Influence of the drying conditions on the particle distribution in particle filled polymer films: Experimental validation of predictive drying regime maps

Particles are frequently incorporated into a polymer coating to tailor material properties. For coatings prepared from a dispersion of particles in a polymer solution, it is essential to understand how drying conditions and dispersion composition influence the component distribution during drying. In a companion paper, a model was developed to predict the particle distribution during drying. Three different distributions were found depending on particle sedimentation, diffusion, or evaporation being dominant: (i) particles form a sediment, (ii) equal distribution throughout the film, (iii) particle accumulation at the surface. In this work we report on experimental investigations of the transient and final component distribution. In the partially dried film the distribution was investigated using cryogenic scanning electron microscopy (cryoSEM) and in the dry film 3D micro Raman spectroscopy was applied. The transient distributions show all three regimes predicted by the model with some deviations. Investigation of the dry film reveals that these distributions are visible in the dry film, but with a less distinct gradient. Overall the agreement between the model and the experiment was good, indicating that the model predictions are valuable for the design of compositions and conditions for controlling particle distribution in polymer-particle composite films.