A datasheet that says “strong” tells you nothing. A datasheet that says 3.2 N/25 mm tells you something — if you know which direction that force is applied in.
Peel strength
Peel is measured by bonding two 25 mm wide strips, then pulling one away from the other at roughly 90 degrees, at a fixed rate, on a tensile tester. The result is the average force over the pull, expressed in newtons per 25 mm.
Peel is what resists opening a joint like a book. It is the number buyers ask for, and the least useful one on its own, because almost no real load is applied as a clean 90-degree peel.
Shear strength
Shear is measured by loading the closed joint along its own plane — pushing the two halves sideways — and recording the force at which they slide. It is reported in N/cm².
Shear is what holds a cable bundle, a seat cushion under a body, or a panel against gravity. A tape with 3.2 N/25 mm peel and 12 N/cm² shear will carry a surprising amount of weight in shear and almost none in peel. Specify by load direction, not by the biggest number.
Typical values by construction
| Construction | Peel (N/25 mm) | Shear (N/cm²) | Cycles |
|---|---|---|---|
| Ultra-thin 0.8 mm | 2.4 | 8 | 3,000 |
| Standard nylon | 3.2 | 12 | 5,000 |
| Heavy-duty nylon | 6.0 | 22 | 10,000 |
| Injection-molded hook | 4.5 | 16 | 20,000 |
| Back-to-back | 3.0 | 11 | 5,000 |
Why narrower tape underperforms
Peel per 25 mm stays roughly constant as width changes, but real-world holding force does not scale linearly, because narrower tape engages fewer hooks at the edge, and the edge is where peeling starts. A 10 mm strip of the same construction measures lower than a 50 mm strip in practice. Our catalogue applies a width factor of 0.85 to 1.00 for this reason.
Cycle life
Cycle life is the number of open-close cycles before peel falls below 80% of its initial value. It is measured by machine, not by hand, at a fixed rate and engagement pressure.
Two things shorten it dramatically: contamination (dust, fibres, sand in the hook) and closing misalignment. A joint that is closed at an angle wears the hook tips on one side only. If your assembly is done by hand at speed, design for 30–40% of the rated cycle life and you will not be disappointed.
Setting a safety factor
For static loads in shear, a factor of 3 over the measured value is reasonable. For peel, use 5. For anything that vibrates, add 50% on top. For anything safety-relevant — a helmet liner, a fall-arrest component, a medical device — hook and loop should not be the only load path, regardless of the number.
How to test your own part
Clamp the assembled joint in a vice with the load direction matching real use, hang weights until it slips, then divide by 3. Repeat after 200 cycles. If the second number is more than 20% lower, the construction is wrong for that duty cycle — not the tape.
Need this applied to your part?
Send the substrate, the load and the drawing. We will come back with a construction, a tolerance and a sample date.
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