In order for your glue to perform properly, it must be able to penetrate (or "wet") your substrates. Some substrates are more difficult to penetrate than others. This is a result of varying surface energies.
LD Davis - BLOG
Dyne Levels play a major role in proper adhesion, and here is why:
The Dyne Level of a material is called its surface energy. When glue is applied to a substrate, its “wettability” is impacted greatly by its surface energy and that of the substrate.
If you work in the rigid packaging industry, you know how important it is for your glue and substrates to work seamlessly together. Most times, this is the case. But, let’s say you’re working with a new client that has a very specific package design in mind and their substrates are a lot tougher...