a base thermoplastic film , has a coextruded or coated heat seal layer formed from a polymer blend which provides good peel - apart heat seals . when the film is sealed to itself , the seal opens by separation at the original seal surface without film tear , or by delamination of the sealant material from the primary base film substrate without the formation of strands extending between the two base film . the heat seal layer which may be on one or both sides of the base layer comprises a ternary blend of a random ethylene - propylene copolymer , a butene polymer and a low density polyethylene . the films are cast , and oriented in the solid state up to about two times in the machine direction and six times or more in the transverse direction to give films having good dead - fold and water vapor transmission rate characteristics making them highly suited for packaging , particularly for dry foods .