Chapter 6: Strong Adhesion with Weak Polymers

The classic strong adhesives are basically strong solids with sufficient entanglement to dissipate crack energy. Adhesive tapes, as simple observation tells us, achieve strong adhesion via weak, easily stretched polymers, achieving the same goal of dissipation by very different means. These PSAs (Pressure Sensitive Adhesives) are tricky to explain because their strength depends on many factors such as the temperature of the tape, the speed at which you pull it, the roughness of the surface (smoother is stronger), the nature of the surface and the time spent in contact. But it's worth the effort to understand them because you can better determine which tape will work best under which conditions, and why some of them peel off cleanly and others leave a residue. You might even gain some sympathy for supermarkets who have to provide “easy peel” packaging with zero failures before peeling, easy peeling when required and the absolute minimum of plastic involved. One mystery remains: how silicone release liners for tapes work. Spoiler alert: it's not because of their low surface energy. We need to wait till Chapter 10 to find out.