There are many materials that are utilized to create or manufacture basketball shoes, but only a few are considered more popular and commonly used compared to the others. One of these materials is polyurethane, also known as PU, and you would often see this material used as the midsole or outsole of classic and modern basketball shoes.
While we often see and wear basketball shoes with polyurethane midsoles, a lot of us don’t really know what polyurethane is. To learn more about this material, here are details about polyurethane and how it is used in basketball shoes.
What is Polyurethane?
Polyurethane is a class of polymers, a substance that consists of large molecules that have many repeating subunits and are described to have toughness and elasticity. The polyurethane plastic material can come in various forms, as it can be customized or formulated to be more flexible or rigid, depending on how it is used.
Besides basketball shoes, polyurethane can also be found in building insulation materials, insulation for freezers and fridges, soft mattresses for beds, car parts, and cushioning for various pieces of furniture. Polyurethane is also used as adhesives or as a material for rollers and tires. However, the most common item made of polyurethane that you would usually see in every household is the kitchen sponge, which is used to clean dishes and utensils along with dishwashing liquid.
How was Polyurethane Invented?
The very first polyurethane material was created in 1937 by Otto Bayer, a German industrial chemist, along with his coworkers at IG Farben, a chemical company located in Leverkusen, Germany. The new polyurethane had several advantages over other plastic materials that were available during that time, and these advantages include being easier to manufacture, more durable, and more flexible to mold for custom shapes and sizes.
By the start of World War II, polyurethane would be used as flexible material for aircraft coating. Because of the popularity and inexpensiveness of polyurethane after the Second World War, the material became commercially available in 1952.
How is Polyurethane Used for Basketball?
In the basketball court, polyurethane is not only found in the shoes of the players, as the actual basketball or the ball used to play the sport would often have a top coat of polyurethane that serves as protection for the finish or color of the ball and also against scratches, dings, and other types of damage.
However, the polyurethane topcoat is only found in balls used for indoor basketball, as the one used outdoors is actually made of synthetic leather that has polyurethane in it. The reason why outdoor basketballs are made from polyurethane synthetic leather is that the material is tougher and more durable, so they are more suitable for outdoor basketball courts that are made of concrete and are quite rugged.
In addition to basketballs, the seats of the audience would usually have foam made of polyurethane too. The polyurethane foam in premium courtside seats and the seats used by basketball players on the bench is typically memory foam, which is a type of cushioning that has high density but is soft enough to be form-fitting and supportive for your bottom. However, there are also polyurethane foams in basketball court seats that are not memory foam but are still comfortable enough for sitting.
Polyurethane on Basketball Shoes
Applying polyurethane as a midsole for basketball shoes became quite popular among many shoe brands from the late 1980s up to the 1990s. One of the reasons why polyurethane is popular in footwear is because of its comfort, as it is noticeably softer than other types of plastics that were used for midsoles before the late 80s. However, despite being soft, polyurethane is actually quite durable, so it wouldn’t really bottom out quickly compared to other softer materials.
Polyurethane was incredibly easy to manufacture for footwear during those periods as well, as the material is flexible enough to be molded or developed into different midsole and outsole shapes. But, besides midsoles and outsoles, polyurethane is also used as an insole for some basketball shoes for extra comfort.
However, by the 2000s, polyurethane would fall out of popularity in favor of EVA (ethylene-vinyl acetate). EVA is a copolymer that is said to have the same cushioning capabilities as polyurethane but is better at shock absorption and is much more durable. EVA would be improved further through the creation of phylon, a type of midsole that is created through the compression of EVA. Phylon is supposed to be denser and more comfortable over a longer period of time compared to regular EVA.
Because some of the classic basketball shoes have polyurethane midsoles, like some of the Air Jordan models, the material is still abundantly used by various brands today. But, basketball shoes with polyurethane midsoles are just used for casual wear today since there are now better and more advanced midsoles develop that are more durable and comfortable.
The Drawbacks of Polyurethane
Other reasons why polyurethane isn’t used in modern basketball shoes anymore are related to its degradation over time. One of the signs of the degradation of polyurethane is when it becomes yellow, which happens when it is exposed for a long period of time to sunlight or UV rays. So, from the normal white or off-white color of polyurethane, it would eventually turn into a reddish-brown or yellow color, which doesn’t look appealing for a lot of basketball players and fashionistas that like to have basketball shoes for casual wear.
Furthermore, polyurethane is also very prone to crumbling when it absorbs too much moisture in the air. This reaction is called hydrolysis, which is a process wherein an organic chemical like polyurethane has a severe reaction to water. In hydrolysis, the polymers or large molecules or the material would break down into monomers or small molecules, which would then result in the crumbling of the material due to lack of structure.
These are the pieces of information that you should know about polyurethane and its use in basketball shoes and other applications. If you have a pair of shoes with polyurethane midsoles, you can make them last longer by storing them away from sunlight and not exposing them to too much moisture and humidity.