Search for a command to run...
In the conventional description, peeling of an adhesive from a solid substrate is characterized in terms of adhesion energies at adhesive-substrate interfaces. However, this energy based identification faced considerable difficulties in explaining why the adhesion energy, also known as peel strength /gammap, is many orders of magnitude greater than Dupré's thermodynamic work of adhesion, sigma0. In this study we present experimental evidence to demonstrate that polymer adhesion is governed by interfacial strength formed between the adhesive and substrate whose surface energy /gammas plays no explicit role in controlling the adhesion strength /sigmaadh. On different substrates with widely varying surface energies, by carrying out both tensile-adhesion tests to demonstrate the dependence of /sigmaadh on applied rate and temperature and conventional peeling tests to show the effects of peeling speed vp and temperature on /gammap, we propose that /gammap explicitly depends on /sigmaadh through a characteristic length scale P instead of /gammas and /gamma0. Here P is the distance of the adhesive layer away from the peeling front, beyond which the adhesive undergoes little deformation. Since P is a much larger length scale than a molecular scale and /sigmaadh directly depends on polymer-substrate interfacial interactions rather than substrate surface energy, peel strength /gammap has no relationship with /gamma0 and its dependence on temperature and peeling speed stems from the time and temperature dependencies of interfacial strength /sigmaadh. As activated processes, interfacial debonding on shorter time scales and lower temperature required higher interfacial stress. Consequently, /sigmaadh is rate and temperature dependent.