The properties and performance characteristics of any rope are reliant on the materials from which they are made.
The following series of tables sets out to compare the key physical properties of the most frequently used materials.
MODULUS, STRENGTH AND ELONGATION
Modulus, strength and elongation are all interconnected
| MATERIAL | MODULUS Tenacity (g/Denier) | STRENGTH Tenacity (g/Denier) | ELONGATION (% at break) |
|---|---|---|---|
| Dyneema SK99 (HMPE) | 1800 | 48 | 3.6 |
| Dyneema SK78 (HMPE) | 1267 | 40 | 3.5 |
| Dyneema DM20 (HMPE) | 1042 | 35 | 3.6 |
| Zylon Type HM (PBO) | 1948 | 42 | 2.5 |
| Zylon Type AS (PBO) | 1302 | 42 | 3.5 |
| Zyex (PEEK) | – | 6.5 | 30 |
| Teflon (PTFE) | 13 | 2 | 8.5 |
| Technora (Para-Aramid) | 590 | 27 | 4.5 |
| Twaron (Para-Aramid) | 600 | 23 | 3.6 |
| Vectran (LCP) | 600 | 25.9 | 3.8 |
SPECIFIC GRAVITY
Specific gravity (buoyancy of a rope/material) Specific gravity is a measure of the density of a material; a Specific Gravity of 1.0 is equivalent to a density of 1g per cm3 (i.e. a Specific Gravity <1 means the material floats). The following table shows the specific gravity of some of the materials commonly used in fibre ropes.
| MATERIAL | SPECIFIC GRAVITY |
|---|---|
| Polypropylene | 0.91 |
| HMPE (Dyneema) | 0.98 |
| Fresh Water | 1 |
| Salt Water | 1.03 |
| Nylon | 1.14 |
| Polyester | 1.38 |
| Vectran | 1.41 |
| Aramids (Technora, Twaron, Kevlar, Nomex) | 1.44 |
| Zylon | 1.54 |
| Steel | 7.85 |
ULTRA-VIOLET RADIATION RESISTANCE
All materials are affected by UV radiation to some extent. The actual affect on a rope by UV is very difficult to predict as it is reliant on a number of random factors such as intensity of UV and length of exposure.
The table on the right attempts simply to rank different materials in line with their resistance to UV radiation on a scale of 1 to 5, with 5 being most resistant to UV and 1 being least resistant.
Please refer to the Rope Care Advice section for more information.
| MATERIAL | UV RANKING |
|---|---|
| Polyester | 5 |
| HMPE (Dyneema) | 5 |
| Nylon (UV treated) | 4 |
| Aramids (Technora, Twaron, Kevlar, Nomex) | 3 |
| Vectran | 3 |
| Polypropylene | 2 |
| Zylon | 1 |
MELTING POINT
The table on the left shows the typical melting or decomposition temperature of some common rope making materials.
Please refer to the Rope Care Advice section for more information.
| MATERIAL | MELTING POINT (DEG. C) |
|---|---|
| Zylon | 650 (Decomposition) |
| Aramids (Technora, Twaron, Kevlar, Nomex) | 500 (Decomposition) |
| Vectran | – |
| Polyester | – |
| Nylon (6.6 / 6) | 250 / 220 |
| Polypropylene | 170 |
| HMPE (Dyneema) | 150 |
CHEMICAL RESISTANCE
Exposure to chemicals can have a significant affect on the strength and performance of ropes, depending on the material used in construction. This table details the residual strength of synthetic fibres after chemical exposure under specific conditions.
Nylon ropes are particularly badly affected by exposure to most acids. For this reason, Marlow developed a special Halochromic indicating (acid indicating) marker incorporated into to some of our nylon PPE Static Ropes.
| TEST CONDITIONS | RESIDUAL STRENGTH | |||||||
|---|---|---|---|---|---|---|---|---|
| Chemical | Concentration Chemical / water % | Temperature Deg. Centigrade | Exposure Hours | Nylon | Polyester | Polypropylene | Aramid | HMPE |
| Acids | ||||||||
| Hydrochloric | 34% | 20 | 100 | 0% | 90% | 100% | 95% | 100% |
| Nitric | 66% | 20 | 100 | 0% | 70% | 100% | 95% | 95% |
| Formic | 90% | 20 | 100 | 0% | 95% | 100% | 90% | 100% |
| Acetic | 100% | 20 | 100 | 85% | 95% | 100% | 100% | 100% |
| Alkalis | ||||||||
| Caustic soda | 40% | 20 | 100 | 50% | 0% | 90% | 90% | 100% |
| Caustic soda | 20% | 70 | 150 | 100% | 0% | 100% | 85% | 90% |
| Caustic potash | 20% | 20 | 100 | 90% | 0% | 90% | 90% | 100% |
| Solvents | ||||||||
| Trichloroethylene | 100% | 30 | 150 | 100% | 95% | 80% | 100% | 100% |
| Carbon tetrachloride | 100% | 20 | 150 | 100% | 100% | 100% | 98% | 100% |
| Benzene | 100% | 70 | 150 | 100% | 100% | 100% | 98% | 95% |
| Metacresol | 100% | 100 | 4 | 0% | 0% | 100% | 80% | 100% |
| Oxidising agents | ||||||||
| Hydrogen peroxide | 10% | 20 | 100 | 0% | 100% | 90% | 95% | 100% |
