Our MIL-PRF-131K barrier materials protect your products from moisture, oxygen, and contaminants, meeting the U.S. military’s toughest packaging standards.
Available in rolls, sheets, tubing, and custom bags, they’re built for long-term preservation in demanding environments.
As an ISO 9001-certified, veteran-owned small business and GSA contract holder, Protective Packaging delivers compliant, ready-to-use solutions you can trust.
ALL MATERIALS INCLUDE A LAYER OF FOIL
(Formerly MIL-B-131)
| WE CARRY THE FOLLOWING MIL-PRF-131K (FORMERLY MIL-B-131) MATERIALS | ||||
| Material Name | Brand/MFG | Mil Spec | DataSheet | |
| Protect 470 | MS 470 | MIL-PRF-131 Class 1 |
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| Protect 2175 | FR 2175 | MIL-PRF-131 Class 1 |
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| Protect N | Cad Pak N | MIL-PRF-131 Class 1 |
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| Protect P | Cad Pak P | MIL-PRF-131 Class 1 |
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| Protect PL | Cad Pak PL | MIL-PRF-131 Class 1 |
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| Protect 360 | MS 360 | MIL-PRF-131 Class 1 |
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| Protect 100 | HD 100 | MIL-PRF-131 Class 1 |
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| Protect 200 | HD 200 | MIL-PRF-131 Class 1 |
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| Protect 585 | Tyvek 585 | MIL-PRF-131 Class 1 |
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| Protect KF | Kraft Foil 1312 | MIL-PRF-131 Class 2 |
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| Protect SCRIM-B | MS 1311 | MIL-PRF-131 Class 3 |
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| Protect SCRIM-C | Cad Pak S | MIL-PRF-131 Class 3 |
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Available Formats & Customization
Protective Packaging’s MIL-PRF-131K compliant barrier materials are available in rolls, sheets, tubing, and bags. We manufacture bags of all sizes. No bag is too big to protect your mission-critical components.
For fast, custom quotes, call 1-888-972-7157.
About MIL-PRF-131K
MIL-PRF-131K is the U.S. military performance specification for watervaporproof, greaseproof, flexible, heat-sealable barrier materials. These materials are designed for long-term protection against moisture, oxygen, and other environmental contaminants. This standard is approved for use by all Departments and Agencies of the Department of Defense.
Note: The following is an excerpt of the official MIL-PRF-131K performance specification. For the complete and current document, visit the U.S. Department of Defense at assist.dla.mil.
MIL-PRF-131K Performance Specification (Excerpt)
NOT MEASUREMENT SENSITIVE
MIL-PRF-131K – 18 August 2005
Superseding MIL-PRF-131J – 26 August 1998
(Formerly MIL-B-131H)
Performance Specification:
Barrier Materials: Watervaporproof, Greaseproof, Flexible, Heat-Sealable
Scope
This specification covers requirements for heat-sealable, grease proof, flexible barrier materials with low water vapor transmission rates, intended for use in military packaging applications.
Requirements
Qualification: Barrier materials must be authorized by the qualifying activity for listing on the applicable Qualified Products List (QPL) before contract award.
Material: Must be made from materials and by processes that ensure compliance with performance requirements.
Construction: One or more plies; butting not permitted except perpendicular to rolling direction; any butt weld must be flagged with colored markers.
Splices: No more than 3 splices (4 pieces) per roll; each piece at least 45 yards long; splices must be full width and flagged; flat cut sheets cannot contain splices.
Form: Furnished in rolls or flat cut sheets as specified.
Rolls:
- Width: 36 inches (+¼” / −⅛”)
- Average length: ≥200 yards; individual rolls: ≥195 yards
- Cores: nonreturnable, ≥3″ inside diameter (+⅛”), length equal to roll width (+⅛”)
- Rigid cores to prevent distortion; rolls restrained to prevent unwinding
Sheets:
- Length/width as specified; if unspecified: +¼” / −⅛” tolerance
- Uniformly stacked
Sealing: Must be heat-sealed under manufacturer-recommended conditions; seals must not delaminate; each roll/package includes visible sealing instructions for rotary, band, and jaw-type sealers.
Identification of Material: Mark with specification number, class, manufacturer info, date, lot number, and sealing conditions; lusterless red ink; continuous lengthwise; ≤2″ between groups; lettering ≥⅛” high.
Performance Requirements: Must meet specifications in Table I.
Workmanship: Surfaces free of foreign matter; edges trimmed; no holes, tears, cuts, sharp creases, wrinkles, or imperfections.
