8 июля, 2015 
Malyar One major cause of adhesive tape failure is the gradual disentanglement of the adhesive polymer system under slight but prolonged shear stress. While the standard shear stress test under static load (see Section II. B) is the accepted test method to evaluate this, the nature of the results, which could be in tape movement, time to fall, or no movement whatsoever, make it difficult to compare one adhesive with another.
By converting the static shear test into a dynamic test, and running the test at a slow enough rate to allow polymer disentanglement, more meaningful and comparable data can be generated. For the butt tensile test, this rate is around 0.01 in. (0.25 mm)/min. While the width of the test sample is proportionate to the result obtained, the height of the sample on the test surface should be limited in order to limit the energy applied to the backing and so prevent adding a tensile test into the test mode. A satisfactory value is 0.25 in. (6 mm).
With increasing applied stress, the rectangular cross-section of the adhesive under stress will become increasingly trapezoidal until eventually disentanglement occurs (Fig. 11). The test is now terminated, having provided that force necessary to initiate disentanglement. The test also provides secondary information in that, if the adhesive thickness is known accurately and the distance moved before disentanglement is also known from the recorder chart, then the ratio of these two dimensions is a measure of the deformability of the adhesive, a key factor in pressure-sensitive adhesive behavior.
In conclusion, anyone testing pressure-sensitive adhesive systems should not only be fully acquainted with the fundamental characteristics of pressure-sensitive adhesives and the pitfalls in testing to ensure that the data gathered in whatever test method being used are meaningful, but the tester should also develop the skill to manipulate these test methods to meet specific needs.
|
|
Опубликовано в рубрике 