Standard Test Methods for Loop Tack
ASTM D6195 specifies a few procedures to measure quick stick adhesive strength. This test is different from a peel test because the tape is not given enough time or pressure to fully adhere to the test plate. This type of test is often used by label manufacturers to test the adhesion quality of their labels in an automated packaging line.
The Tag and Label Manufacturers Insitutue (TLMI) greatly influences this test and also specifies another quick peel strength test where the tape is peeled at 300mm/min. TLMI also manufactures tape and label testing equipment, however all of these types of tests can also be performed on a universal testing machine.
A loop of standard length and width is positioned in such a way that the adhesive is on the outside of the loop. The two ends of the loop are secured by vise grips. During the test, the loop is lowered onto the loop tack test fixture which has a 1x1 inch substrate platform.
The loop tack test fixture is a raised metal platform made of stainless steel. The tape loop must come down onto the platform and cover it so that the edges of the loop slightly overhang the end of the platform. the loop tack base is usually used in combination with vise grips.
Loop tack is measured by the peak load exhibited during the test. It is typical for a handfull of similar samples to be tested in a lot or a batch and averaged together. Adhesives will perform differently based on the flexibility of the label or backing material in use because it changes the angle of the peel.