Eli5 why can’t tires be melted down and reused?
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ELI5 version: vulcanisation of rubber is a one way chemical process.
However, Tyre manufacturing is an awesome industry and it’s really interesting, so to give a bit more than an ELI5 version.
Modern tyres are made out of a bunch of smaller components, from silica to natural rubber to synthetic rubber to different rubbers from different regions. Modern tyres can have 100s of individual components just in the rubber compound alone.
Rubber undergoes a process when heated called vulcanisation which changes it from its natural liquid state too the rubber you know today in balls and tyres and toys.
That vulcanisation process combines all of the ingredients together and cooks them like a big cake, and the process is non reversible.
Big tyre manufacturers today like Michelin are working on making their tyres as recyclable as possible, with their new line of Pilot sport 5 tyres being approximately 20% recoverable or recycle-able components, and a goal that by 2050 all of their tyres will be 100% either recycled or recoverable or recycle-able.
At the moment the main things that can be recovered are the oils and some of the synthetic components.
[this video from Michelin](https://youtu.be/Drk0o9FIAhQ) shows the process and the difficulty in much more depth. It’s fascinating stuff.
Long term though the real plan will be for tyres to be non-pneumatic (no air in them) and 3D printable [here is a video from 6 years ago showing this concept in action](https://youtu.be/Tyc4Apyk2Rc)
The idea then would be that your tyre shop prints your tyre, and as you run through it, they simply print new layers onto it.
While you still lose some components to heat and friction, the majority of tyre waste is the carcass, which these revolutionary new designs hopes to fix.
In the truck world we allready have regroove and retread which lets one carcass live 5-10x it’s normal lifespan, dramatically reducing environmental impact and improving longevity.
Unfortunately due to consumer perceptions around retreading and car manufacturers wanting lower and lower profile tyres, regrooving and retreading passenger tyres will likely never happen.
(I work in the tyre industry, and no, I am not fun at parties unless you like manufacturing)
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