; Date: Sun Aug 11 2019
It's fairly easy to melt down plastic bags, of the right type, and in a mold make a strong material that's like marble. Basically one gets a large quantity of plastic bags, or other plastic, puts them in an oven for melting, then pours the "dough" into a mold. After the plastic has cooled and hardened in the mold, it can be processed using metal or wood working tools like sanders and polishers.
The process is similar to an earlier how-to: How to recycle HDPE plastic to make DIY raw material for art projects
The first step is collecting a bunch of plastic bags. The Polish text at the bottom says to use LDPE or HDPE plastic bags. Bags will not always be marked as to their type.
Next you cut them into small pieces. The attached video is shot in a facility set up as a machine shop, and therefore they have machine shop tools available. It may be possible to use a paper shredder to shred the plastic bags, or as the video suggests you can cut them with scissors.
Next you need an oven that can be set to 200 degrees C - that might be 400 degrees F. Again, the video shows an industrial oven, but a regular household oven should be fine.
The video does show using a face mask to avoid fumes.
A simple metal bowl is enough to handle melting the plastic. As it melts it will form what the presenter calls a "dough". In another article we show plastic being melted on a baking sheet, and it forming a substance that could be called "dough". How to recycle HDPE plastic to make DIY raw material for art projects
When you've melted enough plastic it's time to pour into a mold. Again, they're in an industrial setting and have an industrial-type mold. It'd be possible to use other kinds of objects as a mold, and to use baking paper to line the mold.
After awhile the object will have cooled and hardened enough to remove from the mold. The surface will be rough meaning to make it look nice the surface should be prepared. The plastic object will be hard enough, and strong enough, to process using power tools.
The video shows different sorts of milling machines, sanding machines, and polishing machines, to give the plastic object a good finish.