Mylar® OL13T is a biaxially oriented polyester (OPET) film with an amorphous polyester heat seal layer. It is used as a heat sealable lidding film in packaging refrigerated and frozen foods. Mylar® OL13T is dual ovenable film which provides very strong, aggressive seals to polar substrates such as amorphous polyester (APET, also PETG), semicrystalline polyester (CPET), polyester coated paperboard, and polyvinylchloride (PVC). Mylar® OL13T does not seal to polyethylene, polypropylene, or polystyrene. DuPont Teijin Films offers another family of lidding films (RL types) for sealing to these substrates. Mylar® OL13 is similar to OL12 but has a thicker seal layer than Mylar® OL12T to give enhanced seal strength. In general, Mylar® OL13T can produce non-peeling, near "lock-up" type seals and is recommended for hot fill applications where non-peeling seals are desired. It can also be used in some "post-pasteurized" (steam sterilization) applications where the pressure balance in the package can be properly controlled (via vacuum or overpressure). Mylar® OL13T lidding films have excellent grease and oil resistance.

Mylar® OL13T has corona treatment (on the opposite side of film from the heat seal layer) to enhance printing and laminating. The film is treated to an initial dyne level of 54. The dyne level of treated lidding films may decline with storage, and in-line corona treatment may be required during subsequent printing or laminating to increase the dyne level to a value adequate to get desired ink or laminate adhesion.