Large strain rheology plays a key role in the peeling of a soft adhesive

Modeling the exceptional adherence properties of Pressure Sensitive Adhesives (PSA) from the material properties of the adhesive itself and from surface interactions remains a challenge. The presence of a complex debonding region where the adhesive undergoes cavitation and the very large strain of a spontaneously formed fibrillar network has defied many modeling attempts over the past 70 years. We present here the important insights made possible by the development of an instrumented peeling technique [Int. J. Fracture, 204, 175 (2017)], based on high resolution imaging of the shape of the debonding region during peeling. The fine characterization of the response of this fibrillar region allows a quantitative linking of the adherence performances in peeling with the extensional rheology of the adhesive, in agreement with a recently established model [Soft Matter, 11, 3480, (2015)]. This investigation opens the way towards the modeling of the fibril debonding criterion, which is the main missing link towards the prediction of the adherence properties.