Instructables

How to melt plastic bottles (pet) or other kind of plastics (no plastic bags) and be able to pour it into a mold?


jtobako5 years ago
Chop into small pieces. Heat carefully so it doesn't catch fire-maybe a heat gun on low? Heat up your mold-the plastic will freeze when it touches the mold if it gets a chance. Pour the thick glop of plastic into the mold. What kind of mold are you thinking of using? Without an injector of some kind, it will probably need to be an open-faced mold, or you would have to heat it and let the mold keep melting the glop of plastic (and have a way for the air to escape). What are you thinking of making the mold out of? If you want good detail, the mold is going to have to be heated, leaving out any plastics.
ricehimself (author)  jtobako5 years ago
actually I only have access to wood. the main pourpose is to make a open face mold. probably squared, so that i have a solid block of plastic that I can dremel up by hand. I'm planing on build a camcorder grip. so i'm testing possibilities.
Wood isn't going to be a good choice, it's pourus and the plastic is going to soak into it like glue. You could line the wood with aluminum foil. As for machining plastic, I've had better luck with a knife and other carving tools rather that trying to grind with a dremel-way to much dust.

You might try this unless you just have some plastic laying around that you're trying to repurpose. Different sizes available, easy to use.

http://www.amazon.com/gp/product/B003QKLJKQ/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1

Can anyone help me with my idea, I need to make an oval shaped mould of plastic, the end result needs to be quite a hard finish, and about an inch in thickness, my idea is to have a metal mould, heat the mould up, melt the plastic within the mould then let cool and tip out of the mould, would this be possible,and which would be the best plastic for this?
you can use ABS dissolved in acetone and let the acetone evaporate to form plastic
Thanks, what's abs?

ABS is another type of plastic. You won't really be making it, just reshaping it. LEGO bricks are made from ABS. Many 3D printers use ABS as their source material.

You could use two part polyester resin, available at any auto parts store as well as the home improvement stores. you mix and pour into your mold and once hard you can shape it with your dremmel.
vguerrao1 year ago
I have two drums of white water bottle caps to melt (probably in several batches) to separate the little dirt and reduce their volume to store them easier. I have an electrical plate 10 x 10" with controlled temperature.
-DOUG-2 years ago
You're making a tall order trying to melt down plastic. (Forget heat guns.) It will become liquid napalm, so don't get it on you.

It is possible to mold polystyrene, recycling number 6 and the white EPS foam in packing material and coffee cups, by dipping it in acetone. Wear latex gloves, continued exposure to acetone is a bad thing. Do not use a container made of polystyrene to hold the acetone. You can use a wood mold.

There are mold making projects on Instructables. The most important thing is that the higher the temperature and pressure, the stronger the material must be. Working with melted plastic pretty much requires steel or aluminum molds.

The plastic smithing project, often called plastic morphing in the plastic field, could have its' uses but see how bad the finished project looks? This only works with material that melts below the boiling temperature of water.

There are vacuum forming device projects on Instructables, wood makes an excellent open face mold for it but you have to drill tiny holes at all the deepest parts. You would be using sheets at the forming temperature, which is lower than the melting temperature.

To recycle to get the sheets, you would need to extrude sheets of the plastic. Think of playdoh where you squeeze out the shape through the die. In this case you'd be squeezing out a sheet, perhaps you want a foot wide by .125 inch thick and 2 feet long, you have the foot width and the .125" height opening and push through a 2 foot long piece onto a surface that allows it to lay flat and cool. I haven't found such a device project on Instructables.

There is at least one project to build a roto-molder, your best way to make something you can use, such as a large container. Grind the plastic up to the smallest pieces you can.

There are several projects for an injection molder, but you'll want a metal mold. Successful injection molding is done with a machine the size of your car to make a 6 ounce part, the projects here are overachievers and might not be so rewarding once you build them.

Some of the projects that call themselves injection molding are actually compression molding. You're just squeezing the plastic into shape. Possibly a safer bet when going low tech.

What plastic to use:

PET-E, number 1, is worth money in recycling if you just turn it in. All plastic is recyclable but in California the little coke bottle has a 5 cent deposit that has caused 86% of the PET-E to get recycled. If you take 3 pounds of PET-E bottles to a recycling center that sells recycled PET-E, you can buy 4 pounds of PET-E pellets or flakes for what you get for 3 pounds of food/beverage containers. Your shampoo bottle does not have such a deposit on it so it's not worth as much recycling.

Polypropylene, number 5, is the original tupperware material and still their favorite. Starbucks cups, coroplast signs; this is a material that does well in the sun, does well if it gets hot, does well under duress. Only 3% of California PP is recycled.

High density polyethylene, number 2, is the "Tuff Sfuff" Mattel used to make the toys of that name with. Gallon milk jugs, motor oil bottles, probably your rotomolded plastic trashcans.
KDB9554 years ago
I have been playing with this for a while. I have used only PET or PETE: the ones with the number 1 inside the recycle symbol on the bottom.
The melting point  is around 500f and the crystalization point is slightly higher than that. If you get it to hot it is no longer transparent and turns milky white. Basicly it "curdles" so instead of a nice creamy alfredo sauce you end up with cottage cheese. it is also brittle compaired to the original material. There are a few chemicals mentioned in the wikipedia article that can help it melt at a lower temprature but I have not tried them yet.
crossless4 years ago
 Woah! I will try this someday when I go to countryside so many juice bottles go to trash that it makes sad 'cos you can't yet recycle them all. I think I use as melting heat source our outdoor grill for this one. I was thinking maybe make some food plate for my snails.. I think I could use as mold some aluminium food pan what you get food store those cheap and it don't last many uses and I want to get some edges on it so I could find some smaller pan put it in middle and put some weight on it. Sound fun thought this is not the most ecological thing you could do but less trash till they get some more ideas. Have to start to safe some bottles and some yoghurt cups for this on. :)
 I forgot to say I saw this bolw made of bending lp disk, I would love to make one myself maybe I try some day that too you can get almost them free those disks and "design" bolw cost like 30euros it's about 40dollars. Just the name cost so much..
peterochs4 years ago
I was thinking a um, open-faced mold.. cut plastic into as flat of pieces you can... hover them over the heat source and then press them into the molds - if your release (aluminum foil or whatever - or maybe use some spray adhesive to coat the mold with sand) is good you may be able to heat it and re-press it a couple times to get more details in - if you're able to figure out the temperature/malleability
You might be able to use #5 plastic (PP) in that way. I haven't tried pouring it but I have gotten it melty enough to completely deform and mix colors. PET and HDPE both work better under high pressure forming like injection molding.
NachoMahma5 years ago
. You can't. Most poly-whatevers are extruded/injected/formed at very high pressures. The stuff doesn't pour, it just becomes slightly less viscous.
Yeah, the molten plastic is extremely sticky instead.