Influence of Particle Shape on the Drying Regime Maps for Platelike Particle-Polymer Composites

In previous works, the influence of drying conditions on the particle distribution in filled polymer films was investigated using spherical silica particles and polystyrene pellets. The results showed that changing drying conditions can influence the particle distribution in a dry film. These were summarized in drying regime maps to predict the distribution of the particles in the final film; the particles accumulate at the top of the coating (evaporation regime) or sink to the bottom (sedimentation regime) or remain homogeneously distributed (diffusion regime). In the present study, the particle geometry was oblate to determine the changes in the particle distribution in comparison to spherical particles. A simulation was developed by changing the sedimentation and diffusion models. Concentration-dependent sedimentation rates and the particle orientation in the dry film were experimentally determined. New drying regime maps were plotted and compared. The simulation results show an expansion of the diffusion regime for the platelike particles in comparison with spherical particles. The regime maps were validated using platelike glass particles dispersed in poly(vinyl alcohol) (PVA) with water. The particle concentration profiles in the dry film and the film morphology were obtained via three-dimensional (3-D) Raman spectroscopy.