2018 World Cup: plastics speed up the game
Bio-sourced football, Pebax resin soles, the grip on goalies’ globes, and others: polymers are unavoidable in football. They can be found in the full range of equipment intended for professionals and amateurs alike.
Polymers stay on the ball
It has almost become a mascot in and of itself: every four years, at each World Cup, FIFA selects and suggests a new ball. It may seem insignificant, but each time it is a small revolution that ignites the world of football, as one of those balls has yet to satisfy everyone. Of course, it is not its appearance that is polarising, but rather its behaviour in the air or when bouncing, which depends entirely on the materials used and the manufacturing technique. As we all know, a football is made up of different parts, so it is not a perfect sphere. However, it is nevertheless a far cry from the old, heavy and unpredictable leather balls. Around forty years ago, the ordinary ball became a high-tech object due to its shape and the materials used to make it.
Plastics at the top of their game
The first evolution took place at the dawn of the 1970s with the Telstar, the ball manufactured by Adidas for the World Cup in Mexico. Around twenty separate parts, called panels, made from leather and stitched together created a shape that would become famous: the truncated icosahedron. The first icosahedral ball, the Telstar is close to the shape of a sphere. Its black and white colours were not selected at random. They were chosen to make the ball more visible on the black and white television sets still used at the time. In fact, that is where it got its name, as Telstar is short for “Television Star”! The only issue it had was that the stitching had a tendency to rip without warning due to the hardness of the leather.
|Manufacturing processes and the materials used to make the balls have changed significantly since the first World Cup in the 1930s.|
At that time, equipment manufacturers began investigating plastics as a possible replacement for the leather used to make balls. They found these were more malleable, more elastic, more resistant and less expensive. Polyurethane, a very strong polymer that is easily bondable, caught their attention. This was to be a true revolution! The polymer’s fineness and the increased precision when cutting (from millimetres to microns) would enable engineers to more closely approximate the shape of a sphere when designing balls. However, polyurethane would only officially replace leather in 1986. The number of panels would also change: from thirty-two panels in the 1930s to twenty panels in 1970 and just six at the last World Cup. Since it has no bumps, the ball rolls better and floats better. Another advantage to the polymer is that it instantly regains its shape after a strike, no matter how strong. And, thanks to the glue, an aqueous dispersion of polyurethane, the ball is perfectly watertight and does not get any heavier even when soaked in pouring rain.
|Telstar 18, 2018 World Cup: the first football made from bio-sourced plastics such as EPDM.||
The Telstar 18 football goes green
Football fans will have caught the reference. The ball selected for the World Cup in Russia bears some similarities to the iconic Telstar ball from 1970. A nice tribute to the ball that changed the game. However, the similarity is only skin deep, even though the Telstar 18 (the current ball’s name) also heralds significant technological progress. The shape of the panels has changed, but that is not the most important thing. The true innovation lies in the polymer used: Kelkan Eco, a bio-sourced plastic developed by Arlanxeo, a joint venture between the German Lanxess group and the Saudi chemicals manufacturer Sauri Aramco which specialises in elastomers.
Adidas, the ball’s manufacturer, selected a material called EPDM, a bio-sourced elastomer made from ethylene derived from sugar cane for its elasticity, resilience (its ability to regain its shape) and strength. As ever, this new ball is the subject of much commentary around the world of football. Its optimal bouncing performance and its “floatability” should speed up the game and lead to more goals, which does not please all goalkeepers. How will this play out in practice? We will have to wait until the end of the World Cup before drawing any conclusions.
Polymers lend a hand
More powerful, better floating…the new ball will undoubtedly be an extra worry for goalkeepers who, given that they are particularly exposed, have to protect themselves to avoid injury. A football can reach speeds of 120 km/h (i.e. a weight of 180 kg) during penalty kicks. Needless to say, these doormen need Kevlar muscles to avoid injury. They have their own special equipment which differs not only by its colour. First all, they have special gloves. For amateurs, and possibly for professionals too, choosing the right glove is quite the challenge given the large number of different models available: one range adapts to humidity (which makes sense, since the ball is very slippery when it is raining, and others adapt to different types of pitch (which also makes sense because the ball will behave differently), among others.
