Aramid (PPTA) — does not melt, barely stretches, stronger than steel
6 products · own tensile tester data 2026
Discover our full collection of Kevlar cord below — available by the metre and direct from stock. Scroll down for our measurement data, technical specifications, applications and frequently asked questions.
Own measurement data
Breaking strength of Kevlar cord: our own tensile tester data (2026)
All values below were measured in our own laboratory according to ISO 2307:2019, with 5 pull tests per cord, without knot, carried out by technical director Otto Tromm. The breaking strength is the average of those five pulls.
Measured breaking strengths Kevlar cord — own tensile tester, avg. 5 pull tests, without knot (ISO 2307:2019)
| Variant | Diameter | Construction | Breaking strength (avg.) | Spread 5 pulls | Break pattern |
|---|---|---|---|---|---|
| Pure Kevlar (no sheath) | 3 mm | 8-strand braided, no core | 596 kg (5.85 kN) | 4.3% | 1 phase, falls apart |
| Kevlar + polyester sheath (black) | 4 mm | core-sheath, 3 twisted strands | 302 kg (2.96 kN) | 5.1% | 2 phases |
| Kevlar + polyester sheath (black) | 3 mm | core-sheath, 2 braided cores | 220 kg (2.16 kN) | 13.4% | 2 phases |
| Kevlar + neon yellow sheath | 3 mm | core-sheath, twisted core | 162 kg (1.59 kN) | 5.0% | 2 phases |
| Kevlar + polyester sheath (black) | 2 mm | core-sheath, 3 twisted strands | 117 kg (1.15 kN) | 6.1% | 2 phases |
| Kevlar + polyester sheath (black) | 1.5 mm | core-sheath, coated braided core | 107 kg (1.05 kN) | 11.4% | 2 phases |
This is not a manufacturer's specification and not an estimate — these are our own measured values.
Construction vs fibre
Does construction or fibre determine the breaking strength of Kevlar cord?
Construction. Compare the three 3 mm variants: exactly the same fibre (Kevlar), exactly the same diameter (3 mm), but three completely different outcomes.
The pure cord is 2.7× stronger than the core-sheath version and 3.7× stronger than the twisted variant. The reason is measurable: with pure Kevlar 100% of the cross-section carries load, while with a core-sheath part of the cross-section consists of non-load-bearing polyester and the core contains less Kevlar. Per millimetre of diameter, pure Kevlar delivers approx. 199 kg/mm, compared with 59–76 kg/mm for the sheathed variants.
Conclusion for the buyer: when buying Kevlar cord, never ask only about the diameter, but always about the construction. Diameter alone does not predict strength.
Core construction
Twisted core vs braided core in Kevlar cord: 26% difference
Two of our 3 mm variants differ only in the construction of the core.
| Core construction | Breaking strength (3 mm) |
|---|---|
| Braided cores (twisted strands) | 220 kg |
| Twisted core (loose parallel fibres) | 162 kg |
The twisted core is 26% weaker (58 kg less) at the same diameter and fibre. With loose parallel fibres the load is distributed unevenly: fibres fail one by one instead of together. Braided or twisted cores distribute the load better and achieve a higher breaking strength. Anyone looking for maximum strength per millimetre should avoid the twisted construction.
Residual strength & break behaviour
How does Kevlar cord break? Residual strength and break behaviour from our tests
One property that matters for safety and that you will not see measured anywhere else: our core-sheath variants do not fail suddenly, but in two phases. After the first (often invisible) break the cord still retains a large part of its strength.
Residual strength after the first break — own pull tests
| Variant | Residual strength after 1st break |
|---|---|
| 2 mm core-sheath | ±93% |
| 3 mm core-sheath (black) | ±78% |
| 1.5 mm core-sheath | ±77% |
With the 1.5 mm we saw the second break returning remarkably reproducibly.
4 out of 5 times exactly at 0.82 kNPure braided Kevlar behaves differently: it breaks completely in one go and then comes apart — logical, because without sheath and core there is no second load-bearing layer.
With our 4 mm the first break was lower than the next — the opposite of the normal pattern. We would rather report that than omit it; it is exactly the kind of deviation that occurs in a real test series.
