Need help with home plastic smelting

I want to reuse some of the stuff that I've been throwing (bottles, plastic bags, etc) as well as plastic casings (from radios, CRT monitors, etc). Hope to melt/ mold them into usable parts.. What items in the garbage that are best suited for this? Something easy to work with at home / garage (low melting point, doesn't produce that much toxic fume, and the like) Btw, I've tried melting soda bottles, too sticky to work with... Any suggestion, help is greatly appreciated..

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TIKIWOLF3 years ago
ShapeLock low temperture plastic is great for molding stuff:
Take your plastics to Recycle Center.
oldaza3 years ago
move on to electric heating, it will be easier to control heat. you can use any laser infrared to know the temperature of plastic, and somehow control it by turning off the electric stove when it reaches a little below the melting point. Due to thermal inertia, temperature will continue raising a bit, then start to decrease. the container for plastic can have the shape of a syringe, so you can force the plastic out when melted. let me know how it goes
110100101105 years ago
PET (transparent bottles) and very hot water. no fire. it usually gets clean and neat plastic like electronic cases is the worst i think
jeryk5 years ago
try using tongs (like is used in metal casting and raku firing)to handle your container of molten plastic, along with the afore mentioned safety gear. less chance of getting blister packed.
Patrik6 years ago
Instead of actual "smelting" of plastic, you guys may also want to have a look at vacuum forming. Cockpits of fuselages for RC planes would probably be a good fit for this.

Here are some existing instructables on the topic. Note that the first one is a very "home-built" version, using a heat gun, peanut butter jar, vacuum cleaner, and plastic from a milk jug. The other two require a bit more in tools.

How to Make Your Own Prototypes : How to make your own Plastic Vacuum Former
Make a good, cheap, upgradeable sheet plastic vacuum former
Vacuum Former

For those of you more concerned with recycling and less with looks - you may want to give this a try with layered shopping bags. You may be able to get some interesting sheet plastic by stacking enough of those. Dunno - just give it a try...
burgener6 years ago
What is I heat up the plastics inside a sealed chamber with a vacuum applied, or purged and filled with CO2 or other readily avilable gas? Then maybe the chamber could be removed from the heat source, and presureized, thereby "squirting" the liquid plastic into a mold or an extrusion die? Or am I just exposing my ignorance?
Patrik burgener6 years ago
This is pretty much how extrusion and injection molding works. Toxic fumes and high-pressure molten plastic - not necessarily something you want to do at home...
scorpman6 years ago
I was thinking of doing something like this, anyone try anything similar or have tips? I was thinking of making cockpits or fuselages for R/C gliders by using a plastic bottle and shrinking it around a mold. I know I would have to cut it off and glue the seem, but that would be fine. I was thinking of just having the mold on a long rod and dipping it into hot oil. The premise behind this method is a long time ago, my sister use to work at a fast food resterant and they would make keychains from placing the clear plastic lid of the baked potato container into the frier. It would shrink and harden. Think it would work?
NachoMahma6 years ago
. Most of the thermoplastics that you find around the house are not DIY-friendly. They are usually injected or extruded at very high pressures. There's probably something you can do with the stuff, but don't expect to heat a bunch of it on the stove and pour it into molds. . Of course, there are a LOT of different plastics - some may be easier to handle than PET (beverage bottles), PE (garbage bags), PVC (plumbing), etc.
gyromild (author)  NachoMahma6 years ago
don't expect to heat a bunch of it on the stove and pour it into molds.

Thats what i was hoping for actually..
But like you said, there are a lot of different this point i've ruled out PET, yesterday i experimented a bunch of drinking straws, it became charred and end up being brittle (overheated i guess)..

