Eli5 why can’t tires be melted down and reused?
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Modern tires have to be able to withstand high heat from friction. Therefore, they use “vulcanized” rubber–a process invented by Goodyear long ago that changes the chemical makeup of the rubber. Vulcanized rubber cannot simply be easily melted down as regular rubber can.
Tires don’t melt. They’re made of vulcanized rubber, which is a ‘thermosetting’ material—it permanently solidifies when it’s exposed to heat & pressure. This is different from thermoplastic materials, which melt under heat and solidify when cool.
They can be shredded and used in road surfacing
https://newatlas.com/environment/recycled-tires-road-asphalt-uv-damage/
They can be retreaded although I think this is only done for truck tires. The remaining old tread is removed and the inflated tire is trued on a big ass lathe. Then a thin layer of uncured rubber is placed between old tire and new tread and the heat and pressure are reapplied. I think I learned this on a How it’s Made episode.
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Different type of rubber. You’re basically asking why we can’t melt left over bread to turn it back into dough and make new bread. It doesn’t work like that.
Tires are not one singular form of rubber and are also made up of multiple materials. They have metal, fibers, rubber, and other chemicals in them so you would need to separate all that out. Also while it may seem like it’s all solid rubber it’s actually many different formulations of rubber that do different things for the tire that get pressed together to make the tire so melting it down would end up with all that mixed together.
Not saying it’s not possible I’m sure someone could figure it out but tires are not as simple as they seem so it’s harder than it appears to recycle them.
They will be able to soon. The plan is for them to be 100% renewable in 7 years, meaning the whole tire including the cable is broken down for use. I think Michelin is at 50% right now.
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I just want to mention that plastics and rubbers and stuff are not simply stuff melted together. Melting and burning changes the stuff chemically. There are some plastics that can be molded and reset with heat, but only so many times and they take damage every time. Like stress fatigue, the way water carves rock (that’s an analogy, water doesn’t carve rock but rather erosion).
Vulcanized rubber tires are formed out of several materials, structured composites really, and then cooked with other chemicals and such, like a recipe, and the order they were made mattered greatly. So you can’t really melt it all down and reform it and expect it to be the same. I can’t think of anything cooked that adding more heat makes it go fresher again.
If you remember basic chemistry, there are physical changes (reversible) and chemical changes (generally not reversible). Making tires is a chemical change, and so is melting them.
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