Abstract
A simple tack-evaluation technique of adhesion properties between soft materials was developed, where two soft materials with uniform thickness adhered on cylindrical glass sticks were placed in a crossed-cylinder geometry and formed a point contact. The notable features of this technique were that the shape of contact surface was circular and that the contact radius of interfacial boundary continuously changed in all processes from press after contact to separation. The adhesion properties between the hydrogels which were consisting of partially neutralized poly (sodium acrylate) and physically cross-linked by Al3+ ions (PSA gels) have been extensively studied with the use of this technique. In this paper, the effects of the degree of neutralization and the addition of hydrophilic fumed silica on adhesion properties of PSA gels are presented. The adhesion force and the separation energy depended on the degree of neutralization or the amount of fumed silica. The results were discussed in terms of the molecular interaction in the surface and the elastic and viscous properties in the bulk network on the basis of the measurements of Fourier transform infrared spectroscopy and dynamic viscoelasticity.
