To evaluate the shear strength of our adhesive tapes, we run the following test in our lab: We cut two samples with a width of 10 millimetres of the tape to be tested. They are applied onto a testliner made of recycled paper, covering a contact area of exactly 1 square centimetre each. By running a 2-kilogram metal roller over the sample four times, the tape is pressed onto the substrate, following standard protocols.

According to the Afera standard, shear strength is evaluated using a steel plate as substrate. Since in practice it is important that the adhesive bonds well with the carton fibres, we instead use testliners made from 100% recycled paper.

After the mentioned preparation, the testliner is vertically clamped into a holder in an air conditioned room at 23°C (+/- 2°C). The lower end of each sample is formed to a loop to attach a weight of 565 grams. An integrated time sensor measures the duration until the tape shears off the carton due to the permanent strain. The determined value is expressed in hours. The longer the duration, the better the shear strength. Depending on the adhesive technology used for the tape, the results vary. An outstanding performance is frequently observed with natural rubber adhesives.