What does UHMWPE stand for?
UHMWPE stands for ultra high molecular weight polyethylene. You may also hear it referred to as HMPE, or by brand names such as Spectra, Stealth Fibre.
UHMWPE is used in high-performance lines across a variety of industries, including marine, commercial fishing, mountaineering, and aquaculture. It has many qualities that make it an excellent choice for wet environments; it is light enough to float, is hydrophobic (repels water) and stays tough at low temperatures. You will also find it used in yachting, particularly with sails and rigging, as its low stretchability lets the sails maintain an optimal shape while still being exceptionally resistant to abrasion.
With its high strength to weight ratio, smooth handling and low stretch properties, it is the rope of choice for ship assist lines, offshore rigs and tankers. It is especially popular for manoeuvring vessels in distress situations.
What are the technical specifications of UHMWPE?
UHMWPE is a polyolefin fibre, consisting of extremely long chains of overlapping polyethylene, aligned in the same direction, which makes it one of the strongest rope options available.
Thanks to its molecular structure, UHMWPE is resistant to most chemicals, including detergents, mineral acids and oils. It can, however, be corroded by strong oxidising agents.
The HMPE fibres have a density of only 0.97 g cm−3 and have a coefficient of friction that is lower than nylon and acetal. Its coefficient is similar to that of polytetrafluoroethylene (Teflon or PTFE), but it has much better abrasion resistance.
The fibres that makeup Ultra High Molecular Weight Polyethylene have a melting point of between 144°C and 152°C, which is lower than many other polymer fibres, but they have no brittle point when tested at an extremely low temperature (-150°C). Most ropes will not be able to maintain their performance in temperatures below -50°C. UHMWPE rope is therefore recommended for use between -150 and +70 °C, as it will not lose any of the high molecular weight properties in this range.
UHMWPE is actually classed as a speciality engineering plastic, used for many other functions beyond rope manufacturing. In fact, medical-grade UHMWPE has been used in joint implants for many years, particularly in knee and hip replacements. This is due to its low friction, toughness, high impact strength, resistance to corrosive chemicals and excellent biocompatibility.
You may be surprised to know that UHMW plastic is also a popular choice for body armour by the military and police, again due to its high resistance and low weight.
In addition to its impressive strength qualities, UHMWPE is tasteless, non-toxic and odourless, which is why this plastic can often be used in food production plants and manufacturing. It is safe for both end-users and production workers.
