Importance

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Abstract

Heat-sealable thermoplastic elastomeric films comprise from approximately 35% to about 65% of an A-B-A block copolymer wherein 'A' blocks are derived from polystrene or a polystrene homolog and said 'B' blocks being derived from lower alkenes and from about 25% to about 55% of an ethylene vinyl acetate copolymer, the ethylene vinyl acetate copolymer comprising approximately 28% vinyl acetate. The films are heat-sealable to various substrates including polyvinyl chloride. Once sealed to the substrate, the film may be readily peeled from the substrate by the application of a low and relatively constant peel force. A method for measuring the peel strengths of the film is disclosed. The films are especially adapted to being heat-sealed to a substrate which forms, together with the substrate a package, or multiple serially connected packages. Since the films may be peeled from such a substrate by the application of a low and relatively constant peel force, the films may be peeled from the substrate and the packaged articles extracted from the compartments in a controlled manner. Shear forces generated by flexing or winding the substrate are absorbed by the films without affecting the seal formed with the substrate.

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First Claim