Gomer is right, Sikorsky used Kapton for the S-76 until about S/N 80 or so. Kapton is lighter, but more brittle, and must not be bent sharply. Special strain relief connectors are used to help it last.
It is approved, and it works, but it takes more care, and has more problems. It has very good high temp capabilities, and is used extensively in many industrial applications. Ariane 5 has it extensively!
http://www.dupont.com/kapton/