Skipping the pellet stage


I’m just starting a project to make roofing tiles from recycled plastic and sand in Uganda. However, I want to do this with very minimal machinery and avoid the pellet stage…I’m thinking of layering thin pieces of HDPE or LDPE and sand between two hot aluminum plates and fusing the plastic/sand layers together. Does anyone have any thoughts on if this could work?

I found this post about plastic/sand tiles, but it seemed old, so I figured I’d start a new post here.

I’ve read that additives are mixed into the plastic/sand mixture to make the tiles UV resistant. Can additives work if I just heat and compress strips of plastic and sand instead of using an extruder?

Also, a lot of the companies say their tiles are flame resistant–how do they make that possible?

I attempted a trial tile in my kitchen oven with an HDPE milk carton. I’ve read all the posts about fumes and safety when melting plastic and they say that hdpe and ldpe are safe. But I smelled a bad smell and got a headache. I read the oven should be set to 350F (176 C) for hdpe and I melted it for about 25 min, taking it out a few times to check. Can you tell me why it smelled badly and why I got a headache? How can I prevent this?



Answering your last question :
> Can you tell me why it smelled badly and why I got a headache? How can I prevent this?

This might be a plastic contaminated either with additives within, or with glue/packaging/liquid residues.
PE is safe with melting temperatures ranging from 130°C to 280°C (according to the “melting temperatures” poster), so even if your oven hasn’t a precise temperature setting, 176°C should be fine.

The other possibility might be the sand itself. It might contain organic residues, salts from waters. Are you sure the sand is washed and separated from any organic/toxic substances ? Try making the sand cleaner and see if it gets rid of some of the vapors and odors 😉

For your first question about skipping the shredding phase, I don’t think it would be a good idea. PE even in melted state is still gluey with a viscosity higher than that of a liquid. PE is therefore more difficult to mix with sand.
If you have a liquid you can mix sand in it easily, but if you have something less liquid then you should grind it to a similar consistency (coarse or fine grain at least) and with some mixing (like in a concrete mixer) while heating at the same time, you’ll get good results.

Keep up the good work 🙂