Nylon is known as the rope for shock absorption — but how strong is a braided nylon rope of 6 mm in an actual tensile test? The sheath-core construction of this rope, with two parallel cores, differs from most standard 6 mm ropes. That makes it worth measuring.
What is the breaking strength of braided nylon 6 mm? In our test, this rope broke at an average of 6.75 kN (688 kg).
That is notably high for a 6 mm rope — the average at this diameter is around 3.90 kN.
Braided nylon 6 mm (sheath-core, two parallel cores) broke at an average of 6.75 kN (688 kg) in our test.
That is 73% stronger than the average for 6 mm ropes. The spread between measurements was large: from 6.34 kN to 7.10 kN.
Suitable for shock loading; less suitable for static or precision applications where a tight load curve is required.
What type of rope is this?
This is a braided nylon rope with a sheath-core construction. The core consists of two parallel strands; the sheath surrounds the core and provides protection against wear. The material is nylon — also known as polyamide (PA).
Nylon has the highest elongation of all synthetic fibres: 20–35% at break. That makes it suitable for applications where shock absorption is important, such as anchor line work, towing and pulling.
The parallel core construction contributes to a higher fill mass per millimetre of diameter, which explains the notably high breaking strength compared to other 6 mm ropes.
Nylon absorbs water and consequently loses 10–15% of its breaking strength when wet. This must be accounted for in safety calculations for wet applications.
Test methodology
The tests were carried out on a universal testing machine with rope-specific clamps, suitable for measuring rope without splicing.
The test speed was 20 mm/s. A total of 5 repetitions were performed.
No pre-tension was applied prior to the tests.
The measured values are the actual breaking loads as recorded by the machine.
Test results
The average breaking strength across 5 tests is 6.75 kN (688 kg). The highest measured value was 7.10 kN; the lowest was 6.34 kN.
The spread of 0.76 kN between the lowest and highest measurement is relatively large for a rope of this size. This is a relevant factor when determining a safe WLL (working load limit). For safety applications, calculations are typically based on the lowest measured value, not the average.
Notable in the load curve: the rope did not break along a tight, smooth line. The curve rose in a stepped, irregular manner — with clear interruptions in the build-up of tensile force.
This indicates sequential failure of individual fibres or strands, rather than simultaneous failure of the entire cross-section.
Just before breaking, an audible ticking sound was present. In practice this may serve as an early warning signal, but it should not be treated as a reliable indicator of imminent failure.
Comparison with other 6 mm ropes
The average breaking strength of 6.75 kN places this nylon rope at the top of the 6 mm category tested. For comparison:
- polypropylene 3-strand twisted: 6.58 kN
-
ppmf: 5.30 kN
The braided nylon rope is therefore 73% stronger than the average of 3.90 kN for 6 mm ropes, and also exceeds the polypropylene rope of the same diameter by 0.17 kN.
The sheath-core construction with two parallel cores plays a clear role in this.
When is this rope most suitable?
This rope is best suited for applications where shock absorption and higher breaking strength per millimetre of diameter need to be combined. Specifically:
- Anchor line work: the high elongation (20–35%) absorbs shocks from wave motion or wind gusts, reducing peak loads on attachment points.
- Towing and pulling: the rope takes up dynamic loads without failing immediately.
- Lashing and securing (light class): with a WLL calculated using a safety factor of 5:1 based on the lowest measured value (6.34 kN), this gives a WLL of approximately 1.27 kN (129 kg).
- Applications where a warning signal before failure is desirable: the ticking sound and stepped load curve may provide early warning of failure in some situations.
Limitations
This rope is not suitable for the following applications:
- Static high-load applications with minimal elongation: nylon elongates 20–35% at break. In applications where minimal elongation is required (lifting, rigging, survey line work), this material is unsuitable.
- Wet safety calculations: nylon loses 10–15% of its breaking strength when wet. The measured dry value of 6.75 kN drops to approximately 5.74–6.08 kN. Safety margins must be adjusted accordingly.
- Applications requiring a tight, predictable load curve: the stepped curve and large spread (6.34–7.10 kN) make this rope less suitable for precision applications or certified lifting work.
- Prolonged UV exposure without protection: nylon degrades faster under UV than polyester, though more slowly than polypropylene.
- Prolonged static load at high temperature: not applicable to nylon to the same degree as HMPE, but prolonged thermal exposure above 80°C affects strength.
Alternatives
For applications requiring lower elongation and greater dimensional stability at a comparable diameter, consider:
- Braided polyester 6 mm white per metre — polyester elongates only 10–15% at break, loses less than 5% of its strength when wet, and has excellent UV resistance. Suitable for rigging and marine applications where low elongation is a priority.
- Prorope HMPE rope (6 mm, price per metre, Blue) — HMPE has an elongation of less than 4% at break and a breaking strength 2–5× higher than polyester of the same diameter. No water absorption. Suitable for high-load static applications where weight and elongation are critical.
Conclusion
Braided nylon 6 mm with sheath-core construction delivers a notably high breaking strength of 6.75 kN (688 kg) on average — almost double the average for 6 mm ropes. The rope is best suited for dynamic applications such as anchor line work and towing, where shock absorption and higher breaking strength per millimetre of diameter need to be combined. The large spread in the test results (6.34–7.10 kN) and the stepped load curve make this rope less suitable for certified lifting work or applications that require predictable and uniform failure behaviour.
This test was carried out by Otto Tromm, who now firmly believes that a 6 mm nylon rope with two parallel cores is stronger than his morning coffee — and that says something, because that also starts in a stepped, irregular fashion.
The test data were collected by Prorope. This text was generated using AI on the basis of those data and verified for factual accuracy. Read how we test and publish →