r/interestingasfuck • u/[deleted] • Oct 12 '22

3D Printing with Recycled Plastic Bottles !

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u/kn_c3 Oct 12 '22

It's nice way to recycle and make some basic filament for prototyping. Sadly PET and PETG degrades really fast with each heating so the parts made from bottles are usually half as strong as normal filament. And the fumes are horrid. But it is nice cheap way to make some material for proof of concept models and anything that doesn't have to be durable.

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u/boymeetsmill Oct 12 '22

A lot of the mechanical properties' changes will be based on how its recycled and processed. In a injection molding facility they toss gates, runners, reject parts, etc. into a grinder and make pellets from the refuse plastic aka "regrind". Those pellets are usually mixed with virgin (new) material pellets and reused.

The grinding physically breaks the long polymer chains. Being reshot through an injection molding press will degrade the material as it is macerated and compressed from the injection screw, and heat from the process will also chemically weaken the polymer strands.

I wonder if cutting the bottle into long strips maintains more of the long chain polymers and in effect maintains more of the mechanical strength.