Infuence of solidification dynamics on the component distribution and particle orientation in polymer particle composites with flaky particles

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Incorporation of nanoparticles into a polymeric matrix is a way to modify material properties such as tensile strength, biocompatibility or optical properties. The functionality of these composites depends on the material selection and on the component distribution. The latter is strongly affected by the dispersion stability and interactions of the components as well as the process conditions during drying.In the previous research proposal the influence of the drying conditions on the component distribution was evaluated via cryoREM and Raman spectroscopy. Three different particle distributions were found: (i) particle enrichment at the substrate, (ii) even distribution of particles and polymer and (iii) particle enrichment at the free surface of the film. Additionally the component distribution during drying was modeled, taking diffusion of all components, drying and sedimentation of particles into account. As pivotal parameters the ratio of film thickness, drying rate, initial solvent content, particle size, density and the viscosity of the polymer solution was identified. These parameters could be summarized by non-dimensional numbers, by which the different distributions were mapped. These maps were validated with the experiments that were carried out. The established drying regime maps facilitate the paste design as well as the choice of drying conditions to adjust the component distribution in the drying and final film. The drying regime maps are so far limited to spherical particles. In many applications, however, flaky particles are used. The hypothesis for continuing the research project is that it is possible to establish drying regime maps also for flaky particles that predict the component distribution. An additional degree of freedom for flaky particles is the particle orientation. The particle orientation can play an important role for the functionality of the final film. Preliminary investigations show that the particles orient parallel to the substrate and free surface if they come close to it. Therefore, one assumes that a significant correlation of orientation and particle distribution. Aim of the proposed research project is to establish drying regime maps for flaky particles and their experimental validation. Additionally the orientation of the particles as function of the distribution will systematically be investigated.