Plastic, please – when life hangs on a thread

People climb and scale the steepest mountain walls and swing themselves up to dizzying heights, usually trusting that a plastic product will save their lives in the event of a fall. This polymer saviour celebrates its birthday: On 16 February 1937, the US chemical company Du Pont applied for a patent for the versatile and resilient synthetic fibre "nylon".

Even a toddler balances light-footedly and safely on a high wall when his hand is guided by that of an adult. Without the supporting handhold, many a walk on a narrow ridge would be on wobbly legs and probably end in a fall, because unrestrained gazing into steeply sloping depths can cause dizziness and loss of balance. Experts in mastering great heights, when travelling in groups, also rely on contact, not by grasping the hands. When hiking and climbing in steep and insecure terrain, a rope generates a grip-like feeling of safety. It ties the participants of a mountain hike or climbing tour into a "rope team" or gives them a secure hold on a steel pick sunk into a rock face.

Until the 1960s, hemp ropes were common and widespread as a binding element in alpine environments. The natural fibre, beaten into ropes as thick as a finger, performed its service even under the greatest strain, until rain and dirt caused the fibres to wear out. A process that takes place in secret and is rarely obvious: even if the hemp rope appears dry on the outside, no one knows exactly what it looks like in its inner core. Often enough, the weakness of the material only becomes apparent when the rope is put to the test and comes under great tensile forces, such as those that occur when a body falls from a great height. Until the 1960s, when an alpinist had a fatal accident in the mountains, it was often due to a broken rope. Even the thickest hemp ropes gave way when the fibres were rotten.

At the end of the 1950s, an invention by the US chemical company E. I. du Pont de Nemours and Company, better known by its abbreviated name DuPont (after the merger with Dow Chemical, it initially traded under the name DowDuPont and since June 2019 under DuPont de Nemours) and its employee Wallace Hume Carothers (1886-1937), brought about a lasting improvement in the safety of high-alpine mountain sports. The substance we are talking about is called polyhexamethylene adipic acid amide in the language of chemists. Plastics experts like to use the abbreviated form polyamide. For laymen, on the other hand, it is better known as nylon (or perlon): what was woven at the time, i.e. in the middle of the 20th century, as a low-cost silk substitute for ladies' pantyhose or tear-proof cloth for parachutes, could later be woven into highly resilient, stable rope material. DuPont applied for a patent for nylon in the USA on 16 February 1937.

Processed into women's stockings, nylon made a public career worldwide. However, the first completely synthetically produced synthetic fibre was first used in the general public, namely as toothbrush bristles [2]. With the entry of the USA into the Second World War, however, the importance of nylon also increased as a material important for defence. The military recognised the benefits of this extremely light but highly robust synthetic fibre and used it to manufacture parachutes, tents or camouflage nets. However, it was not only the military who were convinced by the property profile of polyamide: what had proven itself in security-relevant areas during the war quickly found use under civilian conditions as well.

It was therefore only a matter of time before nylon fibres were also used in the world of high alpine sports and high-altitude rescue. Since their introduction, i.e. that of climbing and mountaineering ropes made of nylon fibres, the number of fatal falls in the mountains due to rope breaks has decreased significantly. Nevertheless, it sounds almost paradoxical, "if climbers are connected by a rope, the risk of falling can increase drastically", Holger Kreitling quotes a training manager at the German Alpine Association in his Welt article "Die falsche Sicherheit der Seilschaft" [3]. However, the author provides an important argument for this thesis: without fixed points that can actually withstand the load, the rope "conveys a false sense of security", Kreitling writes. It is not only the material and its property profile and quality that matter, but also, in a very special way, the person and his or her specific skills and experience in handling and dealing with the material [4].