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This article details the effect that basketballs have on the environment. The main component examined is butyl rubber.

Overview of importance

Millions of basketballs are disposed of every year due to general wear and tear, damage to the internal bladder, or simply upgrading to a new and better basketball. 450 million people in the world play basketball on the competition or grassroots level. Since the average basketball contains about 10 oz of butyl rubber,if every one of these players throws away even one basketball 3 year span, this amasses 281,250,000 pounds of butyl rubber waste! This number may seem high, but estimating only one basketball thrown away per player is extremely conservative. Almost all basketballs are composed mainly of an internal bladder with outer surfaces composed of varying materials. These bladders are almost universally made of the same substance . There are many characteristics that the bladder substance must have which are why all bladders are made of the same substance. This substance is Butyl Rubber. Since butyl rubber is the sole material used to make the basketball bladders , when basketballs are thrown away, butyl rubber is thrown away in the process. If even harmless materials can make a difference in large amounts, millions of pounds of a substance as interesting as butyl rubber can have a serious impact on the environment.

Natural rubber

Poly(cis-1,4-isoprene) = natural rubber

Natural rubber consists of C₅H₈ units, each containing one double bond in the cis confirmation. The Vulcanization process made both cis and trans possible. Synthetic rubber is much more desirable for industrial/human purposes.

Butyl rubber

Pictured is the chemical structure of butyl rubber

The bladders must be made of a durable substance that is light enough to bounce but strong enough to retain its shape. The bladder must also be airtight. Butyl rubber, also known as isobutylene-isopropene rubber (IIR), is universally used to produce basketballs for these reasons. The same characteristics make it a great candidate for use in tires and other applications. Butyl rubber is valued for its chemical inertness, weatherability, and impermeability to gases. Butyl rubber is synthesized and processed precisely to accentuate all of these characteristics. Unfortunately, the same characteristics that make it great for bladder production make the synthetic rubber extremely tough for the environment to break down. Millions of pounds of a substance that is not easily broken down can take a heavy toll on the environment.

Butyl rubber synthesis

Butyl rubber (IIR) was first synthesized in 1937. The Copolymer is formed by copolymerizing Isobutylene with small amounts of isopropene makes IIR. Isobutylene and isoprene are usually obtained by from natural gases or lighter fractions of crude oil through thermal cracking. At normal temperature and pressure isobutylene is a gas and isoprene is a volatile liquid. Isobutylene must be refrigerated to around −100 °C because it is such a volatile liquid and is a gas at normal temperature and pressure. The copolymerization reaction occurs when low concentrations of isopropene are added in the presence of aluminum chloride. This is not the end of the process.

Once the butyl rubber has been copolymerized, it is then “vulcanized” to even further accentuate the favorable characteristics . In many occurrences, the butyl rubber has already been formed into bladders when vulcanization takes place. During vulcanization, the rubber is heated and subjected to intense pressure that makes it stronger, flexible, etc. The vulcanization process is also responsible for the basketball bladders being very airtight. Mechanically, the process described above is simple. Chemically, it is a little more complex.

Vulcanization can also be described as a chemical process for converting polymers into more durable materials by adding curatives. The main curative used in basketball bladder production is sulfur. These additives form crosslinks between the individual polymer chains. These crosslinks, or bridges, make the product much stronger as described in the mechanical process.

Allylic hydrogen atoms are what drives the sulfur addition vulcanization chemical reaction. Because these carbon-hydrogen bonds are adjacent to double bonds between carbons, chains of sulfur atoms replace some of these carbon during vulcanization. The same sulfur chains can carry out the reaction with another polymer chain to form the crosslinks, or bridges. The number of sulfur atoms in the crosslink can vary. The number can be as big as eight or as small as one. This number has a huge impact on the final physical properties of the vulcanized rubber.

Butyl rubber’s resistance to environmental breakdown

IIR is as strong as natural rubber. This is based on several chemical factors. Butyl rubber’s base polymer is polyisobutylene, which is stereoregular. Stereoregular polymers have an ordered arrangement of pendant groups along the chain. Stereoregular polymers are usually very strong. These polymers can be packed much closer together because of their simple and uniform structure. This usually ensures a high degree of crystallinity.

