Instructables

How to recycle HDPE (milk bottles and caps) into usable sheet material

Picture of How to recycle HDPE (milk bottles and caps) into usable sheet material
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I discovered an easy way to recycle HDPE into small sheets of tough, rigid material, using a flat sandwich toaster.

Here's a video of the process:


And here's another showing various ways of working the plastic material:

Source material can be found in the form of plastic milk bottles (also some bottles from household cleaning supplies, toiletries).  Some bottle caps are also HDPE.

Briefly, the process comprises:

Cut the bottles and caps up into small pieces - about 1cm square or smaller is good.

Preheat the sandwich toaster (mine goes to 180 Celsius, which is perfect, as this will melt HDPE to a sticky, toffee-like consistency without burning or producing any noxious fumes).
Place a reusable nonstick baking sheet on the bottom plate of the toaster, then add a heap of HDPE fragments.  Place another nonstick sheet on top and press the toaster closed.

After a few minutes, the plastic will melt together into a rough sheet - take this out (don't attempt anything without the gloves), peel off the top layer of nonstick and fold in the edges of the melted plastic, then replace the nonstick sheet and put it all back in the toaster.

Repeat until you have a solid blob of melted plastic between the two nonstick sheets - then clamp this between two flat boards to cool.

Once cooled, the plastic will be very tough and rigid - and can be cut and shaped with hand tools, or machined.
rball93 days ago
Hi does any one have or know of a list of all hdpe sources i.e which bottles are hdpe or not as my first attempt failed due to non hdpe in the mix
os_sanches1 month ago

Hi, can this plastic be milling or machined ?

kludge77 made it!1 month ago

Thanks for the detailed video!

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huskerland3 made it!4 months ago

I made this with.. a small meatloaf tin, wax paper, cut the finished product with a saw and heat gunned a couple of pieces together and used the "crumbs" to fill in the gaps. The plan is to making a cutting board.

hdpe.jpeg
I_StarkGuy9 months ago

I don't have a flat sandwich toaster. What about using an electric stove and a flat pan and stirring the shredded plastic over the baking sheet?

You'll destroy the pan but if you don't mind.. it will work

jibblesmgee9 months ago

Since this is so slippery, would it be reasonable to make bearings from it? I mean, for light loads of course.

aaahotdog2 years ago
Very nice. My suggestion would be to use a crosscut paper shredder if available to help with the cutting of the milk cartons. It would make shredding much easier.
Atomic Shrimp (author)  aaahotdog2 years ago
Paper shredders aren't generally man enough for the job (I tried).

I did actually build a shredding device made from a Spong mincer, powered by an electric drill and gearbox - and this was reasonably successful - I had a plan to try to weld sheets of recycled HDPE together to skin a canoe (details here: http://www.atomicshrimp.com/st/content/plastic_boat/), but it was too hard to get a consistent quality on the joints

Could you cut to strips then weave them together into sheets, then paint some kind of plastic sealant over them; would that be stronger than welding flat sheets?

twopussez10 months ago

With the coloured cap chips in I think this would make a good chopping board or maybe a salad bowl. Ive look at this because Im getting a 3D printer and want to research all possible sources and safe re-uses of recycled shop bought plastic. I think I'll try to design a grinder though cos everyone asks about that yet not a single soul in a country once famous for engineering has even brought an advanced form of the Lyman bicycle gear/wiper motor filament extruder yet. Its a mystery!

Possibly a stupid question, but here goes ...

Can a woodchipper be used the cut up the plastic containers?
I ask because my hands don't hold out long when cutting up the plastic - thus little is achieved and the proccess takes a very long time.

try a blender

Lambert981 year ago
Can I use a toaster oven?
pfred22 years ago
Next season I'll have to keep my eyes open for a sandwich maker so I can try this. Although I can usually run across used HDPE cutting boards for pretty cheap. I think I paid 50 cents for the last one I bought. I am wondering if better shredding or stirring the plastic while it is molten would not make an even better quality product?

When you were sawing your HDPE and it was slipping around on you you might want to try sandpaper to keep the plastic in place.
Atomic Shrimp (author)  pfred22 years ago
I'm never sure whether cutting boards are HDPE or nylon - they're not always clearly labelled, but one of the things I like best about this recycled stuff is the scope for adding a splash of colour to the items I make.

The sandpaper idea is a great tip - thanks for that.
Nylon? That would be a jackpot! I don't think anyone makes cutting boards out of Nylon. Nylon is mighty expensive. But if you were to score a cutting board made out of Nylon then consider it a big win. Nylon is much nicer than HDPE.

Sandpaper grip is a common woodworking trick. Like you say HDPE is some slippery stuff, but sandpaper should be able to hold it. Nothing worse than trying to work on something and it is not securely clamped down. You might ruin what you are doing, or even hurt yourself. At the very least it is annoying.

I cut HDPE with circular saws and mainly treat it as if it was wood. Although I machine it too. Right now I'm using some HDPE as lead screw nuts in my CNC router project. I am going to have to get some Nylon to replace them with I think.
If you are not using the sandwich cooker for its intended purpose any more, Could you just cook it directly on the metal surface or would it stick too much?

I really enjoyed the instructable, and the videos!
Atomic Shrimp (author)  cerberustugowar2 years ago
Yes - well, sort of. If I cook the plastic directly on the nonstick plates, it comes away easily once it's cooled (and the surface finish is generally a bit nicer), but I can only produce one piece per heating/cooling cycle that way.

With the nonstick sheets, it's possible to set up a one-man production line - one batch melting while I'm clamping up the previous one for cooling.
Gregbot2 years ago
Nice! What brand of sandwich cooker is that?
Atomic Shrimp (author)  Gregbot2 years ago
It's 'Cookworks' - not sure how widely available that is, but I bought this one in Argos (a UK high street catalogue store). I reckon almost any flat sandwich toaster ought to work, as it should have the same sort of temperature range (anything hotter would burn the bread - anything cooler would be useless).

I don't use this one for making sandwiches any more, obviously.
Lorddrake2 years ago
so many projects come to mind ...

oh the thinks I can think .. MUH HA HA HA
This is a great idea. Are any noxious fumes released?
Atomic Shrimp (author)  BigBadgers20012 years ago
The process is remarkably fume-free. HDPE just emits a faint, sweetish smell when melted to this temperature.
rimar20002 years ago
Chapeau, Master!