Overcoming heat problems on the hotend, suggestions?

I created a new and slim nozzle from aluminium with a direct heating system instead of heater cartridge or big resistor.
Heat up to 200° in a few seconds, very easy to push filament through by hand (0.7mm nozzle).
However the actual use in the printer troubles me a bit.
Using a stainless steel heat barrier and a teflon mount to the x-carriage the printing is really good - until I stop or restart.
Once stopped the filament inside the steel tube swells up and blocks it so you need insane amounts of force to push it through.
I know using a long steel tube with a heatsink and fan would be the perfect solution by this is next to impossible with my x-carrier.
PEEK is next to impossible to get for a good prince down here so I was wondering:

With a direct, screw in connection, the heat from the nozzle will be transfered directly into the stainless steel.
Using a teflon liner is no solution as I want to be able to print nylon as well.
But what if, instead of heatsinks and fans, a relatively thin PEEK connection is used between nozzle and heat break?
I would prefer some ceramic though but have no acces to a proper kiln.
My theory is to produce a complete heat barrier between nozzle and rest of the hotend.
Would PEEK by still strong enough at higher temps so a screw connection won't rip apart from the filament pushing down?

A picture is worth a thousand words.

How thin would you make the PEEK? It is not nearly as stable as steel and it does get softer when heated.
Btw, every hotend makes it easy to push filament through a 0.7mm nozzle, try 0.3 to see if it is realy any good.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

I have some pics and videos included in my Instructable.
I was thinking of using a 5mm thick PEEK "washer" with a 8mm thread for the nozzle and a 6mm thread on the other side for the heat barrier.
Here is a pic of the hotend in comparison to a standard J-head.

And here just the nozzle ready to get the wires attached.


I have no dramas printing PLA but the main goal for this design was to be able to print Nylon and other high temp plastics as well.
And if PEEK is not up to the task I will have to go ceramic for the connection between nozzle and heat barrier.

I print Nylon and other Materials with up to 260°C with my PEEK based Merlin. I use 10mm diameter though.
If you take a look at the Merlin it does rely on threaded connections on the in- and outside, so yes PEEK can be used that way.

[merlin-hotend.de]

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

Thank you for that!
Will have to source some PEEK rods now I guess .
Found an even better plastic for the job, Vespel - a high temp engeneering plasitc with superior properties.
There is a few downsides though: Availability and price.
If you though PEEK can be expensive to get check the only Ebay link for Vespel I could find and have a good laugh: Vespel SP1 - Ebay link.

Ordered a few 0.3 and 0.4mm brass nozzles and will do a new design based on replacable tips instead of trying to drill these tiny hole myself.
And I am very convinced I will find a proper way of using my new hotend without an additional fan, maybe one to cool the print but not for the hotend itself.
Some parts should arrive this week so I will upload a few pics showing the desgin changes for those interested in building one.

Vespel seems to be a brandname for polyimide. Yes PI is pretty heat resistent, but afaik it has even worse properties than PEEK when it comes to filament sticking to it when hot, so you would still need an inliner. As for nozzles, i use airbrush nozzles with the Merlin hotend, they proved to be simply good and much cheaper than any brass nozzle i know.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

I printed all weekend PET+ using my jhead at 260. I have yet to tear it down to see what it looks like inside. Concerned about the PTFE inside... but i had fan running hard.

Another thought that i have on my list to vet it out is, use a larger stainless object.

Here's the thing about stainless. It conducts heat very slowly. It is less thermally conductive than brass or aluminum. So instead of this really thin stainless tube we have now, what about a big thick stainless bolt with the head cut off or threaded rod and drilled through.. This is what the E3D hotend attempted to do. They used a thicker stainless tube but drilled it halfway through for the PTFE tube. The more metal at the hotend tip slows down heat creep. That's a theory at least. In practice, if the user doesn't control the fat sufficiently, it will still block.

Tried some ABS today and it worked really good until the teflon got too soft.
Printing ABS first try
I think with the PEEK holder and maybe a "stubby" stainless steel heat barrier it should be fine and good to go.
But will make the nozzle quite a bit shorter as with the heat barrier I won't need the long neck which was added to check if the longer melting chamber helps.
As I know now, my problem was not the actual hotend but the filament getting blocked in the stainless steel bolt...