|Which polymers are used for the grip on goalkeepers’ gloves? A closely-guarded secret…|
Overall, a glove must enable its wearer to grip the ball, but it must also absorb impacts and, finally, it must not hinder the goalkeeper’s movements. This is why gloves must be made of various materials. They are made of various polymers such as polyurethane, polyester, polyamide and elastomers such as elastane or natural latex. Not much more is known since there is fierce competition in the field and each manufacturer has their own recipe. What we know for sure is that the secret to a good glove is the material’s ability to grip the ball, which is down to the nature of the polymer used. All that we know is that the polymer used to make that materials is enriched with adhesives. The simpler bars that protrude from the back of the gloves intended to enable the player to send the ball back with a punch are, in most cases, made from polyurethane due to its ability to absorb and withstand impacts. The same material covers the goalkeepers’ kits to protect their chest and elbows.
|Football boots are entirely made from polymers (mesh, elastomers, etc.)||
Plastics get on their feet
Choosing a glove can be quite a challenge, but that’s nothing compared to shoes! There are also models for all tastes or rather all types of players: ultra-light shoes for strikers who need to run as fast as possible with the ball at their feet in order to score, reinforced shoes for defenders who must intercept fast balls or tackle opponents, and finally technical shoes for midfielders who need to make passes with surgical precision.
In short, quite the quagmire for novice players looking to buy their first pair of shoes! It is hard to imagine the amount of research, technology and testing that went into making those shoes from which we ask combinations of properties that are not always compatible. However, modern shoes have many points in common, regardless of the type of player for which they are intended. First of all, no offense to fans of Pelé, Cruyff et al, almost no leather is used in modern shoes.
The upper on high-end models is made from a mesh material. This breathable material was initially designed for marathon runners then, its strength having been deemed satisfactory, it was adapted to football boots by tightening the mesh a little. The mesh is in fact a polyester fibre in a polyurethane matrix. Thanks to this mesh, a shoe can weigh less than 200g, studs included. In addition, the mesh is hydrophobic: the shoe will not get heavier when wet in rain.
German manufacturer Adidas even made headlines by launching the first boot without laces in 2014. A marketing ploy? Not just that, because the brand’s technicians found that shoelaces and the eyelets can lead to losing control of the ball. They therefore improved the mesh by giving it improved elasticity in order to provide maximum hold for the foot. The areas with which the ball is struck were reinforced with an even tighter version of the same textile.
Soles bite down into the ground
Soles have also received their share of attention. The soles on mid-range models are most often made from polyurethane, sometimes reinforced with carbon fibre inserts. However, the true revolution came from French manufacturer Arkema which developed the Pebax resin, a high-performance elastomer which was instantly adopted by major sports equipment manufacturers. This polymer, which has been constantly improved over time, is lightweight, supple, flexible, strong and active as it is able to restore energy when striking. It is in fact a mixture of polyamide for rigidity and polyester for flexibility. Unfortunately, that is all we know about the material because those who have the recipe for such a successful product are understandably loathe to share it! Currently, over 50% of the players selected for the World Cup have boots with Pebax resin soles, and 80% of the goals scored during the World Cup in Brazil were Pebax Powered®!
|Pebax resin soles are now found on all the best football boots.|
Given that they are a crucial component of football boots, the studs are now moulded at the same time as the sole, provided that the latter is made from polyurethane. This is not yet the case for Pebax resin sole as the polymer is still deemed too flexible to mould studs. In the latter case, the studs are moulded from a polyurethane selected for its excellent resistance to abrasion. They are then glued onto the soles. The main advantage of these studs lies in their moulding. Polymers are known for their ability to take on all shapes. The studs were originally conical in shape, and it is now possible to find triangular, bladed and comma-shaped studs. What is the reason for such variety? Because, although studs must, first and foremost, ensure good grip on the pitch – which conical studs do very well, they must not hinder the players, which they are not so good at. The issue lies in the different balance needed depending on the type of play (running, accelerating, dribbling, etc.); studs that sink into the pitch too much while dribbling will cause the player to lose the ball, or suffer a sprained ankle. As a result, some studs provide grip, other stabilise, others help to orient the foot. And all of that because polymers can be easily moulded and have a certain elasticity that is useful for improving performance.