Often operating in sunny areas, ship owners have to ensure that their mooring lines won’t weaken under heavy UV exposure – but which materials are best for this? At Teijin Aramid, we conducted extensive testing to see how aramid mooring lines perform when exposed to UV light. The results are clear: braided ropes made with our aramids retain their strength very well under prolonged UV exposure. This makes them a durable, safe, and reliable solution for extremely hot and sunny climates.
The need for UV-resistant mooring lines
Vessel managers in the shipping industry often operate in sunny regions with high ultraviolet (UV) light levels. As such, they need to know that their mooring ropes will not weaken, and crewmembers will not be in danger, following long periods of UV exposure. Deterioration is not an option.
Just like other polymers, aramid fibers are sensitive to UV light. However, while a single fiber may weaken when exposed to heavy sunlight, aramid mooring lines are designed with this fact in mind. Mooring lines are made up of many fibers, which are braided together to create a thick, substantial rope.
When a single fiber of any synthetic material is exposed to UV light, it will be severely affected. However, while UV rays do partly penetrate whole mooring ropes, they only reach a depth of 0.5 filament thickness. This means only a very thin proportion of the rope’s outer layer is affected.
Testing procedure: Measuring mooring line strength under UV exposure
Mooring line UV resistance can only be accurately assessed by exposing the whole rope to scientific tests. “Our customers, including the US Navy, have used our materials all over the world for years without issues,” says Teijin Aramid’s R&D Manager. “But we knew we needed conclusive scientific evidence that would prove this to the wider industry.”
Accordingly, several R&D colleagues set out on a rigorous program to test ropes made with our aramids at the Teijin Aramid Research & Innovation Center, located in the Netherlands. To create an accurate, lifelike testing environment, the team custom-designed a UV-exposure cabinet to expose entire ropes as well as individual fibers.
The tests centered on Teijin Aramid’s three most important base yarns for mooring ropes – Twaron® 1000, Twaron® 2300, and Technora® T200 – at both fiber and rope level.
In phase one, the team measured the breaking strength of a single-yarn bundle of each of the three fibers. The bundles were put into the UV cabinet and exposed to constant UV light for 1,000 hours before being remeasured for breaking strength.
During the second phase, the entire testing process was repeated using thick braided ropes made of each fiber. In this phase, Technora® T200 was also exposed to UV light for longer than 2,000 hours, and Twaron® 2300 for longer than 4,000 hours.
Impressive test results for aramid ropes
In the single-yarn UV exposure test, individual aramid fibers lost up to 25% of their strength (see chart below), but they still retained more strength compared with other materials.
As expected, the results of the second testing phase, the braided rope test, were far more impressive. As shown by the chart above, Twaron® 2300, nor Technora® T200 lost any strength after 1,000 hours of UV exposure.
Moreover, Technora® T200 and Twaron® 2300 lost only minimal strength even after 2,000 and 4,000 hours of exposure, respectively.
In short, the tests showed conclusively that aramid-based mooring ropes perform exceptionally well when exposed to UV light, even over extended periods.
Aramid: A strong mooring rope for durability in sunny climates
Aramid’s impressive strength retention enables greater reliability and longer product lifetimes for mooring line users, particularly those operating in sunny climates. “Some of our customers have used Twaron®- and Technora®-based marine ropes for up to ten years,” says a spokesperson for the Teijin Aramid R&D Center. “This not only lowers the total cost of ownership; it also makes them a more sustainable choice.”
“Aramid’s UV-resistance can even open up possibilities for new designs that don’t require a protective cover,” he adds. “As our tests show, marine ropes made with Twaron® and Technora® retain their strength both with and without these covers. Ultimately, using aramid results in more durable ropes, guaranteeing strength – and therefore safety – for many years, whatever the climate.”
“ULTIMATELY, USING ARAMID RESULTS IN MORE DURABLE ROPES, GUARANTEEING STRENGTH – AND THEREFORE SAFETY – FOR MANY YEARS, WHATEVER THE CLIMATE.”