Bend it like PU – Plastics in sport

Today, no one can imagine leather balls, wooden rackets, bamboo poles or cinder tracks in sporting competition. Natural materials have now been almost completely replaced by other materials: plastics. They are light, robust and highly functional. Thanks to intensive research, they are also becoming more and more efficient – and ultimately lead to new world records.

Today, sport and plastics are inextricably linked. But that was not always the case: billiard balls used to be made of ivory. To meet the demand, about 120,000 elephants were killed every year. Then, in 1863, Michael Phelan offered a prize of $10,000 for an alternative to ivory. A few years later, John Wesley Hyatt developed one of the first plastics: celluloid. Billiard balls were never made of celluloid, but of phenolic resin, but table tennis balls were.

Even though plastics have long since found their way into our everyday lives, they were far from being commonplace in sport. In the 1980s, the Swede Björn Borg was still an ace on the tennis court with his wooden racket with strings made of natural gut. Today's tennis rackets are made of carbon fibre reinforced plastics (CFRP). They are lighter, more manoeuvrable and at the same time more robust than their predecessors – and are partly responsible for the fact that the serve of today's tennis professional is about 28 km/h faster than that of a tennis professional of that time. The fastest measured serve was achieved by the Australian Sam Groth in May 2021 and amounted to 263 km/h.

Many sporting world records would not have been possible without plastic. At the 1952 Olympic Games, the American Bob Richards jumped 4.55 metres with a bamboo pole. In 2021, the Swede Armand Duplantis reached over 6 metres – with a pole made of CFRP. Also at the 1952 Olympics, a wooden javelin flew 73.78 metres, which won American Cy Young a gold medal. Today's world records are just under 100 metres – set with javelins made of glass-fibre reinforced plastics (GRP).

A famous example of a piece of sports equipment made of plastic is the football. In the past, people played with a ball made of sewn-together leather honeycombs filled with a rubber bladder. Today, that is hardly conceivable. For fair competition, it is important that the ball does not absorb rainwater and that it returns to its original shape after a kick, which enables a precise trajectory. This is achieved thanks to polyurethane (PU), the material from which official match balls are made today. In most cases, nothing is sewn any more, but is heat-bonded in a special process called thermal bonding. This makes the ball not only durable but also highly symmetrical.

Natural materials have now also been replaced by plastics in water sports. Today, sailing yachts are largely made of CFRP or GRP. The hulls of the yachts can thus be made particularly light and robust at the same time. Special antifouling films made of silicone protect the hull from algae and mussel deposits.

In swimming pools, the material – in addition to contact with water – is exposed to chlorine for a long time. Plastics such as the copolymer Polystone from Röchling not only withstand this over the long term, but are also easy to clean and UV-resistant.

Today, sportsmen and sportswomen are dressed in plastic almost from head to toe. This is because functional clothing made of plastic fulfils an elementary requirement: it is warming in the cold and cooling in the heat. In addition, the breathable, lightweight synthetic fibres ensure that perspiration is not absorbed but released to the outside. Friction is also reduced thanks to functional clothing. They fit the body like a second skin and provide optimal freedom of movement.

For winter sportsmen and women, the head is also made of plastic: professional helmets are usually made of the very light material carbon on the outside. On the inside, expanded polystyrene (EPS), for example Styrofoam, is used. This can deform in the event of a fall and compensate for the impact forces.

Today, sports shoes hardly contain any natural fibres or leather. Upper materials, soles, insoles – all components of a sports shoe must be light, durable and efficient. Plastics meet all these requirements. Silica technology, which also helps car tyres to grip better, provides a firm hold. And thanks to the cushioning properties of certain rubbers, joints are relieved and protected.

Research is constantly being conducted into new plastics and technologies to provide even more comfort and performance for the wearers of shoes. BASF has developed a foam made of a new expanded thermoplastic polyurethane (E-TPU). According to the manufacturer, Infinergy is elastic like rubber, but resiliently light. The material is used in the adidas Boost. The midsole of the running shoe consists of 2,500 E-TPU capsules, which pop up like corn kernels when you run and increase their volume tenfold. With the help of this technology, the runner receives an energy recovery and thus a boost.

Sustainability also plays a role in the new developments. Adidas, for example, spent almost a decade researching to finally bring a running shoe to market with the UltraBoost DNA Loop that is completely recyclable for the first time – true to the motto "Made to be remade". It consists entirely of TPU – from the sole to the laces. By the way: BASF's Infinergy material is also used in this model.

The list of sports equipment made of plastic is, of course, much longer. Whether in tennis, football, water sports or athletics – today's sports equipment has very little in common with what it used to be. Thanks to plastics, rackets, balls, clothing and co. are becoming lighter, more flexible and at the same time more robust. This increases the performance and comfort of the athletes. Plastics have made today's world records possible in the first place.

Or as the German 400-metre hurdler Harald Schmid aptly summarises: "Plastics have revolutionised sport!"