PSTC (Pressure Sensitive Tape Council) and ASTM (American Society for Testing and Materials) are helpful adhesive test methods to test or evaluate adhesive tapes. These tests are important in order to find the right product for your application. The most common performance measures are Tack, Peel, and Shear Adhesion. All these adhesion properties such as tack, peel strength, and holding power become handy control tests. PSA is a little tough and it’s not easy to find a specific product fit for project/application. But all these components become an important tool for quality departments.
The 4 primary reasons for testing products are Product Development, Quality Assurance, Product Change and Problem Solving. The most common factor in the need for testing is either trying to prevent a failure or find a solution for failure and making it successful. There are various reasons why bonds fail, not only due to the PSA adhesives but other reasons like the use of right product, Surface Prep, or Processes: -
For all these situations, standard test methods are used for the starting level. Quality assurance test methods follow these standard procedures to provide comparison data. The most common pressure-sensitive adhesive test methods are: - Tack, Peel Strength, and Shear Adhesion or Holding Power.
Tack: -This test is for determining the adhesion of an adhesive to a surface or you can say measuring the ability of a tape to make a permanent bond during the initial contact of an adhesive with the substrate without any external pressure. This test is for measuring the aging on the tape. A sample of an adhesive is applied on the substrate and weight is added. Then sensors will measure the peel of tape time. This procedure is completed under several temperature conditions to determine the aging of the tape. There are different ways to measure the tack level according to the application. Loop tack, and rolling ball tack are the common tests for tack tests. In the Loop Tack test, a loop is created with the PSA material to contact the substrate and then ends are clamped together in an upper direction. Loop is pushed onto the surface, compressing adhesive. And, the loop is pulled up and debonds from substrate. Rolling Ball tack is sensitive to set-up variation and finds the best quality assurance for determining the process issues. The Rollin ball test also provides information on softness as distance is inversely proportional to thickness and softness.
Peel Adhesion: - The Peel Adhesion test is specifically to measure the adhesion of the tape. This test is to evaluate the force required to peel off the pressure-sensitive tape from the testing panels (any material/substrate). In this test, a tape sample is applied onto a specific surface with a defined amount of pressure. And, keeping it as it is for a controlled time period. After that time period, the tape is peeled off with machines in order to measure the force needed. This test is a good indicator of relative adhesion strength from one tape to another.
Shear Adhesion Test: - This is the standard test for examining the cohesive strength of an adhesive. In this test, samples are applied with loaded weights on test panel. Then peel-off time is measured by the sensors. This test is performed under several temperature conditions. If an adhesive failure occurs, then this test will become more of a holding power test.
ASTM test standards, 2 most common tests under these standards: - ASTM D3330-04 – the standard test method for peel adhesion of PST, and ASTM D3359-22 – for measuring adhesion. Please see the information below for these 2 tests as what these tests are, why and when we do these tests and procedures to do these tests.
ASTM D3359-22 is a standard test method measuring the adhesion by tape test. In this test, the adhesion of coating films applied to metallic substrate and removal of PST over the cuts made on the film. Under this test method we are using 2 test methods:
Both of these tests are considered as the variants of tape and peel test. The crosscut test is considered to be unsuitable for thicker films than 5mils.
ASTM D3330-04 covers the measurement of peel adhesion of PST. This test includes 6 test methods depending on specific test and test type used for determining the adhesion of PST. See below all six test procedures: -