Adhesion Depends on Interfacial Strength: Time and Temperature Effects

High Resolution Image Download MS PowerPoint Slide In the conventional description, peeling of an adhesive from a solid substrate is expressed in terms of adhesion energies at adhesive-substrate interfaces. However, this energy-based perspective faced considerable difficulties in explaining why the adhesion energy, also known as peel strength Γ p, is many orders of magnitude greater than Dupré’s thermodynamic work of adhesion, Γ 0 . In this study, we present experimental evidence to demonstrate that polymer adhesion is governed by interfacial strength σ interf, defined by the pair of adhesive and substrate. A tensile adhesion test is performed to estimate σ interf from adhesion strength σ adh equal to the engineering stress at detachment. This test stretches, at various rates under different temperatures, one end of a ribbon-like specimen with the other end adhered to the same substrate used in peeling tests until adhesive detachment. The dependence of σ adh on applied rate and temperature is found to be the same as that of Γ p from conventional peeling tests on peeling speed v p and temperature. Our stress perspective shows that Γ p explicitly correlates with σ adh through a characteristic length scale P instead of Γ 0 . Here, P is the distance from the peeling front, beyond which the adhesive undergoes little deformation. Since P is a much larger length scale than a molecular scale and σ adh directly depends on polymer–substrate interfacial interactions, Γ p explicitly depends on σ interf . As activated processes, in both peeling and tensile adhesion tests, interfacial debonding on shorter time scales and lower temperature required higher interfacial stress.