I think it's PTFE but regardless of acronyms, I don't think that a fluoroplastic coating is appropriate for such a high temperature.  As far as I know, there is no plastic/fluoroplastic coating acceptable for temperatures that high.  

You might buy a little more time with a thicker sheet but at 327 Celsius, a 1mm coated sheet gets you two minutes.  You want to get more than 7 at more than 1100 Celsius.  The coating would essentially not be a coating, it would be a have to be a prohibitively huge amount of plastic with a sheet steel coating and then there's the potential issue of what you do with all the teflon you just burned off?  

Can you give more details on what you're trying to do.  How small is the diameter?  There are several metals that can handle the temperature, what is so corrosive that mandates the use of teflon?    

Thankyou for the answer Clvet. We have dropped telflon sheet idea.

FYI: the sheet was going to be used against liquid iron short exposure. Which obviously is not possible with teflon ( now we know ).
We will opt for our conventional way of using refractory coatings ( BN or Zr, water based ) instead of teflon.