Effect of a gradient in viscoelastic properties on the debonding mechanisms of soft adhesives

The effect of a composition gradient along the thickness in soft adhesive films was investigated. The adhesion properties of bilayer films made from acrylic solutions, one layer being more cohesive and the other more dissipative, were studied by performing probe tack experiments. To understand the mechanisms that determine the bulk and the interfacial contributions to the debonding, tests on different surfaces were carried out. The results show that the presence of a composition gradient can enhance the adhesive properties, particularly on a low-energy surface such as polyethylene. On steel, the presence of the thin layer of a more elastic adhesive in contact with the adherent can influence significantly the debonding mechanism, transforming the fracture from cohesive to adhesive.