Low interfacial fatigue threshold prevails in various pressure sensitive adhesives

Pressure sensitive adhesives (PSAs) are made of viscoelastic polymer networks in their rubbery phase. They form strong adhesion to various materials within seconds under fingertip pressure, without additional chemical or physical treatments. Over the years, PSAs have been widely used as load bearing tapes in various applications. The expanding application domain of PSAs has raised a critical need for their enhanced fatigue resistance: while conventional applications such as duct tapes involve mostly static loads, new applications require PSAs to maintain their adhesion under prolonged cyclic loads throughout lifetime. However, despite their rapid development, the fundamental mechanics and polymer physics of fatigue in PSAs under cyclic loads have remained poorly investigated. In this presentation, we experimentally investigate the interfacial fatigue fracture of various PSAs, including the commercial heavy-duty shipping tape and 3M VHB tape, as well as homemade materials with tunable bulk hysteresis. We measure the interfacial fatigue threshold, below which a crack does not propagate under cyclic loads. We show that a low interfacial fatigue threshold, on the order of 1-5 J/m², prevails in various PSAs. The measured threshold agrees well with the theoretical prediction of a modified Lake-Thomas model that considers noncovalent bond breaking at the interface. Finally, we discuss possible additional dissipation mechanisms involved in crack propagation processes beyond the threshold.