If it's proper polyimide film, and not like, Idunno, does anyone dye polyester to fake it? I wouldn't put it past them... Needless to say if you're buying no-names from, whatever, Amazon, Ali, eBay... you're gonna get whatever. Maybe it's the real deal, maybe it's an empty box.
Anyway, there's the two parts, as you can see. Polyimide film by itself is incredibly robust, it can survive nearly red hot (for brief periods) before turning to crud. So it's obviously fantastic for soldering.
The trouble is sticking it in place. There's three common adhesives, more or less: rubber, acrylic and silicone, in increasing order of melting point. The first one just bubbles and burns at soldering temp, I think? The second can be used but gets very soft, or bubbly. The last basically shrugs it off, good as at room temp.
The one thing I think silicone adhesive does poorly, is oils. Fingerprints don't go well together, clean everything that's touching it (so, wash your hands or clean with solvent, clean the work etc.).
3M #92 is pretty good, or I think that's what I have, the number wore off it long ago...
Tim