thermoplastics recycling
Why they are not infinitely recyclable in practice
Here’s where the gap comes in:
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Thermal & mechanical degradation: Every time you heat, shear, and re-extrude a plastic, the long polymer chains break down a little (chain scission).
- This reduces molecular weight → makes the material weaker, more brittle, or yellowed.
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Additives and fillers: Most plastics have stabilizers, pigments, plasticizers, or fibers mixed in. These don’t “reset” when you recycle and can accumulate problems.
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Contamination: Mixing different plastics (say PET and PVC, or PE and PP) makes recycling streams incompatible, lowering quality.
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Downcycling: Instead of making “new bottle from old bottle,” many plastics end up as lower-grade products (e.g., PET → textile fiber).
So practically, a thermoplastic can often only go through ~5–7 recycling loops before it’s too degraded to be useful.