This is the last in our series of common problems with common tests pertaining to adhesive materials. In this post, we will look at common problems associated with the ASTM D 1876 test method.
ASTM D 1876 is the Standard Test Method for Peel Resistance of Adhesives (T Peel Test). This test method is used to determine the relative peel resistance of adhesive bonds between flexible substrates utilizing a T-type specimen. The test specimen is loaded into a tensile tester with the bent, un-bonded ends clamped in the grips. The specimen is then pulled apart, and the peak and average peel forces are measured.
As with ASTM D 1004, the main challenge when testing to this method is sample preparation. Though no specific parameters or procedures for preparation are provided, it is important to follow all manufacturer instructions. Accordingly, it is essential that the adhesive manufacturer provides all relevant specifications for the application of the adhesive. These include surface preparation, mixing directions, application rate, and thickness and curing conditions.
If one or more of these specifications is not provided, it is important to document the parameters used so that the test can be repeated or used for comparison. Altering any of the sample preparation or test specifications can cause changes in the recorded properties. Because this method is generally used to compare the relative peel resistances of multiple adhesives, all specifications must be identical in order for the comparison to be valid.
Another important variable to consider is the backing material of the test panel. The backing material must be strong enough not to yield but also flexible enough to bend through the 90° angle of the test. If the backing material is too weak or too inflexible, undesirable failure modes may be observed. The presence of multiple failure modes adds difficulty when comparing the results of one test to another.
This blog post was adapted from a recent article by Amy Peterson, DDL Lab Manager, Products & Materials Division that appeared in the publication Adhesive & Sealants Industry (ASI).