All of these general descriptions of stereoregular polymers also describe butyl rubber, but the butyl rubber copolymer does not contain many unsaturated groups. Unsaturated groups mean double bonds between carbons in this case. More specifically, the only carbon-carbon double bond is located between located in each isopropene repeating unit . This lack of unsaturated groups may be the most important aspect of the chemical structure. It is certainly one of the most important aspects in relation to environmental breakdown.

Materials in the environment are generally degraded by oxidation. Butyl rubber is very resistant to this process. In oxidation, oxygen in the atmosphere breaks the polymer chains by reacting with the double bonds to degrade the material. If the IIR does not have many carbon-carbon double bonds for oxygen to attack, it will sit in the environment without being degraded for much longer periods of time. IIR is not only resistance to attack by oxygen; it is also very resistant to ozone attack. The copolymer has an incredibly low rate of molecular motion. This contributes to its ozone resistance. This is directly related to butyl rubber’s impermeability to gases. It is tough for the gases in the environment to break down the very material that is synthesized and altered to avoid gas-attack related breakdown.

Environmental impact

The environmental impact of basketballs on the environment is not complicated to understand. However, it is difficult to raise alarm about the impact basketballs can have on the environment because the main material used in not necessarily “harmful” to the environment. The impact basketballs can have is the amount of space they can take up in landfills. Millions of pounds of butyl rubber are thrown out each year and almost all of it could be recycled and used again. This is apparent because bladders that have been vulcanized, but are not deemed strong enough or impermeable enough are all recycled right back into the synthesization and vulcanization process. Some man-made materials are extremely difficult to recycle. Valuable landfill space should not be taken up by millions of pounds of valuable and usable resources. Also, each pound of butyl rubber that is not recycled means that another pound must be synthesized to take its place in the never-ending cycle of basketball production.

Degradation in the environment

Synthetic rubber can be broken down and oxidized by the environment. This process can be sped up which will reduce the time that rubber sits in landfills. Butyl rubber can broken down physically or chemically. Physically, bladders are ripped naturally in the environment. Some bladders already have rips and holes when they are thrown out. Chemically, research indicates that microbes can begin the biodegradation process.

This diagram describes the chemistry of the described pathway for rubber biodegradation via Streptomyces

Rubber biodegradation

Research indicates that certain Streptomyces species can degrade rubber into forms that more readily undergo oxidation by the environment. This process is slow because these organisms are slow growing. These organisms are not always abundant in areas where basketballs have been thrown away.

Butyl rubber recycling efforts

There is a significant amount of butyl rubber recycling, but almost all of the recycled butyl rubber comes from automobile tires {. The recycled butyl rubber yields rubber scrap. It is often used to reduce noise pollution, but many manufacturers buy the rubber scrap to use in manufacturing their products {. It is preferred because it is much cheaper and, after more vulcanization, still performs as well as newly synthesized rubber {. Obviously, using recycled rubber scrap is better for the environment because it reduces waste.

Basketball recycling

Basketball is a flashy game. In many college and professional leagues, a new ball is used for every game. Using the same ball for multiple games would reduce waste, but basketball recycling has much more potential. Companies like Wilson and Spalding already sell basketballs made from up to forty percent recycled rubber. The higher this percentage gets, the more waste that is being reduced.

Conclusion

Basketball manufacturing companies increasing the amount of recycled butyl rubber used in their basketball bladders would significantly reduce the amount of wasted butyl rubber . There will always be some loss and waste, but recycling even half of all butyl rubber bladders would remove millions of pounds of waste from the environment. Recycled rubber scrap is bought for significantly cheaper prices than new synthetic butyl rubber, so money is not an obstacle . Butyl rubber is such a perfect material for making basketballs that it is unlikely that a new material be made in the near future. This has not raised significant scientific alarm as butyl rubber has not been found to be especially harmful to the environment. However, Butyl rubber simply sitting in a landfill somewhere is a waste of environmental space and chemical synthetic resources. Recycling basketballs and, therefore, butyl rubber would reduce the amount of butyl rubber that needs to be synthesized. Basketball is one of the fastest growing sports in the world. Recycling basketballs used by the 450,000,000 basketball players worldwide has the potential to eliminate hundreds of millions of pounds of basketball per year.