What is the structure of cryovac film?

Cryovac is a registered trademark of the Sealed Air Corporation. Cryovac films are made up of multiple layers of plastics resins which are capable of preventing certain gases and/or moisture getting in or out of the sealed package. For example, oxygen reacts with meat to make it go off, so a Cryovac meat film, correctly used, will keep the oxygen out of the pack to extend the usable life of the meat and prevent wastage.