Today we are look at the ASTM D 3759 test method as part of our continued discussion on common problems that can occur with some common industry standards, and how these factors can be minimized and eliminated.
ASTM D 3759 is the Standard Test Method for Breaking Strength and Elongation of Pressure Sensitive Tape. This test method can be used for comparison purposes and can also provide information for material specifications for product design and quality assurance applications. The results derived from this standard provide information regarding the relative strength of the as-received tape and can assist with characterizing backing materials.
Like ASTM D 3330, choosing the correct test procedure is a consideration for this test standard. The test procedures and parameters change depending on the expected elongation, pull direction and whether or not the tape is reinforced with filaments. If proper attention is not paid to the procedure, inconsistent test results will occur.
Like many other adhesive tests, sample preparation is the major area to pay attention to prior to testing. Preparing samples in a given direction (e.g., machine vs. cross) can yield vastly different results, depending on the backing material. Attention must be paid to the directionality of the tape when preparing the samples, or they could be confused.
Sample conditioning also plays a role in testing. Excessive temperature and humidity can affect adhesives and backing materials. For example, if a paper backing is exposed to high humidity, the water absorbed in the paper can cause a decrease in breaking strength. Over-handling of the test specimens can also cause localized heating of the sample.
During testing, it is important to monitor and minimize slippage. If the sample experiences unaccounted slippage, the apparent extension values will exceed the actual extension values.
Understanding the results and units is another area that can cause confusion. When reporting results, strength values are normalized to force per unit width of tape. Other tests for the backing materials may be appropriate for further evaluation.
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).