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wierdscience
03-23-2013, 11:21 PM
Anybody here have experience with weldable PTFE aka NXT Teflon?

I have some seals to make,the OEM seals are 6" square and made from 1/8" thick 1/2" wide strips welded at the corners.

I can make these by simply cutting them from solid 1/8" thick PTFE sheet,but the waste starts to pile up and at $30/sf it's not exactly cheap.

I'm assuming the NXT is welded using hot air,what would the learning curve be like and what are the draw backs if any to the process?

If I could manage it I would cut 6x6" L shapes out of sheet and then join the opposite corners to form the square.

Evan
03-24-2013, 02:25 AM
PTFE is actually a thermoplastic although it does not behave like one. It is possible to heat join it if it is heated to around 621F or so. It begins to degrade not far above that temperature which is very toxic so it is important to heat it accurately. There is PTFE welding equipment available for regular PTFE. It does not flow when it melts. It forms a so called "gel state" which is nearly the same as the unmelted state but it will heat fuse.

I have not tried it because of the inherent hazard.

wierdscience
03-24-2013, 09:15 AM
Okay,so with a fume extractor and some fine control it should be possible to join common PTFE?

This has me thinking of retrofitting a 150 watt soldering iron with a stainless steel spade tip and a termocouple readout.Then using a Variac to control the temperature of the rig and seeing what happens.

I have to figure out something,cutting them from solid will leave me with $300 worth of scrap.:(

Evan
03-24-2013, 01:08 PM
I will be very interested to hear what you find. Take great care with the fumes and wash your hands well after handling heated material. It would be a good idea to wash the finished product as well. I also suspect that it is a good way to get burns as the heated PTFE will cool very slowly. It is a very poor heat conductor.

lakeside53
03-24-2013, 01:13 PM
Unless you are trying to spot tack, I think you'll do better with a hot air welder. I have a fairly high end unit, but find it's is difficult to get everything stabilized to an "exact" temperature. You need to control the air flow and the element, and wait for it to stabilize. It's also not like welding metal -there is no "puddle", heat flows though the material slowly so you need to keep it moving over a larger area then you may think, and it's really easy to "char" some plastics.

On the other hand... I have a Bosch heat gun that has digital control for temperature (100 to 1200F) and has adjustable air flow. I've often though it would be better to make nozzles for that.

I haven't tried PTFE, but I have done quite a bit of glass filled nylon (difficult to do well) and some on pvc (easy).