MIL-PRF-131K Class 3
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 Scrim / PE / Foil / PE layered structure which gives it exceptional tear resistance. Our bags are converted in accordance with MIL-DTL-117.
(Excerpt from the MIL-PRF-131K specification.)
MIL-PRF-131K Class 3 (specialized use). Class 3 is similar to Class 1 but is used for those applications where a higher strength heat-sealable, flexible, watervaporproof, greaseproof barrier material is required..
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.