Data provided by DuPont Packaging Polymers.Mylar® RL4 is a biaxially oriented polyester (OPET) film with an ethylene vinyl acetate (EVA) heat seal layer. It is used as a heat sealable lidding film in packaging frozen and refrigerated foods. Mylar® RL4 is designed to seal to a broad range of container substrates including amorphous polyester (APET, also PETG), semicrystalline polyester (CPET), polyester coated paperboard, polyvinylchloride (PVC), polyethylene (HDPE), polypropylene (PP), and polystyrene (HIPS). The thickness of the heat seal layer and the heat seal strength of Mylar® RL4 is intermediate between Mylar® RL31 and Mylar® RL33. Mylar® RL4 and Mylar® RL32 produce similar heat seal strengths to most substrates, but Mylar® RL32 has a greater tendency to produce tearing seals while Mylar® RL4 tends to produce more peelable seals. Mylar® RL4 has a lower seal initiation temperature than lidding films with an amorphous polyester heat seal layer (e.g., Mylar® OL, OL2). This allows good seals to be made at higher line speeds (or using lower sealing temperatures).