Btw, you reckon PVC will be hard to work with?
> you reckon PVC will be hard to work with? . Probably. And toxic to boot! . . I think drinking straws are made out of PE, which breaks down at high temps. IIRC, we ran our extruders (PE pipe for natural gas service) at ~350 degF. . . If you do find a common plastic that is easy to use, it should make a good Instructable.
Some where I read that burning PVC creates dioxins, and they cause cancer.
Patrik6 years ago
I don't think you'll be able to get around the "stickiness" of molten plastic. Your best bet may be to melt the plaster right in the mold instead. If you start with fairly rigid plastic, you can probably use an old blender to reduce it to small fragments. Pour plastic powder into you mold, put mold in oven... You may want to get yourself one of those nice silicone muffin trays to experiment in. Should be non-stick for most plastics. You'll probably wind up with something that has a lot of air bubbles trapped, but that may not be a problem, depending on what you want to use this for. With good temperature control, you may be able to fuse the plastic particles together without completely melting them. That would make the plastic hold the shape of the mold better - otherwise you might wind up with a puddle of dense plastic at the bottom, and a bunch of bubbles at the top of the mold. You could also try adding various filler materials to the plastic powder, before pouring it into the mold. If you can make the plastic powder fine enough, you may not even need to worry too much about mixing properties of the filler vs plastic - kinda like how high-tech ceramics can made by sintering mixtures of powders. Good luck with your experiments, and let us know what you find out!
gyromild (author) 6 years ago
Thanks for bringing this back up. Since I posted this, I've experimented with several type of plastics, with unsatisfactory results. Namely PET, Polystyrene, Polypropylene. The main problem is when you melt plastics, they will first reach a glass state (a blob). In this state, they are sticky and extremely hard to work with. Let alone pour into a mold. Yet when cooled, they harden into somewhat strong plastics, but tend to break when I forcefully try to bend them. Further heating will cause them to melt fully. Not sticky, and easily poured into mold. However, heating beyond the glass state also degrades the quality of the plastic. They cooled into hard plastics with polished surfaces, but shatter when dropped. I've read that in the industries, they use plastic stabilizer to enable plastics to be molten fully without heat degradation. One of the main component of the stabilizer is fluoride. Haven't tried that though. I'm not much of a chemist, and the only source of fluoride I could think of is toothpaste :P Btw, adding a tiny amount of soldering flux helps in preventing the molten plastic from getting burned or charred. And I didn't noticed any difference in form (visibly at least) and strength when they harden. But again, I'm no chemist. Thanks
Lextone6 years ago
Best way to melt plastic to a viscus state is by indirect even heating...basically a double boiler but with oil in place of water. Take one pan and fill it halfway with cooking oil. Then place a smaller pan inside that one with your plastic bits. Then fire up the stove and bring the oil up to a temperature of about 350-400 degrees F. The plastic will melt without burning with minimal fumes. REMEMBER- Wear appropriate safety gear. I recommend a face shield leather boots and welders gauntlets. Oil gets very hot and is a fire hazard. Turn off all flames before removing your plastic melting pot to avoid flare ups. Have an appropriate fire extinguisher nearby. DO NOT USE WATER ON A COOKING OIL FIRE!!!!!!!!!!!!!!!!!!!!!!!!!!
Mr_Equinox6 years ago
Okay well some have said it already, plastic melting is toxic, so yer not helping the air much or yourself. But, if you want to still do it? DO IT OUTSIDE!!! Use a grill and wear a mask, better yet stay a distance away while being able to see it. 1st- Ignite the grill or start a fire with Charcoal depending on your preference. 2nd- When it gets hot enough, put a black pan on it or Cast iron one if you can. 3rd- Start dropping only a few pieces at a time to get it started (again) trying to avoid the fumes. 4th- When they start melting into a goo, feel free to lower the flame making it simmer and melt things until your hearts content. Depending on the type of plastic, could happen fast or it can take up to 30 minutes or so to start melting. So this involves patience and watching, if you start to burn the plastic seeing a lot of black smoke your fire is way to hot! You only want to see a little bit of Black Smoke, this is the stuff you definitely do not want to inhale! When all done melting what you want, use some hardcore oven mits. remove the pan and pour into the mold you want to make. Have fun melting away! Try not to pollute to much!
lemonie6 years ago
Slow cooking and exclude air.
An oven might be a good idea as you have temperature control, and can avoid hot-spots.

jtobako6 years ago
You may want to look into solvents instead (or in addition to) heat. Polymer clay (sculpy, fimo, ect) are powdered pvc with a solvent/adhesive added. The solvent will evaporate at room temp (takes about a year...), but the pvc ends up fused if you use heat.
Bran6 years ago
Saran (sp?) wrap could possibly be made into something (seen here), of course I don't know what you are planning to make out of the plastic. I believe most plastics produce carcinogenic fumes, but I couldn't tell you which produces the least. One time, just for fun, I took a match to a Crayola Marker cap, it melted pretty easy. I can't quite tell you how strong it was.

I have a few questions, if you don't mind. What are you making out of the plastic; how are you heating the plastic up to melting point; and what are you using as a mold (if anything)?

Anyway, this sounds really cool, and I think if you get any result out of it, you should make an Instructable on it. Good luck!
gyromild (author)  Bran6 years ago
The idea is to explore options in creating small plastic parts from common everyday plastics. Poor man's plastic molding. I use a gas stove to melt them..i have an oven, but i'm not really comfortable with the idea of having toxic residue left in the same thing that i use to prepare food.. As for the mold, i use plaster of paris..since i'm still experimenting.. I will give the marker cap a try, thanks for tip..

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