Mylar® OB12 is a biaxially oriented polyester (OPET) film with an amorphous polyester heat seal layer and polyvinylidene chloride (PVDC) layer on the opposite side of the film from the heat seal layer. Mylar® OB12 is essentially Mylar® OL12 with a barrier layer. Mylar® OB12 is dual ovenable film which provides strong, aggressive seals to polar substrates such as amorphous polyester (APET, also PETG), semicrystalline polyester (CPET), polyester coated paperboard, and polyvinylchloride (PVC). Mylar® OB12 does not seal to polyethylene, polypropylene, or polystyrene. DuPont Teijin Films offers another family of lidding films (RB types) for sealing to these substrates.

Mylar® OB12 has higher hot tack and a thicker seal layer than either Mylar® OB02 or OL2, and can be used in hot fill applications. It is not recommended for applications requiring retort sterilization. Mylar® OB12 lidding films have excellent grease and oil resistance. Heat seals produced with Mylar® OB12 are stronger than with Mylar® OL2 and may be difficult to peel without shredding at any gauge. Mylar® OB12 is recommended for applications needing a lidding film which heat seals like Mylar® OL12, but with much lower permeability to gases (oxygen, carbon dioxide) and moisture.