I Need information for melting PET plastic at home

I want to melt PET plastic at home. I want to make a clear tube. I know i have to dry the plastic as much as possible to keep it clear. I will dry the plastic by exposing it to a lower temperature than its melting point for few hours. I plan to melt the plastic into a liquid and pour it into a mold. For the mold i will use 2 fire resistant pipes,and pour the plastic in the gap.

Are there any hazards to this,like toxic fumes?

Can i use 2 fire resistant pipes as a mold?

Is there a better way to dry the plastic?

If i forgot to ask something important please answer that too.

thank you for the answers.

sort by: active | newest | oldest
legendarya (author) 4 months ago

Thank you to everyone for your answers. This seems like a very hard task to tackle for me. I have no experience and no tools for this project,other than household items. I also do not have access to an open area to do this outside. But i know much more about it thanks to your answers. For now,i am going to give up on this idea,but i will give it a try when i am in a more suitable position. I will document it as well.

Downunder35m4 months ago

There is only one way to create a clear tube without any air in it - that is by extrusion.
Alternative would be to melt in a vacuum chamber and then to allow to equalise the pressure several times to force air bubble out.
Both will most certainly still end up with more air than what you can tolerate.

PET is not easy to handle.
Even at temperatures high enough to melt it there is little chance of actually mixing it unless you can use great force - like in an extruder.
Next problem is the degradation of the material itself - both from the heat and by contamination/oxidation.

I suggest you do a small scale test to understand the weird and complicated ways PET will act when melting:
Use proper protection and do this prefably outside....
Get some frying oil that can tolerate 280°C - at least for a short time without smoking or catching fire.
Put oil in a small pot and add a smaller pot or stainless steel vessel for plastic.
Use a thermometer to monitor the temperature of the oil, when getting over 200° take great care to get just over 250° and wait until it the temp stabilizes.
Now add your PET into the smaller vessel and try to melt the pieces - it will take a few minutes for them to go soft.
If the plastic stays too hard to melt it together increase the temp slightly to around 265° and keep trying.
I guesstimate that around 270° you might be able to produce something sticky but it will already show degradation and start to go yellow brownish in color.

rickharris4 months ago

PET Melts at 260 deg C.

You will need to dry it at 160 deg C for 4 + hours.

It is VERY unlikely that you will be successful.

1. As you heat it in open air the PET will degrade, It will colour. become more brittle.

2. This isn't how PET is processed commercially - They use pellets, mould them under high pressure.

3. The PET will not flow well even when at it's melting point, much higher and it will degrade.

4. Depending on your application you will be better off buying an acrylic tube ready made, rolling a sheet of PET into a tube, rethinking your plan.

Have you seen clear PVC? It usually has a blue tint to it, so I guess it is not as clear as PMMA (aka acrylic, and other names).

I mean, there is more than one kind of clear, hard plastic.

Although I guess the reason I like clear PVC, is because it comes in the same sizes as regular, white, or gray, PVC pipe, and it can be used with the usual PVC pipe glue and fittings.

g-one rickharris4 months ago

+1

Even if PET is not even the material that are commonly used to produce tubes it would be at least possible with extrusion technology which isn't something you could do at home.

Pouring will not work. The material degrades under influence of oxygen, the molten material is viscous which will cause air inclusions. But the most important reason why it will not work is that the material will shrink during solidifacation. You will never be able to remove the inner pin as long as you use a cylindrical pipe for it. It would need a draft angle of usually ~2°.

More hazardous as fume is the temperature of the melt. Even good gloves wont resist the heat for a longer time. Molten plastic will stick on your gloves as well as on bare skin. Very painful as I can say from own experiences (our company produces blow-molded plastic tubes).

Jack A Lopez4 months ago

PET plastic bottles tend to shrink when heated, and there are a few 'ibles here that exploit that property.

https://www.instructables.com/id/PET-bottle-as-a-h...

https://www.instructables.com/id/Make-This-Bangle-...

The first one I linked to, uses an electric heat gun. The second used a clothes iron.

I am guessing the temperatures needed to make PET bottle plastic shrink are not that high. Probably just a little above the boiling point of water. Guessing 100 to 150 C? This is much less than the actual melting point, quoted in the Wikipedia article for PET

https://en.wikipedia.org/wiki/Polyethylene_terepht...

and much less than those temps mentioned by Downunder35m. Although, he has probably given the best answer here, if you actually want to melt the stuff.

Regarding temperatures around the boiling point of water (circa 100 C) I think I have seen PET bottles warped, distorted, by low temperature steam. There is this sort of parlor trick (or is it party trick?) where a PET bottle with a few milliliters of water is cooked in a microwave oven for several seconds.

There is a possibility of a small, steam explosion doing this demo, especially if the bottle has its cap screwed on, so steam pressure can build inside the bottle. Usually the bottle cap, or the threads under it, is what fails first, and the bottle cap is thrown off explosively.

I guess what I'm saying is that demo will work better with gloves and safety glasses, and you should avoid pointing the cap-end of the bottle at people, or things, you do not want injured.

It melts at 260 C and cools too fast to pour in a mold.

It might work better if you use a vacuum to pull the PET into a hot mold and then let it cool.

Molten plastic is sticky, the thing you will find hard is the right release agent for the molds. Without a release agent in the molds all you will make is a mess.

Chop up the plastic and blow warm dry air through the chips to dry it.

If you want to build an Extruder, a piston extruder is easier to build than a screw extruder.

rickharris4 months ago

I forgot to say yes as you heat it it WILL give off fumes your not going to like much.

Google the safety sheet.

I dont know if there will be fumes, but I would take the precaution anyways. Do it in a well ventilated area.

What kind of pipes do you plan on using? do they have a higher melting point than the PET? Can you heat them up so they dont prematurely cool the mixture?

To dry the plastic, I would imagine a combination of heat, movement and airflow would give the best result. Possibly wash it with something that will remove any dirt, oil and contaminents.

I havent worked with PET before, but I don't know how easy it will be to get it to flow. Would you be able to put your mold together and then melt your plastic in place?

Best of luck and be sure to document it and show everyone how it turns out (even if it doesnt turn out, failing is a part of learning for everyone)