Table of Contents
Reviewed and updated by ICD - Week 30/2026
Quick summary:
- A container dunnage bag is built from three specialized materials: a load-bearing outer shell, an air-holding inner bladder, and a valve.
- Outer shell: multi-ply kraft (economical, mild moisture resistance, Level 1-3) or woven PP (very high load, reusable, Level 3-5).
- Inner bladder: a PA/PE composite film - PA is the gas barrier that holds pressure, PE adds toughness and heat-sealing.
- Valve: load-bearing PE/PP or nylon, with a fast type that optimizes inflation speed and holds working pressure.
The 3 materials of a container dunnage bag
A dunnage bag is a high-engineering product whose multi-layer structure resists compression, abrasion and impact over a long voyage. For the full layer breakdown, see structure and types; here we focus on the materials themselves.
Outer shell: strength and abrasion resistance
The outer shell touches the goods and container wall and sets the bag’s AAR level.
| Material | Traits | Load & use |
|---|---|---|
| Kraft paper | 2-6 plies, PP-laminated for moisture and friction | Level 1-3. Medium loads, square boxes. More plies = better static compression. |
| Woven PP | Cross-woven, dense, waterproof, very high tensile strength | Level 3-5. Very heavy, sharp-edged, reusable. |
Kraft paper is favored for economy and its natural friction (the bag does not slip), but it resists moisture less well; in humid sea transport its strength can drop slightly. The outer PP lamination limits water absorption and stops fiber tearing under high compression, keeping the bag intact. See what kraft paper is.
Woven PP is optimal for heavy loads with high impact and abrasion risk. Its cross-weave spreads shear force and resists tearing extremely well, making it the only material that survives rail shunting without failing. Its tensile strength is many times that of kraft, so the bag does not over-deform under large dynamic compression. See what woven PP fabric is.
Inner bladder: air retention
This layer seals the compressed air and holds the static pressure for the whole journey. It is usually a PA/PE composite film:
- PA (polyamide): the key gas barrier - air molecules (nitrogen, oxygen) diffuse through it very slowly, so the bag keeps stable pressure even as container temperature changes, preventing slow deflation over a 4-8 week voyage.
- PE (polyethylene): adds toughness and good heat-sealing - it takes the tension of inflation and impact without tearing, and forms the heat seal that closes the bag.
The PA/PE film thickness directly affects lifespan and pressure retention - thicker film resists gas diffusion and pressure differences better - and the heat-seal quality matters as much as the material.
Valve: pressure and speed control
The valve is high-grade engineering plastic (load-bearing PE/PP or nylon) that withstands continuous pressure and container temperatures. A fast valve (20-30 mm) inflates 2-3x faster and auto-locks; an internal rubber gasket gives the leak-free seal. See the dunnage bag valve guide.
Frequently Asked Questions (FAQ)
What is the inner bladder made of?
A PA/PE composite film. PA is the gas barrier that holds pressure; PE adds toughness and the heat seal.
Why does kraft need a PP lamination?
To limit moisture absorption and stop fiber tearing under high compression, keeping the bag intact in humid transport.
Which material reaches the highest AAR level?
Woven PP - its tensile and tear strength let it reach Level 3-5, the only material that survives rail shunting.
What is the valve made of?
Load-bearing PE/PP or nylon with a rubber gasket, resistant to ageing and container temperatures from -20C to 50C.
Contact ICD Viet Nam
For dunnage bags in the right material for your cargo, contact our team for a quote.
- Northern Vietnam: 0983 797 186 / 090 345 9186 / 090 5859 186
- Southern Vietnam: 098 6784 186
- Email: sales@icdvietnam.com.vn
- Zalo: Chat on Zalo
Dunnage Bag Material Comparison: Kraft Paper vs PP Woven
The outer shell of a dunnage bag is either kraft paper (1 to 6 plies) or PP woven fabric. The inner bladder is always a PE film layer that holds compressed air - this component does not change between the two types. The choice of outer shell determines moisture resistance, applicable standards, and total cost.
| Property | Kraft Paper | PP Woven |
|---|---|---|
| Outer layer material | Multi-layer kraft paper (1-6 ply) | Polypropylene woven fabric |
| Inner bag | PE film bladder | PE film bladder |
| Moisture resistance | Low - paper absorbs moisture | High - fabric repels moisture |
| Typical application | Rail freight (AAR OT-55) | Sea container, humid conditions |
| Cost | Lower | Higher |
| AAR Level range | Level 1-3 depending on ply count | Level 2-3 |
For exporters shipping by sea container from Vietnam, PP woven dunnage bags are the more practical choice. Containers experience condensation and humidity fluctuations during transit, particularly on long routes to Europe or North America. Kraft paper degrades when wet, which risks losing the inflated shape and cargo protection mid-voyage. ICD Vietnam supplies both types but PP woven accounts for the majority of orders from Vietnamese exporters precisely for this reason.
Frequently Asked Questions
What materials are dunnage bags made of?
Dunnage bags have two key layers: an outer shell made of either kraft paper (1 to 6 plies) or PP woven polypropylene fabric, and an inner PE film bladder that holds the compressed air. The bladder material is the same across both outer shell types. The outer shell determines the bag’s strength rating, moisture tolerance, and applicable freight standard. Kraft paper versions are rated under the AAR OT-55 standard for North American rail, while PP woven bags are widely used for sea and intermodal freight where moisture is a factor.
Which is better - paper or PP woven dunnage bags?
PP woven bags perform better in sea freight and humid environments because polypropylene fabric does not absorb moisture, maintaining full inflation and load-bearing capacity throughout the voyage. Kraft paper bags are a more economical choice for dry rail freight environments where humidity is controlled and AAR OT-55 certification is required. For most Vietnamese exporters shipping to Europe, the US or Australia by sea container, PP woven is the safer and more durable option despite the higher unit cost.
Can dunnage bags be reused?
Paper dunnage bags are single-use by design - the kraft layers compress and weaken after one inflation cycle and should not be re-inflated. PP woven bags can sometimes be re-inflated if the outer fabric and valve show no visible damage, but industry practice is typically single-use per shipment for liability reasons. Cargo damage claims become complicated if a reused bag fails during transit. Most logistics managers treat dunnage bags as a consumable cost rather than a reusable asset, similar to stretch film or packing tape.
