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I have seen a number of videos that talk about melting down HDPE and/or LDPE for craft projects. Some say these types of plastic are safer to some extent. I would like to do some crafts as well that would use stock pieces, like the seat of a stool or a bowl.

Are other plastics (non HDPE/LDPE) just not sturdy enough to go through melting to be used or even safe? Which plastics would be food safe? In the case of making a bowl or plate.

  • Best sources of advice on this will probably be 3D printer communities. My (limited) understanding is that plastic degrades when re-heated, but I don't know if that's all plastic or only certain types. +1 for an interesting question! – Robotnik Jul 17 at 1:15
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Many plastics can be used for melting, but not all. Basically there are 2 types to distinguish here; thermoplastics and thermosetting plastics.

Thermoplastics can be heated and shaped. Examples are HDPE, LDPE, PLA, and PP (see the Wikipedia link for a longer list of types)

Thermosetting plastics harden or burn when heated. Examples are Phenolic (PF) resins, most polyurethanes (PUR) and some types of polyester.

Note that melting plastic can release toxic fumes. How toxic the fumes are depends on the type of plastic. I would not recommend melting PVC, ABS or PS. I heard mixed stories about PET, I guess it depends on the used additives. In any case make sure you have good ventilation when you melt.

Food grade plastics are plastics that contain very little contaminants like dyes or other additives. To guarantee a plastic is food safe, it's usually made from virgin (non-recycled) plastic. The exception is PET bottles. When collected separately they can be reused or recycled into new PET bottles. Whether your molded plates are food grade depends on how well you can control the temperature while melting (keep it as low as possible) and if you introduce contaminants or not. The safest to use is probably HDPE. In any case I would not put your plates in a dish washer or microwave, or use them with acidic foods like tomato sauce.

There is more information also here:

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