Surface Segregation of PVA during Drying of a PVA-Water-Al<sub>2</sub>O<sub>3</sub> Slurry

Abstract

On the system of PVA-water-alumina, a new technique was developed to study quantitatively the surface segregation of PVA during drying of the slurry. This technique involves one-dimensional drying of slurry and determination of PVA content at various positions by sectioning. The samples containing 1.6 to 3.85wt% PVA were dried at 40° to 90°C. The drying temperature and the concentration of PVA affect the segregation markedly. With increasing concentration of PVA, the proportion of the constant-rate drying period to the entire drying period decreased. With increasing drying temperature, the proportion of the constant-rate drying period to the entire drying period decreased, and the surface segregation increased. The surface hardness increased with increasing content of PVA in the surface region. The surface segregation of PVA was discussed in terms of the behaviors of constant-rate drying, diffusion, and viscosity.