Adhesion = System

Adhesion is a property of the system

The implication of the "Measurement is tricky" page is that adhesion isn't some objective part of a joint. instead, Adhesion is a property of the system. Therefore adhesion depends on lots of things such as:

  • Temperature
  • Time
  • Speed
  • Direction
  • Relative moduli
  • Surface dissipation
  • etc. etc.

This is not what most of us want to hear. We want simplicity. But we can't have it, so embrace the systems approach and much about adhesion starts to become much clearer.

In particular, embrace WLF - tTE - tTS, Williams Landel Ferry, time Temperature Equivalence or time Temperature Superposition (they're all the same thing) which helps you work out how strong your bond will be at a different temperature or (equivalently) a different test speed.

See why peel, lap and butt joints of the same adhesive system give very different values for adhesion. Embrace things like Kaelble peel to understand what is going on in an apparently simple peel test or the fearsome (until I translated it into a friendly app) Goland-Reissner lap joint analysis. Find out why 4-point bend tests are much trickier than you might think.

In short, explore the testing section to see why things are complicated - and make sure you use the information to your advantage. By not getting trapped into thinking that adhesion is something that depends on just one factor you will find that adhesion makes much more sense. And for those who want to compare surfaces and treatments, start to think in terms of Adhesibility, using JKR-style thinking combined with your favourite AFM or Nanoindenter.