There are many test methods used to determine the strength of an adhesive including peel, shear, cleavage, and tension tests. Peel tests are common for tapes, labels, coatings, and other bonded materials. There are three main types of peel tests including 90 degree peel test, 180 degree peel test, and a T-Peel test. The Loop Tack test is similar in concept but is better classified as a tension test.
Why would you perform the T-Peel test instead of the 90 or 180 degree test? Well, the 90 and 180 degree tests are commonly used where a flexible material with an adhesive or other bonding method is adhered to a more rigid substrate. You would use the 90 over the 180 degree peel test if your flexible substrate can’t be bent cleanly back to 180 degrees. The T-Peel is used when both materials are either similar or both flexible.
The T-peel test requires that both of the bonded substrates are flexible. This means that they need to be able to be bent up to a 90 degree angle without breaking. Both substrates do not need to be the same material.