Plastic Smithing: How To Make your own HDPE Plastic Anything (DIY plastic lumber)

How to make really good hard plastic while reusing and recycling plastic bags at home! Via this method, you can make ANYTHING you want to, out of hard, lightweight, real plastic that's astoundingly durable. It comes out very similar in texture to recycled plastic lumber.

best of all, this method involves no fumes!

I'm gonna show you how to make plastic wheels for your robot!

I first heard about stewing plastic bags to make new things from Dave Huebsch's book " Village Assignment " about interesting adventures had while running a charity/NGO (" Common Hope ") in Guatemala. He, amazingly, repaired the bottom weight-carrying main bearing of a washing machine with a big plastic disc made of stewed plastic bags, which actually was such a good stand-in replacement that it held up for several years. (and here are some more Guatemalan Handy Tricks)

I had to try it right away, and the first couple times I just burnt plastic, until I came up with this method.

By the end of this, you'll be able to make yourself a knife sheath, mold around your shoes and make DIY hard-toe sneakers, wheels, bearings, bushings, or any kind of plastic part! Take pictures and post them in the comments!

Step 1 Materials

Collect all the plastic bags you can get, they shrink down a lot.
Shredding them will make your final texture finer.

Use an old pot that you aren't going to use for food any more, or get one secondhand for really cheap at a thrift store.

Find a stick or something else you can use for a spatula.

I liked the clothespin a lot because I could pick things up as well as stir.

Oh, and oil! (I used canola because it was right there next to my stove. If you're, for example, making a bearing you can impregnate it with your personal favorite grease.)

So grab your favorite oil, here's why:

Plastic bags are made of LDPE (low density polyethylene) which melts at 248 F.

I got the temperature wrong and tried doing this in a homemade double boiler filled with water (to regulate the temperature to water's boiling point), which, of course, just made hot plastic bags.

After the double-boiler mistake I re-read the LDPE melt-point and discovered my folly! So I came up with melting them in oil.

Cooking oil boils around 350, which is far too hot for plastic, and which you don't want anyway (splashing boiling oil = no fun unless you're a hun), so I keep it to a nice low-viscosity canola oil heat and things work just fine.

If you wanted a smooth, non-oily finished surface, consider using wax instead.

ALSO: oil is not required per se --
if you had a constant temperature hot surface that you could guarantee to keep down around the melting point, you could do this just fine with no oil or wax!

Comments

[blackslax]

How about using butter?
Butter has a smoke point of 350F; would probably make a pretty good heating medium; is readily available...besides making the plastic quite delicious.

[greenminded]

I entered a winning idea which is similar to the discussion here. See idea posted entry number 4 : by Mary Jean Netario Cruz 

http://hapinoy.com/12finalist.html

Blocks of Hope

"Plastic Pollution is one of the major reasons of the last years “Ondoy” disaster that put Metro Manila under a devastating flood. In spite of this horrible experience it has been noticed that drainage and floodways continued to be clogged by plastics. An enterprising solution must have to be achieved to recycle and make money out of this garbage. These plastics can be made into blocks where in it can be used to build a shelter. Other use is it can be made into furniture, just like how lego works. An electric block machine has to be designed, either for every home use or for cooperative to process the used plastic into a block. Each block will be sold to the one who build the house or create the furniture using the blocks as one of its major materials. These manufacturers or engineers will design a system where all they have to do is to be like a kiddo playing creation from lego toys. These blocks will be mainly to be used as walls, tables chairs or depending on the block per part design basis. This will solve problems of the plastics and generate income for the household."

Can anyone help me on technical side for my business plan preparation?  Deadline is on Jan 29, 2011.  For those who can help me, please email me at [e-mail]

[nex incendia]

Well plastic could be used as an aggregate filler in cement ;and can be shredded, melted down and custom molded for decorative moulding and mill work and other architectural uses . i understand that you want to use it as a major material in construction and you are right to think so. it is strong and reliable and some types of plastics will not breakdown for a very very very long time. my self being a construction worker and occasional tinkerer of sorts i think plastics is a viable construction material worth exploiting.

[Viaticus]

If bags melt at 250, why not melt them in an oven instead of in oil?

[senica]

After I take the plastic and oil mixture off the burner, do you think it would be okay to add acetone to break down the plastic further into a liquid? I think I read that LPDE (plastic bags) is soluble after 115 F. So I was thinking that while it is still hot, I could add acetone to break it down into a liquid.

But this also seems dangerous as acetone is extremely flammable.

Any thoughts?! I'd try it, but my wife would kill me if I burned down our kitchen.

[stasterisk]

Definitely sounds hazardous, and I have no idea what would happen -- but I'd love to hear how it goes if you try it!

stay safe!

[sdavies]

This is so cool! Thanks for posting this instructable!

[wakojako]

If you dissolve styrofoam peanuts in accetone you can get very similar results to this.

[noctisguy]

Wouldn't that be napalm? lol

[wakojako]

You could use it like that but if you try to squeeze as much acetone out as posible and then let it dry in a mould.

