RELATIONSHIP BETWEEN VISCOELASTIC AND PEELING PROPERTIES OF MODEL ADHESIVES - PART 1 - COHESIVE FRACTURE

The viscoelastic and peeling properties of polybutadiene/tackifying re sin compatible blends have been studied in detail. Viscoelastic proper ties have been described through the variations of the complex shear m odulus, G()(omega), as a function of frequency, omega and peeling pro perties through the variations of peeling force (F) as a function of p eeling rate (V). After showing the objective character of the peeling curves obtained, the variations of the peeling force and peeling geome try have been studied as a function of volume fraction of the tackifyi ng resin. In this first paper, the analysis is focused on the first do main of the Feeling curves, i.e. the cohesive fracture region. In this region, the peeling properties have been related to the viscoelastic properties in the terminal region of relaxation. It is shown that the longest relaxation time, tau(o), is a reducing parameter of the peelin g curves, so a peeling master curve-which is independent of temperatur e, resin volume fraction and polymer molecular weight-may be defined. Furthermore, the variations of the test geometry as a function of peel ing rate have been investigated: the variations of the radius of curva ture of the aluminium foil have been analyzed with respect to the visc oelastic behavior of the adhesive, which in fact governs the test geom etry. A detailed analysis of all these features leads to a model which allows one to calculate the peeling curves in the cohesive domain fro m the adhesive formulation.