Nomex is a specific type of material. Its designed to melt and close off the pores of the material, once it reaches a certain temp, or is hit with direct flame.
I have looked into finding a material to make a knife handle out of, as I work with a couple of volunteer fire departments and first responders, on gear and training. It doesn't exist. At least from what we have seen, it needs to be either steel, or asbestos to stand up to what fireman do.
Firesuits need to be replaced at regular intervals, so getting nomex wouldn't be that hard. I think it would act like any other "synthetic" material that is turned into micarta.
I will say this, you better wear full face and have a seperate O2 feed to it, if you are going to render nomex airborne, though. That shit will kill you if you breath it.
I think burlap or canvas micarta is still the best.
Moose