Ned Simmons writes:

No confusion, note that I referred to Turcite and Rulon as
families of materials.

Right, I was confusing another's comment citing "turcite" as if it were
a single thing.

You did say they were filled or reinforced PTFE. I found one reference
today that identified one Rulon as ECTFE.

See my earlier comment on the specific gravity of Turcite
B. The higher density would be consistent with a metal
filled PTFE.

See my earlier reference to the MSDS, which doesn't list any metal
content in any proportion that would increase density.

But if you're right, then that would require about 10 to 15 percent
metal by volume, depending on the metal.

It seems you're misusing the term copolymer.

No, I said "copolymer or blend" (too lazy to check which). You're
correct, it is the latter.

Rulon 142, which is claimed to be a direct replacement for Turcite B
is
definitely *not* just PTFE.

So what is it, then?

One thing that I worry about on my machines is the fact
that once grit or a particle gets imbedded in the plastic
it'll likely get dragged back and forth for a long time.

They claim that is actually a benefit, that particles embed at or below
the surface so as to encapsulate and not wear the opposing metal.

And of course this is a problem with metal/metal bearings. There was a
deep score in the Bridgeport knee way I'm rescraping, and I eventually
discovered (only by the disassembly and scraping process) a single tiny
grain of carbide or diamond had been embedded in the opposing surface.