Effect of PVA saponification degree on internal structural changes in silica slurry during drying

This study examined the effect of adding polyvinyl alcohol (PVA) with varying degrees of saponification to an aqueous silica slurry on internal structural changes during drying using optical coherence tomography. During the initial stage of drying, the slurries began to agglomerate from the surface. Particle concentration in the agglomerated regions increased with higher saponification degrees of the added PVA. Considering the solubility of PVA and the hydrophilicity of the adsorption layer on the particles, the effect of saponification degree on the particle concentration in the agglomerated regions is attributed to variations in the electrophoretic mobility distribution and the thickness of the PVA adsorption layer on the particles. In the middle stage of drying, the magnitude of deformation in the agglomerated regions varied depending on the particle concentration and the thickness of the PVA adsorption layer. The dominant factors controlling the green density of the dried slurry were both the particle concentration in the agglomerated regions during the initial stage and the magnitude of deformation in these regions during the middle stage.