Adhesion properties of swollen hydrogels evaluated by a point‐contact method

Abstract The adhesion of swollen hydrogels was studied with the use of a simple tack‐evaluation technique using a point contact in the air at room temperature. The hydrogels used here were poly(sodium acrylate) gel physically crosslinked by aluminum ions. The adhesion properties were examined under different experimental parameters, i.e., separation velocities, normal loads, and waiting periods prior to separation. The effects of the material parameters resulting from the different degrees of the crosslinking on the adhesive properties were also examined. As a result, the adhesion force and the separation energy showed a power‐law behavior with different powers, which depended on the experimental and material parameters. The adhesion properties were determined by the bulk viscoelasticity as well as the surface physical and chemical properties. The results were discussed in terms of the surface molecular interaction and the bulk viscoelastic and viscous properties on the basis of the measurements of the apparent contact area, the ATR FTIR spectrum, and the dynamic viscoelasticity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007