Will PTFE shrink when heated?

Re: Will PTFE shrink when heated?

Tue, 29 Jun 2010 19:25:20 +0000

I used a hacksaw with a very fine blade, and then had to clean them up briefly with an x-acto. One melted PTFE will make you a ton of washers.

Re-use!

Re: Will PTFE shrink when heated?

Tue, 29 Jun 2010 16:49:49 +0000

Indeed, indeed. Just need to figure out how to cut it…

Re: Will PTFE shrink when heated?

Tue, 29 Jun 2010 15:24:26 +0000

Sounds like you have potential PTFE Washer Slices now…

Re: Will PTFE shrink when heated?

Tue, 29 Jun 2010 14:00:28 +0000

For future reference, when I tried this I didn't know, and thus failed to take into account, that PTFE apparently has no shape memory. Toasting it does make it wonderfully flexible, though.

Going to see about ordering a PEEK insulator or two, maybe even a hybrid, and the PTFE that was used for this exercise will hopefully become washers.

As for the question I had about fumes: the maximum temperature of this toaster oven is 450F. I don't know if that's true of all toaster ovens, but in any case it seems to be a safe temperature for working with PTFE, as my reading indicates that it doesn't start giving off fumes until 500F (260C), and it shouldn't cause Teflon flu until it hits 662F (350C). And I'm still not sick or dead yet, so there's that too.

Overall, though, I don't know how useful doing this would be - if at all.

Re: Will PTFE shrink when heated?

Tue, 29 Jun 2010 01:51:53 +0000

Yes, the nut should be ABOVE the big washer. Once you nuke a PTFE you can use slices of it as washers between the nut and the big washer, to help insulate it.

Re: Will PTFE shrink when heated?

Tue, 29 Jun 2010 00:12:56 +0000

Are you asking how it should be done or are you trying to find out how his is set up? If you're asking how it should be done… I went with a nozzle, barrel, washer, nut, PTFE stackup.

I think the purpose of the nut is to keep the the filament from pushing the barrel out of the PTFE. Once it gets hot, the threads in the PTFE will strip out much easier. The nut is more capable of transferring the filament load down to the washer, which in turn transfers it to the retainer ring.

If you switch the washer and nut, the nut will be trying to pull the barrel out of the PTFE (especially if you make it wrenched-on tight, finger tight might not apply enough force to be noticeable). Once you start extruding, the nut can't transfer filament load to the washer.

Re: Will PTFE shrink when heated?

Mon, 28 Jun 2010 23:27:37 +0000

Oh frack! I'm adding a hose clamp to mine tonight!

Uhm…
M16 Nut BETWEEN the PTFE and the Washer (Nozel, Barrel, Washer, Nut, PTFE)?
or in front of Washer? (Nozel, Barrel, Nut, Washer, PTFE)?

Re: Will PTFE shrink when heated?

Mon, 28 Jun 2010 20:59:20 +0000

alas; it leaked again

Re: Will PTFE shrink when heated?

Mon, 28 Jun 2010 19:06:41 +0000

Sadly, we don't have any hose clamps, but we're hoping to rectify that soon.

Well, I went ahead and toasted it - 450F for 20 minutes. The results are as follows:

I'm not dead. Yet.
The PTFE did not magically shrink to its original configuration, but it did become malleable enough that it could be squished down to something like it. I squished it down to the point that it fits securely with the metal barrel, and am leaving it in the pliers until it cools.

I'll update later on how well it prints, whether it immediately bloats again, etc.

Re: Will PTFE shrink when heated?

Mon, 28 Jun 2010 18:52:10 +0000

dataman -

hose clamp will help stop the bloat and does indeed act as a heat sink like clothbot mentioned.

http://www.flickr.com/photos/botbuilder/4591058367/

copper plumbing part works well too, even without a clamp:

http://www.flickr.com/photos/jabella/4612505571/in/set-72157623829152993/

Re: Will PTFE shrink when heated?

Mon, 28 Jun 2010 18:45:04 +0000

The pipe clamp does double-duty as bloat-preventer and as a heat-sink for the PTFE plastic.

Re: Will PTFE shrink when heated?

Mon, 28 Jun 2010 18:37:34 +0000

We just got out plastistruder working from our initial build. Not sure if it's related, but turns out we were suffering from a constipated PTFE. Had to bore it out with a 1/8" drill bit. I've seen that some people are using a pipe clamp around the base near the washer. Perhaps that's to stop the bloat?

Will PTFE shrink when heated?

Mon, 28 Jun 2010 17:59:43 +0000

We've had problems with our PTFE insulators swelling and allowing ABS to leak out. We are considering using a toaster oven to try and "bake" them back down to their original size.

Will this work at all? More importantly, are we putting ourselves at risk for hazardous fumes? I've read that heating PTFE to 350C or above can cause polymer fume fever.