Compositions of matter, sheet material, and packages made therefrom. Novel compositions of polypropylene and high density polyethylene are useful as sealant materials for flexible sheet material structures wherein the sheet material is sealable to a preformed container, to form a lid therefor, and is peelable therefrom, with cohesive failure of the sealant layer in the area of the formed seal. The novel sealant layer compositions provided for package closure and sealing which is capable of withstanding retort conditions while maintaining the integrity of the package closure and seal. Concurrently the lid is readily peeled from the package to provide access to the interior of the package. The peelability comprises cohesive failure of the sealant material in a novel blend of a polypropylene polymer with an ethylene polymer having a density of at least 0.940. The novel sealant materials of the invention can be used on a variety of multiple layer sheet material substructures, and particularly those providing barrier properties to food type packaging: especially barrier to the transmission of oxygen and moisture. Typical barrier materials are metal foil, vinylidene chloride copolymer, vinyl alcohol copolymer, olefin polymers and copolymers, and combinations of the above materials.