Melting PVC

[SEAKING9006]

.... Well, sh!t.


The I guess we'll change the focus of the thread towards finding a thermoplastic material that is widely available that can be melted fairly easily.

[jonnyboy]

He never said it was it was just possible. I saw instructions on melting plastic bags somewhere.

[SEAKING9006]

I know, but the possibility of toxicity wasn't the only problem. Plastic bags were the second thing on my list to try, with those also being made from thermoplastics.

[jonnyboy]

Heres a link of plastic bag molding looks like the fumes are toxic though so don't do this inside. http://www.instructables.com/id/Plastic ... cery-bags/. The finished results don't look that good but the guy just lit the bag on fire as opposed to heating it.

[jimmy101]

.... Well, sh!t.

The I guess we'll change the focus of the thread towards finding a thermoplastic material that is widely available that can be melted fairly easily.

Hey, don't give up so easy. It would be very handy to have a way to cast PVC (Type 1 Grade 1).

I wonder, how are PVC pipe and fittings made at the factory? Is it formed as a thermoplastic or do they do the polymerization process in forms?

A little more research might come up with a way to get this to work without having to worry too much about off-ing yourself.

[jonnyboy]

I knew the instructable was around here somewhere!

http://www.instructables.com/id/Starch_Plastic_20/
http://www.instructables.com/id/Make-Potato-Plastic!/

This was the one I was looking for last night. Less glycerin makes it harder less makes it more flexible.

[cocodoc]

jimmy101
Read your post on PVC from 09/08. It seems you know a lot about PVC, maybe you can help me. I'm trying to heat 6" PVC pipes enough to reform them and hopefully it will retain that shape when it cools. Do you think putting it in a boiling water bath would accomplish this? Also is there any chance of toxic fumes?

Thanx, MAK (cocodoc)

[john bunsenburner]

Well PVC being y hydro carbon and having chlorine in it is prone to give of HCL, tear gas, and essentially hydro chloric acid when heated/burnt. I assume there is a big risk of that happenign and I recomend trying grocery bags, however they need to be pressed into a mold hard and melted in cooking oil. Overall i suggest using plastic stock in the right diameter and to then file that if you want a single object...Casting is inconsistent and dangerous...

[USGF]

Well PVC being y hydro carbon and having chlorine in it is prone to give of HCL, tear gas, and essentially hydro chloric acid when heated/burnt. I assume there is a big risk of that happenign and I recomend trying grocery bags, however they need to be pressed into a mold hard and melted in cooking oil. Overall i suggest using plastic stock in the right diameter and to then file that if you want a single object...Casting is inconsistent and dangerous...

John, You need not heat it to have the smell. We machine lots of PVC for various customers. The smell turning or milling generates is really bad. Will make you sick in a few hours. I have a large dust/fume collector on one of the mills. We tried laser cutting PVC once. A big mistake. In the same way you can cold form lead, we are considering heating PVC till it is "plastic" and then placing in a die set for pressure forming.

USGF

[Biopyro]

Nope, no significant fumes from softening PVC in water (70*C is plenty), and it will keep it's shape when cooled.

[jonnyboy]

You need not heat it to have the smell. We machine lots of PVC for various customers. The smell turning or milling generates is really bad.

It's the friction generating heat.

[SEAKING9006]

Hey, sorry I didn't post after I did it, but I got a half-decent result after burning around 10 bags into the bottom of a soda can. Gave me a neat little dome. But it was pretty brittle, and full of air bubbles.


Now as far as softening PVC, it's perfectly safe. When I work on my schools robotics team, I use an electric heat gun and a toaster oven to heat the PVC. It gets nice and pliable. You have to hold it until it firms up, but that's usually not an issue. At home I've got a pneumatic 'plastic welding kit' that has an electric blower fed from a 1/4in air line, and it works well until my compressor tank runs out of air... Anyway, the trick is to not hold it still too long or the plastic will burn. Do it right and it's hella useful, like for making sheets of PVC.

[Technician1002]

There are newer threads on this subject with photos. Check these.
http://www.spudfiles.com/forums/reformi ... 18417.html
http://www.spudfiles.com/forums/general ... 18336.html

The threads include bending PVC into 180 degree U shape and putting bells on the end of 6 inch PVC pipe.

[kenbo0422]

Jimmy101-

POLYvinyl chloride indicates the monomer has already been polymerized. The monomer is an acrylate/acrylic acid/urea type of monomer, or possibly of some other base chemistry, and is exothermic during the polymerization process.

I used to run the reactors for making that stuff. Very interesting process.

[jimmy101]

Jimmy101-

POLYvinyl chloride indicates the monomer has already been polymerized. The monomer is an acrylate/acrylic acid/urea type of monomer, or possibly of some other base chemistry, and is exothermic during the polymerization process.

I used to run the reactors for making that stuff. Very interesting process.

Uh ya, so?

Yes it is polymerized, which is why it is amorphous and why it doesn't have a true melting point. Vinyl chloride is a gas at room temperature.

It is not an acrylate/acrylic acid/urea type, though there may be small amounts of other polymerizable materials in the mix to change the characteristics of the final plastic.

Vinyl chloride is pretty toxic. PVC is not. No polymerization process is perfect, there is generally some monomer left over.

Polymerization releases heat and does not involve the loss of any atoms from the monomer. That generally means the process can be reversed by heating (which is an example of Le Chatelier's principle.) Get PVC hot enough and it will start to release vinyl chloride gas.