A lightweight, cut and puncture-resistant fabric that is used for bulletproof vests, heat-resistant uniforms or even aircraft construction. Yeah, at first glance, aramid, otherwise known by the brand name Kevlar, seems much more suitable for superhero costumes than for outdoor sports. But the properties of this very special fabric come in extremely useful in a variety of outdoor products, including gloves, trousers, helmets, backpacks and cordage. In other words, it’s definitely worth taking a closer look at aramid and how it can benefit us mountain and outdoor athletes.
What is aramid?
In a nutshell, aramid is a kind of polyamide and thus another one of the numerous hydrocarbon or petroleum-based polymers. On Wikipedia, the definition is a bit more precise, but more complex:
“Aramid fibers are a class of heat-resistant and strong synthetic fibers. […] The name is a portmanteau of ‘aromatic polyamide’. The chain molecules in the fibers are highly oriented along the fiber axis. As a result, a higher proportion of the chemical bond contributes more to fiber strength than in many other synthetic fibers. Aramides have a very high melting point (>500 °C).“
Why is it called an “aromatic polyamide”? Good question! This group of substances (at least in parts) actually releases intense (scented) aromas, which are often perceived as pleasant. As interesting as this may be, we’re much less interested in the smell than we are in the material’s functional properties.
But before we get to the most interesting and relevant ones, here is some more information on the development of the material: In the mid sixties, the American DuPont Group conducted quite a bit of research on the practical use of aramids. In the process, they developed the best-known kind of aramid Kevlar and made it ready for commercial use. Kevlar is presumably the only trade name you as an outdoor enthusiast have ever heard, seeing as this aramid fibre is often used in outdoor and mountaineering products. Actually, Kevlar is the only aramid fibre found in this area, which is why we’ll focus primarily on it and leave aramid products, like Nomex, Teijinconex, Twaron or Technora to fire fighters, soldiers and astronauts…
The production of aramids is diverse and complex, to say the least. They are produced more often as fibres than as films. In the complex world of fibre science, a distinction is made between low-modulus and high-modulus fibres, the functional properties of which differ somewhat from one another.
High modulus fibres are spun from a liquid crytalline solution of poly-paraphenylene terephtahalamide in concentrated sulphuric acid. After the surface treatment, high-modules fibres are mechanically stretched to yield a highly oriented polymer. The “high degree of orientation” makes for a clean-looking pattern. The exact geometry is just as characteristic of aramid as the golden yellow colour, which brings us to the properties of aramid.
In their own description of their Kevlar product, DuPont emphasises that these fibres are “better, stronger and safer” in the great outdoors: “DuPont™ Kevlar® aramid fiber allows people to Dare Bigger. It’s used to make a variety of clothing, accessories, and equipment safe and cut resistant. It’s lightweight, durable and extraordinarily strong. Yes, it’s best known for its use in ballistic and stab-resistant body armor, as Kevlar® brand aramid fiber continues to evolve and allow heroes to be heroes. But it’s also on the ski slopes, the switchback trails, in demanding desert terrain, even the outer limits of space.“
The wide range of applications is due to the fibre’s high (tensile) strength, high impact resistance, medium to low elongation, the good vibration-dampening properties and heat resistance. Instead of melting, the fibres begin to carbonise at about 400°C. Neither solvents, fuels, lubricants, salt water, fungi or bacteria can do much harm to aramid fibres. They are only sensitive to some strong acids and alkalis. In other words, aramid is very tough.
When it comes to compressive strength, however, aramid fabrics are more middle of the pack and fairly poor in terms of UV resistance and water absorption (up to 7%). UV radiation leads to the fibre losing up to 75% of its strength. However, this can be counteracted relatively easily by means of UV-absorbing coatings or laminates. In general, aramid can be easily combined with other fabrics, which means that its functionality can be optimised and expanded in many different ways.
The unique properties of aramid make it ideal for a wide range of applications, including construction and industry applications. The sports and outdoor industry love the material for its toughness, tensile strength and low weight. Aramid fibres are used for cords, paragliding lines, sails, bicycle tyres and more.
The Kevlar elements in textiles serve primarily as reinforcements that protect the body and increase the lifespan of garments. The Kevlar reinforcements are particularly popular in cycling, motorcycle and motorsports apparel as well as in high-wear areas of outdoor trousers and backpacks. Kevlar stitching is used in ski and via ferrata gloves as well.
Because the material is so tough, there is a certain amount of stiffness to it. This can definitely be a plus, but there are some downsides to it as well, especially in the outdoors. This is illustrated by the example of the relatively new Kevlar cords, which are also available as sewn cord slings in various sizes. The core is made of aramid, while the sheath is made of polyamide, as is the case with “normal” cords and ropes. The aramid core is brownish in colour, so it’s easy to distinguish from the conventional, dazzling white polyethylene core of your usual cord, rope and webbing material.
The 5/2014 issue of the German-language DAV Panorama magazine highlighted the high strength and high cut resistance of the material as some of the main advantages. Plus, the material is not only very abrasion and heat resistant, but it also boasts a tensile strength far greater than that of polyamide cords. Kevlar cords also offer a much higher breaking strength than conventional accessory cords with the same diameter.
As a disadvantage, Panorama magazine points to the greater amount of sheath slip shown by Kevlar cords when compared to pure polyamide. They also point out that the quasi-static material is not to be used in dynamic belays for leaders.
Because of its lack of elasticity (more precisely: low elongation to break), Kevlar is not suitable for dynamic ropes. But, the material’s stiffness really comes in useful for rock tunnels or rappelling off an Abalakov set up.
When it comes to strength, durability, longevity and safety, there’s hardly a material better than aramid/Kevlar. Its properties can be extremely useful in certain outdoor situations but less so in others. It doesn’t have as many applications in the outdoor industry as it has in cycling and motorsports, occupational health and safety and other areas, but it’s still quite useful!