#110 Why Are Tires Black? The Chemistry of Durability and Recycling
In this episode, we focus on cars and dive into the chemistry behind those round, black tires everyone has seen at least once.
Tires were not originally black by nature.
Actually, the sap from natural rubber is milky white, much like cow's milk. So, why are tires pitch black? It turns out that a very fine carbon powder called "carbon black" plays a crucial role. It is not merely for coloring; it is fascinating to learn that it is kneaded into the rubber to dramatically increase its strength.
Tires are made of components other than just rubber.
It is easy to assume that tires are simply blocks of rubber, but by weight, they contain only about fifty percent rubber. The other half consists of the aforementioned carbon black, reinforcing materials, copper wires, fibers, and sulfur. This precise composition is what provides the strength needed for tires to withstand harsh road conditions.
The price of durability is a barrier to recycling.
The process known as "vulcanization" used to make tires durable is actually the very factor that makes recycling them difficult. Once the molecules are linked together with sulfur, they cannot be melted down and reshaped by heat. We touch upon the current mainstream recycling methods and the challenges involved, so please be sure to enjoy the full episode to learn more.
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