MIL-PRF-131K Class 2
MIL-PRF-131K Class 1 is a flexible, heat-sealable material with a low a MVTR that is intended for use in applications that require a moisture barrier. It features a Paper / PE / Foil / PE layered structure. Our bags are converted in accordance with MIL-DTL-117.
(Excerpt from the MIL-PRF-131K specification.)
MIL-PRF-131K Class 2 (limited use). Class 2 material with kraft backing is used for packages where the combined weight inside the barrier does not exceed 10 pounds. Class 2 material should be limited to use in bags whose inside length plus width does not exceed 42 inches. Class 2 materials should not be used in floating bag applications, in packaging operations under low temperature conditions, below 32 °F where fabrication or manipulation of the material is required, or where a double seam junction is fabricated. To prevent cracking and pin holing, packages fabricated from this material should not be handled at temperatures below 32 °F.
Intended use – The barrier materials covered by this specification are intended for use in specialized military methods of preservation. The combination of all performance characteristics of MIL-PRF-131; seam strength and fabrication; water vapor transmission rate; breaking strength; puncture, blocking and curl resistance; contact corrosivity; delamination; and water resistance of markings provide the necessary requirements for protection from exposure to the extremes of the navy/naval aviation environment. Navy/naval aviation items are exposed to high moisture, high salt concentration, transfer at sea, rough handling, and minimal storage conditions. There are no commercial equivalents that meet the physical, mechanical, and corrosion requirements necessary to protect materiel that is exposed to the operational naval aviation environment. Specifically, Methods 41, 42, 43, 51, 52, and 53 of MIL-STD-2073-1 use MIL-PRF-131 as the premier source of barrier materials that provide watervaporproof (and watervaporproof with desiccant) protection for applicable items encountering the above conditions.