Swelling Kinetics of Hydrogel Beads in Aqueous Glycerin Solutions

Abstract

This study examines the swelling kinetics of polyacrylamide hydrogel beads in aqueous glycerin solutions of differentconcentrations. The total absorbed mass of the hydrogel beads remains nearly constant, independent of glycerin concentration, butthe swelling process is markedly slower with increasing glycerin concentration in the aqueous solutions. Absorption capacity curvesexhibit universal kinetics when time is rescaled using a characteristic time proportional to the viscosity of the solutions. Additionally,a novel visualization technique is employed to observe the core−shell structure of the hydrogel beads at early times in the swellingprocess. The evolution of the core−shell structure indicates a constant front velocity, which also reveals universal behavior with thesame nondimensional time, suggesting a viscous dominated transport of the solution penetrating the beads.