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What do the recycle numbers mean on plastic bottles?

Polymers in and Around You Read more from
Chapter Polymer Chemistry

These are technically called Resin Identification Codes (RSI) and were introduced in the 1980s to make it easy to separate plastics for recycling. The numbers correspond to what kind of polymer the item is made of and have no other meaning. They are not in any sort of order based on how easy or hard it is to recycle the resins, despite rumors you might have heard about this.

What do the recycle numbers mean on plastic bottles?

These are technically called Resin Identification Codes (RSI) and were introduced in the 1980s to make it easy to separate plastics for recycling. The numbers correspond to what kind of polymer the item is made of and have no other meaning. They are not in any sort of order based on how easy or hard it is to recycle the resins, despite rumors you might have heard about this.

RSI Plastic
1 Polyethylene terephthalate
2 High-density polyethylene
3 Polyvinylchloride
4 Low-density polyethylene
5 Polypropylene
6 Polystyrene
7 All others

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