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Skip to 0 minutes and 6 secondsSports equipment is continually evolving. Traditionally, sports equipment was made from natural materials, such as metals, wood, twine and even ox-gut. The limited supply of these materials meant that only a small proportion of the population played sports. Today, chemists have developed new, cheaper synthetic materials, which allow most people to play. The new materials also enhance the performance of those playing sport - for example, polymers combined with natural compounds from rubber have been used to create golf balls that travel a greater distance, have higher abrasion resistance, and improved firmness. We will see that nanomaterials, including carbon nanotubes, are now being routinely incorporated into various sports equipment to add extra strength and stiffness, durability and to reduce weight.

Skip to 0 minutes and 59 secondsAlthough polymers and synthetic materials are most often associated with the equipment and clothing worn by competitors there are, in fact, many additional, supporting uses for polymers. These range from applications in playing surfaces, balls and pucks, to waterproof clothing for spectators and fans. Synthetic playing surfaces are incorporated into many professional leagues including the NFL (American football), EHL (Field Hockey) and International Tennis Opens. On AstroTurf pitches linear low-density polyethylene (abbreviated as LLDPE) is used. LLDPE retains a similar structure to low-density polyethylene (LDPE) but mixes 1-butene monomers with ethene monomers in order to produce a more ordered structure. Meanwhile, for tennis and similar court sports, an ethylene-propylene-diene backbone, incorporating an ethylidene norbornene structure, is used.

Skip to 1 minute and 57 secondsThis forms an elastic polymer, which gives courts grip for competitors and increased bounce for tennis balls in order to provide the best performance possible.. In order to reduce bouncing pucks during ice hockey games, pucks are kept in freezers as they are made of vulcanised rubber that becomes more elastic when warmed. Vulcanised rubber consists of a rubber polymer of cellulose or isoprene, which has been treated with sulfur under high pressures and temperatures. The result is a durable structure of cross-linked polymers that are rigid and durable. Wimbledon championship tennis balls undergo an even more rigorous pre-game warm-up where they must adhere to hand-tested bounce, weight and compression guidelines. Their protective felt coating is often made from dyed wool or synthetic nylon.

Skip to 2 minutes and 49 secondsBoth polymers contain amide bonds. The properties of some polymers allow for them to work under high stress and pressure whilst maintaining their shape. As such they are essential materials in high performance sports where other compounds would be unable to hold their own. For example, PVC (poly(vinyl chloride)) has a similar structure to polyethene except for a single hydrogen substituted for a chlorine atom. Over 140,000 m2 of PVC was used in the construction of venues for the London Olympic Games, comprising of flooring for basketball, badminton and table tennis courts as well as roofing and canopies in stadiums. High performance PVC crashmats are used in martial arts to provide a tear resistant surface under which impact padding can be layered.

Skip to 3 minutes and 40 secondsAlternatively, Zylon is an integral component of high-performance sails. It has high tensile strength and is very resistant to stress creep where materials are deformed over time. Many novel polymers and synthetic materials are first trialled in sports equipment to monitor their effectiveness against impacts, friction and stress. This allows for new materials to undergo rigorous testing whilst potentially providing a competitive edge. Only once these materials have been certified as both effective and safe for use is their incorporation into other areas, such as structural and aeronautical engineering, considered. Enhancements in sports technology are commonly adapted for public use over time, especially in sectors such as motor technology.

Skip to 4 minutes and 30 secondsNano-particles of copper oxide (CuO), zinc oxide (ZnO) and zirconium oxide (ZrO2) are used in lubricants to reduce wear and friction whilst carbon nano-fibre brakes, first trialled in Formula 1 racing cars, have a longer lifetime and provide greater thermal resistance than cast-iron brake discs.

Understanding the role of polymers in sports equipment

The optimum design of sports equipment requires the application of a number of disciplines, from anatomy to materials science, for enhanced performance and to make the equipment as user-friendly as possible, to avoid injury. In designing sports equipment, the various characteristics of materials must be considered including strength, ductility, density, fatigue resistance, toughness, modulus (damping), and cost. If we want a material that features the highest possible stiffness for the least possible weight, we would select low density materials with the highest specific stiffness.

Spandex (or Lycra®) is an interesting stretchy elastic artificial fibre. It is used to make sports clothing including wetsuits, and with other fibres to make comfortable clothing with a snug fit, that helps to support muscles. Its structure has a stretchy section that makes it soft and rubbery, and a rigid section (containing substituted benzene rings and urea, –NHCONH–, functional groups) that makes it tougher than rubber. Different chains can form hydrogen bonds (C=O IIIIIIII H–N) to one another that aligns the rigid segments in different chains in the fibres. Spandex is lightweight but doesn’t get damaged by sunlight, sweat or detergents - all of which can make other materials wear out.

The structure of spandex

To meet the requirements of sports equipment, the materials of choice often consist of a mixture of material types, typically metals, ceramics, polymers, and composite concepts. Composite materials are made up from two or more materials with different chemical and physical properties, that when combined, produce a material with characteristics different from the individual components. For example, carbon-fibre-reinforced composites makes them superior to the metals in imparting high forces to the ball. To reduce the vibration upon impact, racket handles are constructed of multiple carbon fibre-reinforced layers wrapped around a soft inner core, which is often an injected polyurethane foam or honeycomb construction. A polyurethane is formed, for example, by reacting a diisocyanate with a diol.

Making a polyurethane

In the Paralympics, some sprinters have made use of prosthetic devices featuring carbon-graphite feet bolted to carbon-composite sockets, that provides the right balance of stiffness and flex at a substantially reduced weight as compared to conventional materials such as wood. The arrangement acts like a springboard, with the runner punching the track with each step forward, catapulting the athlete more efficiently than if they were running on two human feet.

Ethical implications of emerging materials

So, amazing improvements have been made in those sports where equipment is critical. However, the use of advanced materials in sports equipment presents some ethical questions. We can clearly enhance behaviour by allowing the use of advanced materials, but where should the line be drawn, or should there be no restrictions? Can we ensure that athletes are competing and not the advanced materials? Also, should we allow competition at the highest level to be only affordable to the elite because of the high cost of modern equipment?

What do you think?

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This video is from the free online course:

Exploring Everyday Chemistry

University of York