'Peel adhesion' is an industry-standard test material manufacturers do to understand how sticky the adhesive is.
There are various tests used to evaluate adhesive strength; this image shows three ways to test glue:
Manufacturers apply a piece of sticker material (also known as media) to a galvanised steel surface. It's then left for 24 hours (usually) before peeling off at varying angles. The amount of force it takes to peel the media is known as the 'peel adhesion'.
The angles of the test are typically either 90 or 180 degrees to test the adhesive in different conditions that may represent the real world.
Makers of self-adhesive vinyl conduct these tests in laboratory conditions on machines that look like this:
The force required to peel the media away defines how strong the adhesive is.
Here is a list of the forces required and the 'category' of adhesive-strength it falls into:
- Removable adhesive = less than 19 N/25mm
- Permanent adhesive = 20-28 N/25mm
- High-tack adhesive = 29 N/25mm and up