Unraveling the Relationship between Rate, Temperature, and Damage in Soft Adhesives. The Case of T-Peel.

Numerous adhesives have emerged in the past century, enabling advances in labels, packaging, wearable electronics, and flexible displays. However, understanding the interfacial fracture of these materials remains challenging due to difficulties in decoupling the contributions from irreversible bond scission (i.e., molecular damage) and internal molecular friction (i.e., viscoelasticity) to the total energy dissipation ahead of a crack.

This study aims to address this problem by quantifying the interplay between viscoelasticity and damage in 180^o peel tests. A series of acrylic adhesives were crosslinked with fluorogenic mechanophores, peeled at various rates and temperatures, and imaged with a confocal microscope to examine the extent of damage near their surface. Additionally, the viscoelasticity of each adhesive was assessed via linear rheology.

Our analysis reveals that the molecular damage in the adhesive is influenced by both rate and temperature, peaking near a Weissenberg number of 0.1. These findings are critical for the molecular design of advanced adhesives, as they challenge longstanding phenomenological theories of viscoelastic fracture by highlighting the coupling between viscoelasticity and damage in dissipating energy ahead of interfacial cracks.