How to improve peel strength in adhesives?
Last update on Jan 14, 2026
Peel strength testing determines the adhesive strength of materials that have been bonded together. The materials are peeled apart at a constant speed and the strength of the force needed to separate the materials is calculated along with the width of the bond surface to determine the peel strength. Typically, tests involve peeling two flexible materials that have been bonded to each other, or one flexible bonded material adhered to a rigid substrate1.
Peel strength is the average load per unit width of bond line required to separate bonded materials where the angle of separation is 180 degrees. Peel strength testing is often used to characterize the bonding strength of tape, adhesives, and flexible substrates, such as rubber, films, biomaterials, consumables, medical packaging and more. There are many different peel testing methods to choose from, depending on the materials used2.
Typical graph showing a peel strength test (Image credits: AMETEK2)
How is shear strength different from peel strength?
Both peel strength and shear strength involve applying a force to a bonded joint but the key distinction lies in the direction of the applied force2.
In peel strength, the force acts parallel to the bond line, trying to separate the bonded surfaces in a peeling motion (like peeling an orange). In shear strength, the force acts parallel to the bond line as well, but it tries to slide the bonded surfaces laterally against each other (imagine trying to slide two pieces of wood glued together sideways).
| Strength type | Force direction | Failure mode | Example application |
| Peel strength | Parallel to bond line (separating) | Lifting or peeling of one adherend from the other | Adhesive tape, labels |
| Shear strength | Parallel to bond line (sliding) | Lateral sliding of one adherend relative to the other | Structural bonding, furniture joints |