I just got my order of the Capricorn PTFE tube, and I have to say that it really does have lower friction than a “normal” PTFE tube.
Anyone else using it?
I’m not using it for a bowden tube, just planning to use it inside the E3D v6, but it should still help I think.
I am not in any way affiliated 
https://www.filastruder.com/products/capricorn-ptfe-tubing
No idea, but they list the ‘stiffness’ as being medium when the other stuff is high. This may very well be more elastic than typical PTFE tubing, which is a bad thing. I’m wondering what it is they managed to add that supposedly brought the temperature resistance up though. I haven’t tried it, but I am suspicious of their claims.
To me the stiffness feels just like any of other ptfe tubes I have lying around. I’m slightly concerned that maybe it has lower temperature tolerance (for use inside hotend), but I’ll just test and see how it works.
I am using a section of their translucent blue as a feed tube. It’s nice but it doesn’t seem any slipperier than the stuff I get from McMaster-Carr. It is snugger but that can be a concern with bowden as the hobb roughing up the material makes it bigger.
Black, higher temp resistance, stiffer, and lower friction? I’d bet it’s a graphite fill. I use graphite fill PTFE at work sometimes and it’s really good stuff. Molybdenum disulfide is also sometimes used as a PTFE fill but that’s pricier.
I have the xs (non translucent) version and it’s more of a solid dark blue color. I still evaluating it, but ithas lowered my retraction amount due to the smaller inside diameter.
FWIW, there is very little that you can do to PTFE chemically ( I believe there are only 2 or 3 common copolymers with PTFE - FEP and PFA are the 2 I’m familiar with), so it’s either a filled PTFE or a copolymer and thus not actually true PTFE.
Both FEP and PFA have similar friction coefficients, and are generally cheaper because they’re easier to work with.
It was too thick to go inside mk10 Flashforge extruder I might tty thinning it out slightly. It’s just a hair off.
Hmm really? It fits just fine inside an E3D V6, but I’m not sure if I can tell the difference 
Maybe I had some filament leak into the throat.