ABSTRACT
Th e adhesive and mechanical (rheological) properties of viscoelastic polymer materials are time dependent.1 Th ese properties come into play when the material is deformed in compression2 in the course of adhesive bond formation or when it is deformed during detachment. Both stages require an input of energy. Under an applied force, part of the energy input is irrecoverably dissipated through a mechanism of viscous fl ow, whereas another part is stored and can be released elastically upon removal of the bonding or detaching force.3-5 Th e dissipation never takes place instantaneously.6 As a result, the response of an adhesive material lags behind the application of a deformation force. For this reason, adhesive properties are time dependent and this dependence cannot be ignored when dealing with such materials. Although the mechanical properties of pressure-sensitive adhesives (PSAs) are the subject of extensive study and have been reviewed in relevant books,7,8 as well as in earlier chapters of this book, the signifi - cance of relaxation properties for pressure-sensitive adhesion are still not adequately understood.9
