| 摘要 |
An opaque barrier layer which comprises: (a) at least one thermoplastic polymer matrix substrate layer within which is located a strata of voids; positioned at least substantially within at least a substantial number of said voids is at least one spherical void-initiating particle which is phase distinct and incompatible with the matrix material, the void space occupied by said particle being substantially less than the volume of said void, with one generally cross-sectional dimension of said particle at least approximating a corresponding cross-sectional dimension of said void; and, (b) at least one thermoplastic water vapor transmission barrier layer affixed to said thermoplastic substrate layer.
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