Understanding the role of crosslink density and linear viscoelasticity on the shear failure of PSAs

Pressure-sensitive-adhesives (PSAs) are ubiquitous in electronic, automobile, packaging, and biomedical applications due to their ability to stick to numerous surfaces without undergoing chemical reactions. These materials date back to the 1850s but their resistance to static shear loads remains challenging to predict from molecular design. In this talk, we will discuss the role of crosslink density and linear viscoelasticity on the shear failure of PSAs. The key result is that crosslinking acrylic PSAs with a metal chelate like Al(acac)₃ leads to notable stress concentrations ahead of the peel front, as well as a transition from bulk to interfacial crack growth. The shear stress distributions, as evaluated by means of a linearly viscoelastic shear lag model, suggest that this transition is related to the evolution of ratio of the load transfer length to the bond length as dictated by the mechanical properties of the backing and adhesive layers, and the tape geometry.