Polaroid 665 is an endangered species since it is no longer being manufactured. But according to everything I have read, it is a very conventional photographic product. At one time, the film was reported to be Kodak Pan-X, their very fine grain ASA50 emulsion, married with Polaroid's proprietary developing gel system and expensive packaging.
On that basis, I would think that the amount of damage that the x-rays used to screen carryon stuff would not cause a significant problem, but you definitely don't want to put it in your checked luggage.
But there is another potential problem - with the airlines now paranoid about various liquid and gel products, there is at least some risk that the screener might know that 665 package contains a developing gel and refuse to allow you to carry it on the plane. The probably that a screener would be that clueful is pretty remote, but if you lose the bet, you lose the film.
How had you planned to deal with transporting something to clear the negatives after processing?
Shipping it to yourself might be the best alternative if you can be assured that the shipper won't x-ray the package.
