Casting PVC

[Pilgrimman]

Well, the question is in the title. Is it possible (read: practical) to melt pvc and cast it? If so, is there any cooling problems, etc.? I don't know much about casting or molding, but I have access to plenty of PVC. Help is appreciated!

[FordGtMan]

I have never been able to melt pvc, it just seems like it gets pliable then starts to burn. But that was with a torch so there are other more accurate ways, but i dont think you can.

[Eddbot]

there is one way to find out...

[sandman]

cause we all want to risk heating it enough to release chlorine gas

[Eddbot]

would polly-vinyl be a suitable material for pipe?

[Pilgrimman]

As for the melting bit, I would melt it with hot water, or an oven, and ALWAYS wear a gas mask. I thought the mask was implied, but you never know who would try it without...

[jackssmirkingrevenge]

*cough*epoxy*cough*

[Pilgrimman]

Yeah, I'm surprised I made 2 posts before I heard that... I was never really good with epoxy, though. I was asking the question more to see if it was practical or had been done. I'll agree, though, epoxy is amazing stuff! (Until you get it somewhere it shouldn't be)

[jackssmirkingrevenge]

I'll agree, though, epoxy is amazing stuff! (Until you get it somewhere it shouldn't be)

Casting in general is bound to be a messy business if you're not careful, so I think it's more down to technique than materials...

[Pilgrimman]

...Yeah, my skills are lacking... I'm just trying to give the skilled people's brains a little kick-start

[Matheusilla]

If you're making a piston, maybe shopping bags could work (I think they are polyethylene). Some plastics can be melted and re-formed/cast and others can't. The temperature used is higher than boiling water but not too high or the plastic will start to smoke. You would need a mold of some metal and be able to compress the melted plastic inside. At this point it would probably be better to hire a machinist to make the part.

[jackssmirkingrevenge]

The only real objection I have to epoxy resin as a casting material is the amount of time it takes to cure, and how that time is very sensitive to ambient temperature. Other than that it flows very easily, sets rock solid and requires no heating or similar complications to mix - plus you can mix it with virtually anything from sand to talcum powder to strands of wire to give it more volume or strength.

As long as you've got a watertight mould that's thought out properly, there's no reason why it shouldn't go well.

[Spuddin]

ive melted it in hot oil enough to force it into a round mold to make a pvc plug to fit inside a pipe. it worked ok but had wrinkles but after cementing it in it sealed to my satisfaction. never been able to completely melt it but if u ever melt something that light u really need to add force when pouring to get it to flow and fill the voids like they do in pressure casting. it would be great to find pre mixed pvc.

[psycix]

I once had the idea in my head of melting PVC in a vacuum or Helium (or any other non-reactive gas, nitrogen may work too) environment.
It can melt, but it cant burn that way.
The only problem I can think of is that it may release its chlorine gas and thus your PVC becomes PV.....

And ofcourse its not very easy to cast it that way. You will need to fill your mold with pvc schrapnel (and some on top of it), close it in the oxygen-less environment and then heat it.
This would be like, putting the mold in some sort of jar, sealing the jar of after taking out all oxygen, and then putting the jar in the oven.

[rp181]

When will people look at wikipedia?

It says it melts at 80 degrees celcius, so in boiling water. It seems when people "soften" it, it really melts. PVC is probably just really viscous, as it also has a really high density.