Its my understanding that Teflon / PFTE is GTG anywhere ... except the bore. This quote is about PFTE gun lubes, but I would venture to guess the same applies to Teflon sabots...
"The combustion process releases hydrofluoric acid from the PTFE polymer, and the HF ACID EATS THE STEEL.
Weakens the steel, etches the steel, promotes brittle stress fractures due to hydrogen embrittlement, etc.
That is a bad thing. Much the same as shooting corrosive ammo out of your gun, and not cleaning it properly afterwards.
PTFE is harmless at room temperature, but above 600F it breaks down, and begins outgassing. Transient temperatures seen during combustion in the bore are considerably higher than that, at ~3000F. Plenty hot to burn microparticulate PTFE into its combustion byproducts.
Why accelerate your bore wear and reduce the overall effectiveness of your weapon using PTFE lubes in the bore when molydisulfide and other bore lubes are so vastly superior and have no deleterious side effects??
PTFE containing lubes are fine for non combustion areas, but keep them out of the bore! "
The above referenced quote is about modern 50K pressure use..... I have no idea if if applies to Black Powder Muzzle loaders using sabots.