[imagigadgets]

If you used plastic bottles that were clear, could you forge something clear?
I ask because I'm looking for a cheap substitute for Plexiglass, mostly for its... clarity.

[plzspoilme25]

(removed by author or community request)

[plzspoilme25]

okay ive searched all the ppl listed above for molding and casting ideas, i still can't find what i need. i'm wanting to try this to make my seed flats to germanate my seeds the flats i'm using are the 20 row variety, they are not very expensive...around 3 bucks each, but they are not easy to get ahold of shipping cost a fortune for them at seed starting supply sites, and the most local place here is 2 hours away....besides i want to reuse the plastic bags i have....and try this out, my problem is coming up with some sort of mold to be able to pour this mixture into...i do like the idea of the wax added since i last read this. for those not familar with seed flats this is "i think" a 11"x13" plastic tray with 20 separate groves in it for dividing up seeds. i'd like for mine to be a bit shorter perhaps to fit on the shelf system i have for my indoor 'germination station' this seems like a good process to try out except for i need the mold for it....heck y not go ahead and make all my own cell packs while i'm at it....flower pots too....and yes maybe even the plastic lumber (as already mentioned) for my raised garden beds...ANY ideas? i already watched every video and read all the articles here on subject....still not sure what i've found will work for me...i'm gonna try one casting method but think its too complex for me to do......all in all the outer lining of the ones i got aren't very thick or strong, as most cell pack arent either, so i just need something very thin....obviously the original trays and cell packs are injection molds, but i know there has to be a way of doing this....pic is from stock photo at mail order company, the item i need is the front tray, but while i'm at it i can try the other types as well TNX in advance for any ideas...

[Marlock1]

For the grooved one, you could glue dowels onto a flat surface and cover it with the melted plastic.
You could set another board on top as it cools, to make a flat bottom when it has cooled.

For the tubs, glue those small pudding containers to a clear (plexiglass) sheet and use a jigsaw to remove the clear material above each tub.
... glue the plastic rings from a six pack of cola to the tubs?

[zfolwick]

I'm thinking about trying some clay that I have on hand. It cost about $10 for a LOT of clay. about 20 lbs worth it feels like.

[Rogue Gourmet]

plzspoilme25, you could try filling your containers (as shown above) with plaster or paris - right to the top - and add a layer or two of burlap soaked in plaster for strength. When the plaster has set well - remove the plaster and you have a press mold. After adding a mold release agent (like Pam) liberally into your mold press the softened plastic material into the plaster mold, let it cool and you should be good to go with this. It might take several tries to get this where you want it to be, and your final product will not be as thin - but I bet this process will work for you.

[plzspoilme25]

Thanks for your idea, i guess originally i didnt want to use the tray to put plaster of paris in actully i couldnt cause it had seedlings in it at the time, any way, besides that i didnt know if it the tray would "hold" the plaster of pairs, but i got a new idea for that problem using tape....and i wasnt sure if the plastic tray would seperate from the plaster of paris when it dried. like i said i didnt have the tray available at the time but needed more trays.....now i'll be starting with empty trays again so may be able to make this work.....

NEW Question, does the plaster of paris hold up to the hot plastic being pored on it? any other ideas is so, or other ideas to use besides the melted plastic as i' havent had a lot of luck doing that process.btw this is something i'm wanting to mass produce to use in various types of packs and planting trays, i'd like to get good enough that my packs can hold plants that could be carried and sold at farmers market in the future. THANKS

[xenobiologista]

I don't have any experience moulding or casting but I do know that plaster of Paris is made of minerals so most likely it won't melt or anything. The only thing you have to worry about is dropping and breaking it. http://en.wikipedia.org/wiki/Plaster_of_paris

[Silver X Viper]

YO If im right you said you have something like whats in the picture but the plastic is too thin or something... well just take that and get something that it will fit in that is idealy plastic or metal or glass, and if its cookware be sure you dont need it anymore. put it into the container upside down tape the sides so its plastic-tight (LOL) and make sure any other holes are covered with tape and then just pour in the liquified plastic bags... voila! Your own mass seed starter from bags. Oh and do use duct tape or you run a decent risk of melting it otherwise or even better GORILLA TAPE. Last at your discresion you may wish to tape the entire bottom of the seed starter thing if youre pretty sure it will melt otherwise dont bother.

[zfolwick]

I tried this a couple weeks ago using water and covering it with a lid. I turned the stove on high. When I took the lid off to see how it was doing, it burst into flames. I then poured it onto an old cutting board I had and tried to flatten it the best I could. When I was done I had a lumpy mess on my hands. After it dried it was SUPER hard and seemed very, VERY strong for what it was. Tonight I tried the same thing with crisco and a little better preparation. I flattened the goop to about 1/4 inch thick (it didn't burst into flames this time!) and let it air-dry. I then washed the residue off with dishwasher soap and cut a rectangle out. It seemed much less brittle than the water-melted version. I could bend and twist it easily. also cutting it with my hacksaw gave feathered edges. I will probably heat the rectangle plate up on the stove (in water) and stick it in my freezer to see if I can still get the nice hard material I had before. I would like to make an oil-based blank and then finish the mold using water immersion.

