BREAKING STRENGTH 0.9 MM DYNEEMA 58 kg
A 0.9 mm thread looks like it can't handle anything. Yet this cord held up to 58 kg in the test before it broke.
This 0.9 mm Dyneema cord with a polyester sheath breaks at an average of 0.57 kN, approximately 58 kg.
Thin rope feels fragile. At 0.9 mm, it's easy to assume you could snap it with your bare hands. But this cord is made from Dyneema, the fibre with the highest strength-to-weight ratio of all rope fibres. In testing, it withstood an average of 58 kg before it fully broke. For such a thin thread, that's substantial.
The five measurements were close together. The lowest result was 0.53 kN, the highest 0.61 kN. That's a spread of just 0.08 kN. The rope therefore breaks predictably, not erratically.
0.9 mm Dyneema with polyester sheath: material and construction
This cord has a Dyneema core covered by a white polyester sheath. The core carries most of the load. The sheath protects the core against abrasion, and polyester offers excellent abrasion resistance.
This rope is part of our Dyneema cord collection. Dyneema floats on water and doesn't absorb it, so it doesn't lose strength when wet. That makes this core-and-sheath construction suitable for applications where thin, lightweight, and strong need to come together.
How we test
The cord in the testing machine, just before the core gave way first
The breaking strength tests are carried out in-house by Otto Tromm on a universal testing machine with a capacity of 50 kN. Two sets of specially developed rope clamps are available for this machine, used depending on the diameter and material of the rope.
These clamps allow rope to be tested without first splicing it.
All tests are carried out according to the guidelines of ISO 2307:2019.
This means, among other things, that each rope is tested 5 times at a test speed of 20 mm per minute. Each rope is secured so that it sits taut. No pre-tension is applied, since elongation is not measured in these tests.
For each test, 2 repetitions are filmed with a Sony camera on a tripod. The exact progression of the graph is also recorded separately on video. This allows the tension curve and breaking behaviour to be matched precisely to the graph from the breaking strength testing machine.
For each of the 5 tests, the tester also records written observations, capturing details such as the degree of elongation, the way the rope breaks, and the loudness of the snap when the rope fails.
Test results: what the testing machine showed
The cord was tested five times without a knot, at a speed of 20 mm/min. The results are close together, with a spread of just 0.08 kN between the lowest and highest measurement.
None of the five tests broke completely in one go. The core gave way first, followed by the sheath. This happened within the same continuous pull, without the test needing to be restarted for the second break. The reported breaking strength of 0.57 kN therefore applies to this phased break pattern, not to a single break through the entire cord.
How does this cord compare to other ropes
Only one measurement series is available for this cord, so a direct comparison with another product cannot be made here.
Want to know how a slightly different Dyneema cord performs? See the test of the 0.8 mm Dyneema cord with polyester sheath. It shows how diameter and construction affect breaking strength.
When to use this cord, and when not to
With a breaking strength of 58 kg, this cord is suitable for light, precision applications. It is not designed for heavy or safety-critical loads.
✓ Suitable
- Indoor window coverings — repair cord for duette, pleated, and blind systems; the white sheath is less visible against light-coloured fabric
- Pleated screen doors — anywhere 0.9 mm fits through the guides; the polyester sheath protects the core against abrasion
- Light precision lines — indoors and outdoors, up to a working load well below the measured 58 kg; Dyneema does not absorb water
✕ Not suitable
- Climbing or fall protection — the breaking strength is far too low for life-safety use
- Lifting or hoisting — 58 kg is insufficient for loads beyond human body weight
- Towing or anchor lines — too thin and too low-rated for these forces
Conclusion: thin cord, predictable strength
This 0.9 mm Dyneema cord with polyester sheath breaks at an average of 0.57 kN, around 58 kg. The five measurements were close together, so the rope behaves predictably.
Note the break pattern: the core breaks first, then the sheath, in one continuous motion. Use this cord as a repair cord for indoor window coverings and pleated screen doors, or for other light precision lines — not for lifting or safety-critical applications.
Otto Tromm pulled this cord apart five times, patiently noting each time that the core always gave way first. The sheath held on until the end, like a good understudy who never gets the leading role.