Dow Corning Corporation

Sarah E Lindsey

Andrew H Ward

James R Falender

Thomas C Kendrick

The gas permeability of a polymeric material is altered by irreversibly mechanically stressing in at least one direction a polymeric material which is a mixture of two phases where one phase is evenly distributed throughout a second phase and one phase is present in an amount of at least 10 weight percent. The phases are polymeric materials which each have an elastic shear modulus of less than 10.sup.9 dynes per square centimeter at processing temperature, are chemically dissimilar materials and have oxygen gas permeabilities which differ by a factor of at least 10. At least one phase is a thermoplastic which is solid at ambient temperature and the mixture retains its physical state on standing at ambient temperature over extended periods of time. An example would be cold rolling a sheet of a polyblend of polyethylene and polydimethylsiloxane. Mechanically stressing film in at least one direction by cold rolling, drawing or blowing polymeric materials as defined above alters the gas permeability from unstressed film. An extruded tube of polymeric material mechanically stressed in at least one direction has altered gas permeability compared to an unstressed tube.

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Midland, MI, United States of America

Sarah E Lindsey