Efficiency per mm
1.5 mm vs 2 mm Kevlar cord: why only 10 kg difference
Between our 1.5 mm (107 kg) and 2 mm (117 mm) there is only 10 kg difference — while the 1.5 mm has a 33% smaller diameter. Per millimetre of diameter, the 1.5 mm is therefore clearly more efficient (71 kg/mm versus 59 kg/mm for the 2 mm). For applications where diameter and weight count, the 1.5 mm delivers relatively a lot of breaking strength. This is due to the ratio between Kevlar core and polyester sheath in both cords.
Material comparison
Kevlar cord vs Dyneema vs polyester (our measured figures)
Many people think Kevlar is the strongest rope. In our tensile tester that is not the case: in breaking strength per diameter, Dyneema wins. Our measured values at equal diameter:
| Diameter | Kevlar (core-sheath) | Dyneema (braided) |
|---|---|---|
| 1.5 mm | 107 kg | 256 kg (2.4× stronger) |
| 2 mm | 117 kg | 203 kg (1.7× stronger) |
So Kevlar does not distinguish itself on raw pulling force, but on heat and dimensional stability. The full property comparison:
| Property | Kevlar (aramid) | Dyneema | Polyester |
|---|---|---|---|
| Specific gravity | 1.44 g/cm³ (sinks) | 0.97 g/cm³ (floats) | 1.38 g/cm³ (sinks) |
| Breaking strength per diameter | high | highest | average |
| Elongation at break | 2.5–3.5% | 3–4% | 12–15% |
| Heat resistance | ★★★★★ (does not melt) | ★★☆☆☆ (melts ±144°C) | ★★★★☆ (melts ±250°C) |
| Creep | ★★★★★ (< 0.03%) | ★★☆☆☆ (creeps under load) | ★★★★☆ |
| UV resistance | ★★☆☆☆ (sheath required) | ★★★★☆ | ★★★★☆ |
| Cut resistance | ★★★★★ | ★★★★☆ | ★★★☆☆ |
| Price | €€€ | €€ | € |
| Best for | heat, dimensional stability, minimal stretch | strength/weight, floating | UV, shock, budget |
Conclusion: choose Kevlar cord for heat (does not melt, stable up to approx. 160°C) and dimensional stability under long-term load (virtually no creep). For maximum strength per millimetre or a floating rope, Dyneema is the better choice. For budget and UV exposure, look at polyester.
Technical information
Technical specifications of Kevlar cord
Specifications
| Material | Aramid (PPTA), brand name Kevlar® |
| Specific gravity | 1.44 g/cm³ (sinks) |
| Elongation at break | 2.5–3.5% |
| Melting point | none — chars at approx. 425–480°C |
| Working temperature | –46°C to +160°C (up to 149–177°C for longer periods) |
| Cold behaviour | no embrittlement down to –196°C |
| Creep | < 0.03% |
| Moisture absorption | approx. 4.5–5% |
| UV resistance | low (sheath protects the core) |
| Cut resistance | high |
Important when using
Important with Kevlar cord: the fibre tolerates sharp bends and knots poorly. For a permanent loop we therefore recommend a splice over a knot. With a cord with polyester sheath, the sheath (melts approx. 250°C) sets the upper limit — not the Kevlar core itself. Avoid direct, prolonged exposure of pure (unsheathed) Kevlar to sunlight and strong acids.
Diameters & measured breaking strength
Types and diameters of Kevlar cord at Prorope
Kevlar cord with black polyester sheath (core-sheath) — measured breaking strength per diameter
| Diameter | Breaking strength (own test) |
|---|---|
| 1.5 mm | 107 kg |
| 2 mm | 117 kg |
| 3 mm | 220 kg |
| 4 mm | 302 kg |
BestsellerOur bestselling line. The sheath protects the UV-sensitive core from sunlight and wear. Available in 1.5 · 2 · 3 · 4 mm — see the table above (107–302 kg).
View cord
Neon yellow · 3 mmSame Kevlar, eye-catching colour, twisted core: 162 kg in our test.
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Highest strength8-strand braided, highest strength per diameter (3 mm = 596 kg), but UV-sensitive and frays at break.
View cordBuy Kevlar cord at Prorope
Buy Kevlar cord at Prorope
Prorope supplies Kevlar cord directly from our own stock. All cords are available by the metre and are shipped the same day when ordered before 1:00 PM. We supply private customers, machine builders, industry and the model building and kite sports sectors.
Unsure about the right diameter, variant or finish? Our rope specialists are happy to calculate with you.
Need personal advice?
Our rope specialists are happy to help you with the right diameter, variant or finish for your application.
+31-77 208 6139 · info@prorope.com
Frequently asked questions