase. This influence is planned to be quantified and included in the modeling I cooperation with the research group of Prof. NIEKEN. Subsequently, emulsion polymerization as a heterogenic system is supposed to be investigated as well. Besides the parameters such as temperature or monomer composition, there are factors like the emulsifier concentration which influence the reaction- and drying kinetics as well as the morphology. For the production of tailored polymer powders, the knowledge about these factors is needed. In order to confirm the robustness of the acoustic levitator as a model system, drying processes and polymerizations are supposed to be carried out in a spraying tower under equal conditions.