Peel or adhesion testing is the measurement of the adhesive or bond strength between two materials.  It is performed by applying a tension load to the materials on one of three different ways:
 
Pulling two flexible materials axially away from each other forming what is called a 'T' peel
 
Pulling a flexible material away from a non-flexible material or substrate, both held vertically, forming what is called a 180 degree peel
 
Pulling a flexible material away from a non-flexible material or substrate, which is held horizontally, forming what is called a 90 degree peel

For example separating the backing from an adhesive bandage would be a 'T' peel, pulling the back of a blister pack of tablets would be either a 90 degree or 180 degree peel and pulling the seal from the top of a yoghurt pot would be a 90 degree peel.  There are varying degrees of flexibility and shapes creating a wide range of variations of these three basic peel types, requiring a variety of test grips and fixtures.

Benefits of Peel/Adhesion Testing

Ensuring the integrity and safety of products
Ensuring the proper functioning of adhesive seals e.g. openability
Reducing material costs and achieving lean manufacturing goals
Compliance with industry standards


Standards

A number of standards for testing adhesives seals ad bonds have been developed, such as:
ASTM D1876 - 08 Standard Test Method for Peel Resistance of Adhesives (T-Peel Test)
BS EN 1895:2001 Adhesives for Paper and Board, Packaging and Disposable Sanitary Products.  180 Degrees.  'T' Peel Test for a Flexible-to-Flexible Assembly
ISO 11607-1:2006 Packaging for Terminally Sterilized Medical Devices - Part 1: Requirements for Materials, Sterile Barrier Systems and Packaging Systems
ISO 11339:2003 Adhesives - T Peel Test for Flexible-to-Flexible Bonded Assemblies