[lpkid1057]

I just melted two bags using a double boiler method tonight. The first pot was lined with vegetable oil, the second was a Pyrex glass with enough vegetable to cover the bags. One bag was shredded into fine pieces and the other was just folded up and added once the oil was sufficiently hot. (Not using oil as a medium didn't work. I was forced to cover the bags with oil to get them to melt. The layer of bag touching the Pyrex melted and stuck to it like bubble gum while the rest just remained at room-temp)

both bags became viscous and fused together after pressing (read: mashing) them together with a fork. I removed the mash and allowed it to freeze.

Heres the question. The vegetable oil cooled into a whitish petroleum jelly-like substance. What is it? did the bags decompose somewhat? some polyethylene strands dissolved into the oil enough to turn it almost solid? I don't believe there are any plasticizers or fillers in the plastic bags, just spun / woven polyethylene. Any Ideas?

[Endif]

It makes me wonder if this would make harvesting/mining the Texas-sized garbage patch in the Pacific for materials a cost-effective business model..

[studer.steven]

I have been trying to make a full plain to do just that for a few years. There are some interesting ways to so it if you include the cell phone recycles systems also.

[Endif]

So one could use any oil? What about used motor oil? And does the plastic soak up/bond with any of the oil, or does it simply remain in the pot for re-use? In a scenario where this technique would be most valuable (post-modern-civilization), food-grade oils will be far too valuable to waste on something like this. I guess one could use oil that has gone rancid...

[PlayPatterns]

this was such a cool idea, I tried it myself! Thinking to make childrens' blocks, but need them to come out a little less fugly first....also would this be safe for children? All kindsa toys are made out of #2 plastic anyway....the full build details are at my site, Push The Other Button.

[twotowner]

I decided to try the plastic melting yesterday. I had the opportunity to try it using wax instead of oil because that is what I had on hand. (Wife had a paraffin wax therapy unit she hasn't used in years) I started out trying a double boiler method. But even after getting the wax up over 300F on my candy thermometer, the plastic bag I was testing really wasn't melting much and the milk jug plastic not at all. (I wanted to try the jug plastic because it seemed tougher) I eventually gave up and put the jugs directly into the wax. This worked quite well. I was a bit concerned that the heat had to be up close to 320F on my thermometer to get close to workable plastic. It made me wonder if the thermometer could be in error. With a lot of stirring, I managed a reasonably consistent plastic mass. Scooping it out into the pot I was using for a mold was a little hard. I've got to find a decent utensil for that part that wont hurt the non stick pan and stand up to the high heat. I think the end result of the pour was pretty good.  One thing I would correct the next time I do this would be to thoroughly wash the milk jugs. While I didn't encounter any fumes from the plastic getting too hot, the smell of bits of dried, rancid and then burned chocolate milk is another matter altogether! :p

[nax]

I wonder if the oil/wax serving as a heat transfer medium is the critical factor?

That would also account for the melting without burning: the plastic is heated more evenly. Without the oil/wax, most of the plastic is not getting hot, but the tiny part in contact with the pan is real hot and burns.

I was also wondering about using an electric frying pan or something along those lines.

[zascecs]

Another way to use up old shopping bags... 

[kalo02]

I just made a small trial batch of the plastic before I endeavor on making a casing for a small solar powered fan unit and it turned out great! I was considering using the duoble boiler method to prevent this oily residue, however, I did it the way you suggested and it was fine! the only negative was that it began to melt a plastic mould i had made so i think a plaster mould would be ideal. but this is a great instructable, thanks :) 

[KDB955]

What little I know of polymers suggests that slower cooling will give you longer molecules and a stronger plastic.

If stregnth is an issue I would just turn the heat down a little bit at a time until it was "set up and solid.
Again, this is a slightly educated guess; It might not matter at all.

[jimmy dean]

Was it easy to remove from the mold? Or should I consider greasing up the mold before I put in the plastic?

[spectre03cobra]

  Wonder if you could use propylene glycol (coolant) instead of oil.  The boiling point of 100% PG is ~370 degrees F.

[urbanwoodswalker]

"DIY hard-toe sneakers"....?

I sure would love a tutorial on this plastic utilized in that way. Please share!

[przemek]

I don't think putting hot plastic in the freezer is a good idea---you adding so much heat that you could raise the temperature of other items beyond thawing. We have a rule in my house that things hot to touch never get into the fridge.

[urbanwoodswalker]

Yeah...might be better to sink into a big tray of ice water on the table instead.

[tenpcrisps]

so it didnt melt the plastic container? you just put it in there and it was fine?

[urbanwoodswalker]

I am wondering this too. Should the plastic "mold" be ice cold or coated with more oil as a release agent?

[guatsamosa]

just wondering how hot the plastic is when you can mold it and about how long it stays like that... very cool instructable btw! me gusta.

[sharlston]

is there any way to get rid of the oily texture? i want my finished product to be smooth

[Lokisgodhi]

The way to do this is to make a rough casting of the object you want and then machine it to the shape you want.