Active Packaging for Microwave Food

Has anyone had experience with active packaging in microwaveable food products? Other than cooking lunchtime snacks, of course! Some of the more common tradenames are qwik crisp, quilt wave, etc. I was wondering what the material is that is laminated to the paperboard, if it is a metal foil, metallized mylar, or if it is a proprietary trade secret. Ideas anyone? Yes, I know there are numerous companies that supply this packaging, but that doesn't satisfy my curiosity to know what the stuff is.