Interfacial Fatigue Fracture of Pressure Sensitive Adhesives

Pressure sensitive adhesives (PSAs) have been rapidly developed in recent decades and have found their broad application in various fields including construction, electronics, biomedical engineering, and daily life. It is foreseeable that PSAs will be required to sustain prolonged static and cyclic mechanical loads in emerging applications such as soft robotics and stretchable/flexible electronic devices. However, the interfacial fatigue fracture of PSAs has not been studied. In this presentation, we report interfacial fatigue fracture of PSAs, i.e., the growth of an interfacial crack between a PSA and another material under prolonged cyclic loads. We synthesize a PSA with a highly sticky surface and a well-controlled bulk mechanical hysteresis. We conduct cyclic peeling tests and measure the interfacial crack growth with cycles. We identify a steady state after thousands of peeling cycles, where the crack growth per cycle is nearly constant. We plot this steady-state crack growth per cycle as a function of the applied energy release rate and find out the threshold for cyclic peeling. In parallel, we conduct monotonic slow peeling experiments to plot the crack speed as a function of the applied energy release rate. We compare the two thresholds for monotonic peeling and cyclic peeling and discuss the possible fracture mechanisms at the molecular and microscopic levels based on the experimental data. It is hoped that this study will provide new fundamental knowledge for fracture mechanics of PSAs, as well as guidance for future tough and durable PSAs.