| Characteristics | Class I Requirements | Class II Requirements | Class III Requirements |
| Seam Strength 1. As received material sealed & tested: a. At room temperature (separation-inches) b. At 100°F and at 160°F (separation-inches) 2. Sealed before aging at 160°F for 12 days and tested: a. At room temperature (separation-inches) b. At 100°F and at 160°F (separation-inches) 3. Sealed after aging at 160°F for 12 days and tested: a. At room temperature (separation-inches) b. At 100°F and at 160°F (separation-inches) | No separation ¼ (Max) No separation ¼ (Max)No separation ¼ (Max) | No separation ¼ (Max)No separation ¼ (Max)No separation ¼ (Max) | No separation ¼ (Max)No separation ¼ (Max)No separation ¼ (Max) |
| Seam Fabriacation | No leakage at double seam junction | Not required | No leakage at double seam junction |
| Water vapor transmission Rate (WVTR) 1. After room temperature flexing: a. As received (gms/100 sq. in./24 hrs.) b. Aged (gms/100 sq. in./24 hrs.) 2. WVTR after low temperature flexing: As received (gms/100 sq. in./24 hrs.) | 0.02 (max) 0.02 (max)0.03 (max) | 0.02 (max) 0.02 (max)Not required | 0.02 (max) 0.02 (max)0.03 (max) |
| Breaking strength (Grab Method) a. As received (weakest direction) (lb/inch) b. After aging (weakest direction) (lb/inch) | 50 min 50 min | 25 min 25 min | 65 min 65 min |
| Water vapor transmission rate (WVTR) (Modulated Infrared Sensor)As received (gms/100 sq. in./24 hrs.) | .0005 (max) | .0005 (max) | .0005 (max) |
| Puncture Resistance (lbs) | 15 min | 6 min | 22 min |
| Tear Strength (lbs) | Not Required | Not Required | 17 min |
| Backing Peel Strength (oz/in) | Not Required | Not Required | 7.0 (min) |
| Aging Resistance | No delamination as specified in 4.6.3.1 | ||
| Blocking Resistance | No blocking, delamination, or rupture | ||
| Resistance to curl | No curl in excess of 5% or curl back upon itself | ||
| Contact Corrosivity | No corrosion, etching, or pitting | ||
| Oil Resistanc (Delamination) | No leakage, swelling, delamination, or embrittlement | ||
| Water Resistance | No delamination | ||
| Water Resistance of Marking | Markings on back of sheet shall be clear and legible | ||
Common Applications for MIL-PRF-131K Barrier Materials
Our MIL-PRF-131K compliant packaging materials are trusted wherever environmental control and moisture protection are essential, particularly in specialized military methods of preservation.
These materials combine seam strength, fabrication quality, low water vapor transmission rate, breaking strength, puncture resistance, blocking and curl resistance, contact corrosivity, delamination resistance, and water-resistant markings to meet the extreme demands of navy and naval aviation environments.
Navy and naval aviation items face high moisture, high salt concentration, transfer at sea, rough handling, and minimal storage conditions. There are no commercial equivalents that match the physical, mechanical, and corrosion protection needed for such conditions. For this reason, Methods 41, 42, 43, 51, 52, and 53 of MIL-STD-2073-1 designate MIL-PRF-131 as the premier barrier material for watervaporproof (and watervaporproof with desiccant) protection.
Typical applications include:
- Long-term preservation of military and aerospace parts, where performance over years of storage is mission-critical.
- Protection of sensitive electronics during transport and warehousing to prevent corrosion and ESD damage.
- Export packaging for international shipments exposed to fluctuating climates and rough handling.
- Industrial equipment storage, from heavy machinery to precision components, especially in humid or coastal locations.
By maintaining low moisture vapor transmission rates, these barrier materials ensure that products arrive and remain in perfect condition.
MIL-PRF-131K Classes and Intended Uses
Class 1 (General Use): Plastic non-woven backing. Suitable for all packaging applications requiring heat-sealable, flexible, watervaporproof, greaseproof barrier materials.
Class 2 (Limited Use): Kraft backing. For packages where the combined weight inside the barrier does not exceed 10 pounds and the inside length plus width does not exceed 42 inches. Not recommended for floating bag applications, packaging below 32 °F, or double seam junctions. To prevent cracking or pin-holing, packages should not be handled below 32 °F.
Class 3 (Specialized Use): Similar to Class 1, but designed for applications where a higher-strength heat-sealable, flexible, watervaporproof, greaseproof barrier material is required.
Why Choose Protective Packaging for MIL-PRF-131K Solutions
When your operation requires compliance with military packaging standards, experience and precision matter. At Protective Packaging, we combine decades of expertise with in-house manufacturing capabilities to deliver barrier materials that meet or exceed MIL-PRF-131K performance requirements.
Our team understands the stakes when failure is not an option, and we work closely with clients to ensure every order matches their operational needs. As an ISO 9001-certified, veteran-owned small business and GSA contract holder, we provide more than products — we deliver confidence in every shipment. From roll stock to complex custom conversions, our solutions are backed by rigorous quality control and a commitment to on-time delivery.
Ordering & Customization
Every project is different, which is why we offer flexible ordering options to match your application: standard rolls, pre-cut sheets, tubing, or custom-sized bags. Whether you need packaging for small electronics or oversized aerospace assemblies, our production team can configure your order to meet exact specifications.
To discuss your requirements or request a quote, call us at 1-888-972-7157 or use our online contact form. Our specialists are ready to help you select the right MIL-PRF-131K barrier material and ensure it’s delivered in the format you need and it’s ready for immediate use.
As noted previously, this military specification has gone through multiple revisions and the version nomenclature is updated with each change. This specification has been known as:
- MIL-B-131
- MIL-B-131H
- MIL-PRF-131
- MIL-PRF-131J
- MIL-PRF-131K (This is the current standard adopted in August of 2015.)