Jogging shoes and co.: plastics in sportswear
31.07.2024
The right outfit for every sport - what was long the preserve of competitive athletes has now become an integral part of leisure sports. Even for a short jog after work, sports enthusiasts can access sophisticated equipment. From breathable sports shirts, cooling or warming (depending on the season) running tights or running shoes with a medium or high drop, for overpronation or not. The choice is varied and sometimes difficult. However, there is one unifying factor that most models have in common, whether shoe or cap, trousers or jacket - plastics are used in their manufacture.
The use of plastic in sportswear is due to its diverse properties, which make production easy and enable the desired results to be achieved. Jogging shoes/running shoes, for example, can be made particularly light and flexible by using plastic foams (often EVA or TPU) in the soles. When running, they can absorb the impact forces well thanks to a good midsole to relieve the heel and knees or also return the energy to the runners, which is particularly desirable in competitive sports, for example. (Although not always permitted, see box below). The synthetic outsole in turn ensures that the shoe is waterproof and durable. The upper itself can be customised to meet specific requirements by using different materials: breathable, waterproof, warming or cooling. In addition to synthetic materials, wool is also used here.
A few years ago, the Nike Vaporfly made a name for itself in competitive sports (see Ineos 1:59 Challenge). In 2019, runner Eliud Kipchoge became the first person to run a marathon in just under two hours (not an official world record as it was a test run!). He had his shoes to thank for this, among other things. The Nike Vaporfly were characterised by a particularly thick, 40-millimetre sole. A carbon fibre plate improved the runner's energy efficiency by making it easier to push off from the ground and promoting forward movement. In addition, Nike used a special ZoomX foam in the midsole, which provided exceptional cushioning and energy return, reducing fatigue and increasing running performance. The advantages over other shoes were so immense that the competition shoe in this form was banned by the World Athletics Association in 2020. It is also no longer permitted to wear test shoes, only models that have been on the market for four months.
In sports shoes in particular, consumers cannot always know exactly which plastics are used, as manufacturers sometimes give their own names to their plastic soles etc. Company secrets and patents developed for production play a role here.
However, general information on the materials used does exist. It is clear that modern jogging shoes use materials such as ethylene vinyl acetate (EVA) and thermoplastic elastomers (TPE).
Thermoplastic polyurethane (TPU) is another popular material that is valued for its high flexibility and durability. TPU is often used in midsoles and outsoles to improve both the durability and performance of footwear. It enables optimal energy return, which can contribute to a more efficient running style.
3D printing is also increasingly being used in the manufacture of sports equipment. Professionals are usually the driving force here, as adjustments to weight and structure - be it the running shoe or the precisely fitting shin guard - can ensure better performance.
The company On from Switzerland has presented a completely new application for the upper material of running shoes just in time for the 2024 Olympic Games. A running shoe that is sprayed! The Cloudboom Strike LS has been under development since 2018 and Kenyan runner Hellen Obiri won the Boston Marathon in a development version in 2020. However, she is likely to attract a lot of attention when she competes in this model at the 2024 Olympic Games in Paris in August. Made from just seven parts, the midsole, which consists of a special Pebax mixture called Helion™ HF hypofoam, is sprayed onto a blank foot in three minutes using the so-called LightSpray™ method, without the use of adhesives and like a spider's web. The shoe is then put on like a sock and should fit the foot perfectly. Weighing between around 160/170 grams (depending on shoe size), the shoe is a real lightweight.
If you happen to be in Paris: On will be showing a live production of the Cloudboom Strike LS at the ‘On Labs Paris Pop-up’ at 27 Boulevard Jules Ferry in Paris for the Olympic Games in Paris until 10 August.
To improve their environmental footprint, more and more manufacturers are turning to recycled plastics made from recycled PET bottles or other plastic waste. Recycled polyester is familiar from fleece jackets, for example, but is also used for sports T-shirts or sports trousers. Modern recycling technologies now make it possible to produce high-quality plastics that offer the same performance and durability as new materials. Together with more sustainable production methods, the ecological footprint can be improved. Unfortunately, it is not yet possible to produce a complete closed-loop system. Depending on the production process, it may not be possible to separate the plastics - for example in an upper - by type.
Bio-based plastics, which are made from renewable raw materials such as maize, potatoes or sugar cane, are also becoming increasingly important in sportswear production. Modern manufacturing processes make it possible to produce bio-based plastics with outstanding technical properties and are therefore being used more and more.
All in all, there are some very exciting developments in the field of sporting goods and their manufacturers, which are likely to hold one or two surprises in store for us. One thing is certain: plastics will definitely be part of this development!
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Simone Ernst (Editorial team K-Mag)