UHMWPE (Ultra high molecular weight polyethylene uhmwpe) ropes are used as high performance lines across multiple industries including marine and industrial, commercial fishing, mountaineering and mountain climbing, yachting and aquaculture.
You'll notice that a lot of the industries mentioned above are marine based. It has qualities that make it an excellent choice for wet environments; it's light enough to float and is hydrophobic.
In combination with its excellent strength to weight ratio, low stretch and easy handling, it's the rope of choice for ship assist lines, safety lines, offshore rigs and tankers (this rope is included in the OCIMF's Guide to Purchasing High Modulus Synthetic Fibre Mooring Lines.
What is UHMWPE?
UHMWPE is a polyolefin resin of a very high molecular mass (between 2 and 6 million g/mol). It is formed of extremely long chains that are produced by wet or dry gel spinning. The long chain transfers load more efficiently onto the polymer backbone by strengthening intermolecular interactions. The product of this is an extremely tough material with the highest impact strength of any thermoplastic currently in production.
UHMWPE is tasteless, odourless and non-toxic. With the exception of oxidising acids, it's also highly resistant to chemical corrosion. If you'd like to delve deeper into the science of UHMWPE then head over to it's Wiki page.
Wire Rope Replacement
UHMWPE is at least 15 times stronger than steel or wire rope equivalents. They're multiple times stronger than polyester lines of comparable weight. In addition to their strength, they're also much safer than wire. The recoil force is much less than steel rope on failure. On breakage, steel wire rope has a very unpredictable recoil and displays uneven breakage behaviour. This is due to the way that wire rope is coiled. When it's made, multiple strands of metal wire are twisted into a helix to form a composite rope. When the rope breaks, the helical rope unravels rapidly, causing razor-sharp edges to release with dangerous force.
When these ropes break, the recoil force is significantly less. This is down to the fact that it's made up of long chains of overlapping polyethene, orientated in the same direction. This overlapping increases the bond strength. On breakage, it displays a linear, predictable recoil.
These ropes are increasingly replacing steel and conventional wire ropes in lifting, shipping and offshore applications. Recently some shipping companies have even begun to use them in cranes.
Switching over to a UHMWPE line can help to reduce risk factors on work sites.
UHMWPE cord is designed to overcome four key challenges common in mooring, towing, as a winch rope and heavy duty lifting. These are abrasion resistance, bending-fatigue, compression and creep-fatigue.
1. Abrasion resistance
The ropes abrasion lifetime that is up to 4 times greater than steel wire rope and rope made from regular HMPE and polyester. It's an excellent investment that will last a long time. In mooring, arborist, and lifting operations, the rope will often be in contact with an uneven, rough surface. Over time, this can wear away at the fibres, impacting their quality, performance and safety.
2. Bending fatigue and compression
Bending fatigue occurs whenever a rope flexes or bends under tension. This can wear out the rope and reduce its lifetime. Compression fatigue occurs when the rope is compressed. Both of these need to be taken into consideration when using rope in high-load situations.
As previously mentioned, it's made up of long chains of overlapping polyethene fibres. This means that compression and bending fatigue are considerably less than in synthetic and steel equivalents.
Creep-fatigue happens when a rope elongates in high temperatures. Over time, it can lead to catastrophic failure of the rope and is a major risk factor in ropes made from normal synthetic fibres or regular HMPE. UHMWPE, on the other hand, has a creep lifetime up to 4 times greater than generic HMPE.
Wire rope can be cumbersome to handle and requires significant logistical operations to transport it. UHMWPE line is 1/8th of the weight of steel wire rope and 8 times stronger. This makes it an excellent wire rope replacement.
UHMWPE as a Dyneema Equivalent
Our high performance UHMWPE is essentially the same as Dyneema Rope without the brand name. It's chemically identical but with a slightly different braid that has no impact on the properties of the line.
Benefits of this rope
- Absorbs hardly any water
- High performance
- High melting point
- High strength
- Low density - it floats on sea water
- Low weight
- Safer than wire - breaks in a linear fashion
- UV resistance - prolonging lifetime of your rope
- Low maintenance
- Superior abrasion resistance to Teflon and other synthetic lines
- Ultra-low stretch (3–4% at breaking load)
- Reduced cost
- Chemical resistant
- Low dielectric constant - it's almost transparent to radar