The peel strength is the measure of the average force to part two bonded materials like tape, labels, textile or plastic films. The strength is calculated during a peel test at a constant speed rate by divided the average force required during the test by the unit width of the bonded samples. Depending on materials, norms, products, the tests can be done with different angles: 90° and 180° are commonly used.
The peel tests can be performed on containers such as jars, cans, trays, yogurt, applesauce or pockets and pouches. In this case, tests are available at different angles which can be close to the product use. Peel test at 45° for example.
Depending on the type of test, we can use different accessories:
- Peeling table for packaging
- Rolling fixture for high forces and in the case of a material bonded to rigid as the carpet on wall or floor
- Wheel for adhesive tapes
Like friction, peeling is a discontinuous phenomenon: there is a peak and then a plateau with saw tooth. This is the start peak which is generally used to characterize the peel strength.
In the case of adhesive materials, we don't use the first peak, we measure the average force during the test divided by the width of the sample, we obtain a resistance value in N/mm.
Video of a peel test at 45 ° on an applesauce container:
Typical curve of the peel test of this video: There is a first peak corresponding to the force to begin opening the can. Then a tray with small variations which corresponds to the seal coat. Finally a last peak corresponding to the force required to detach the end of the cap.
Some other types of peel tests:The most conventional peeling test is performed at 180° but different mounting systems exists to allow testing at 90° and adjustable angle. Some of these systems are presented below:
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