Standard Test Method for Peel or Stripping Strength of Adhesive Bonds
The procedure described in ASTM D903 is a 180 degree peel test. Unlike ASTM D1876, where the tape is peeled from a flexible backing, D903 is peeled from a rigid subtrate. Most pressure sensitive adhesive tapes exhibit their full peel strength when peeled at this maximum angle of 180 degrees.
Tape specimens are usually 1 inch in width and 12 inches long. Most of the tape is secured onto the rigid subtrate backing and the other half is attached to the grip. Technicians may also use a leader to attach the adhesive tape to the grip to help with securing the sample.
Vise grips are the most common and economical solution for testing ASTM D903. Rubber grip face inserts are typical for testing tapes, however heavier duty fiber backed tapes may need serrated grip faces or potentially a wrap grip. Pinch grips are also a great option especially for thicker, reinforced tapes.
Along with the grips, the test also requires a substrate backing. A stainless steel plate is the generally accepted standard, however other materials such as wood, plastic, or plaster board, may be used. The plate must be slightly thicker than the tape and be free of any scratches or defects. Frequent cleaning is also required to keep the plate free of any adhesive residue.
Universal Grip has designed an easy to use 180 degree peel fixture. The substrate can be easily interchanged between metal and glass. The Galdabini Quasar 2.5kN machine is great for advanced peel testing in both quality control and R&D environments.
The critical calculation is average peel strength which is taken from the middle of the data for each test. Multiple tests can be grouped together into a lot to calculate an average value.