A “wetable” surface is said to have “high surface energy,” liquid can spread across the substrate without the bunching of droplets. Low surface energy materials which do not “wet out” leave liquid droplets standing proud – imagine a freshly waxed car sprayed with water droplets – the drops bunch up at a steep angle to the paintwork.
Surface energy is normally measured in mJ/m² or Dynes. Generally, to be able to bond a material, it needs to be >36 mN/m. However, this can still be pretty hard to bond to, even with industrial adhesives.
Table showing surface energy values of common engineering materials. Figures in mJ/m².
As you can see, plastics exhibit the lowest surface energy. This makes them challenging for both industrial adhesives and printing inks to adhere to.
There are three ways to bond.
For further information or technical advice, please contact Permabond’s helpline team.