Structure and mechanics of soft PSAs (pressure sensitive adhesives)

The adhesive performances of a PSA (Pressure Sensitive Adhesive) are attributed to their viscoelastic properties. In this paper we analyse the viscoelastic behaviour of different PSAs having substantially similar adhesive performance. Linear and non linear analysis were performed using small amplitude oscillatory shear tests and tensile stress-strain tests, respectively. However, deeper knowledge can be achieved by non linear viscoelastic tests. Modelling of tensile stress-strain curves is proposed, based on a network theory accounting for the presence of entanglements, but a rate-dependence of some of the physical parameters of the model is introduced in order to describe correctly experimental data. It is shown that the same substantial in-service properties can be achieved with adhesives showing different fingerprints in terms of viscoelastic spectra.