Accuracy of test methods
Joint statement of Afera and IVK, the German Adhesives Association, on specification limits for adhesive tapes
It is state of the art that for the approved adhesive tape characteristics (e.g. “adhesive bond strength”), no discrete measured values can be determined as the measuring methods themselves will not deliver discrete values.
Based on the product specifications agreed between manufacturer and customer, measurement systems in the adhesive tape industry cannot always fulfil the requirement of relevant QM systems of R&R ≤ 10 % or 10 to 30 % of tolerance, even though they are “state of the art”. The majority of test methods for adhesive products consists of destructive tests. Therefore, the measurement system variation, according to Measurement System Analysis, contains a significant portion from inherent differences between the samples. An instructive paper regarding the precision of the peel adhesion test – one of the most important tests in the tape industry – has been provided by Richardson et al. [1]
It is the collective view of industry experts that no better test methods are currently available. Afera and IVK recommend that member companies consider these findings when evaluating their measurement systems.
For the characteristics of adhesive tapes (peel strength, unwind force, shear strength, thickness, etc.) tested in accordance with the recognised international standards, apply therefore only confirmed specification limits. In some cases, it might be sufficient to state just the value of the lower or upper specification limits which then shall not be undershot or exceeded.
The characteristic values obtained through standards, such as peel strength, unwind force and shear strength, always relate to the surfaces and conditions mentioned in the standards. Therefore, when selecting an adhesive tape for a specific application, the user must consider the actual requirements which are necessary for this application and not covered by the respective standard. 2
When it comes to using tapes for specific applications, IVK and Afera advise that the user validates the products in the event of a deviation from the standard conditions, ensuring that the specified, bonding-relevant process parameters (like condition, shape, type and surface quality, temperature, moisture and pressure) are followed. This is essential as the tape manufacturer, when functioning as the supplier, has no influence on the user's process design. "Best Practice" can be found in railway vehicle construction, for which validation through the user has been regulated by the standard DIN 6701 (converted to EN 17460 from September 2022 on), which the Eisenbahnbundesamt (Federal Railway Authority) declared as the state of the art for this industry in 2007.
¹ P. Richardson and H. P Acton, “Work on Afera 4001 and its Impact on Business,” a paper presented at the 19th PSTC Technical Seminar in 1996.
² refer to EN 60454-3-1:1998, 1.1 Scope