Barrier Performance of Vacuum & Three-Side Seal Bags
Barrier performance is a critical factor in vacuum and three-side seal bags because the packaging must protect the product from oxygen, moisture, light, aroma loss, and external contamination. A suitable barrier structure can help maintain product quality and extend shelf life under the intended storage conditions.
Oxygen Barrier Performance
Vacuum packaging reduces the amount of air inside the bag, but it does not completely eliminate oxygen exposure. Therefore, the film should provide an appropriate Oxygen Transmission Rate (OTR) for the packaged product.
Low-OTR structures are commonly considered for meat, seafood, cheese, coffee, nuts, and other oxygen-sensitive products. PET, metallized films, aluminum foil, and specialized barrier layers can be combined to achieve different oxygen protection levels.
Moisture Barrier Performance
Water Vapor Transmission Rate (WVTR) measures the movement of moisture through the packaging material. Low WVTR is important for products that are sensitive to humidity or moisture loss.
Dry foods, powders, processed foods, and moisture-sensitive products may require enhanced moisture protection. The selected structure should be evaluated under temperature and humidity conditions representative of actual storage.
Effect of Vacuum Packaging
Vacuum removal places the film under mechanical stress and causes the package to conform closely to the product. This can increase the risk of puncture, flex cracking, seal stress, and channel leakage.
Barrier performance should therefore be considered together with mechanical durability. A film with excellent laboratory barrier properties may not provide adequate practical protection if it is easily damaged during vacuuming or transportation.
Three-Side Seal Integrity
The three sealed edges are critical barrier points. Incomplete seals, wrinkles, contamination, and insufficient seal strength can create leakage paths and compromise the package.
Seal strength should be verified according to ASTM F88/F88M, while suitable leak testing can be performed according to ASTM F2096 or ASTM D3078.
Material Structure
Common vacuum bag structures may use PET/PE, PA/PE, or higher-barrier laminated constructions. PA can provide useful mechanical and puncture resistance, while PE commonly provides heat sealing.
For applications requiring stronger oxygen and moisture protection, aluminum foil or metallized barrier layers may be incorporated.
Testing and Validation
OTR testing can be performed according to ASTM D3985, while WVTR testing may follow ASTM F1249 or ISO 15106. Vacuum retention, puncture resistance, seal strength, and leak testing should also be considered.
Performance Optimization
The ideal vacuum bag structure balances barrier protection, mechanical strength, sealing reliability, flexibility, and cost. Testing with the actual product and vacuum equipment is recommended before mass production.
References
ASTM D3985 – Standard Test Method for Oxygen Gas Transmission Rate Through Plastic Film and Sheeting
ASTM F1249 – Standard Test Method for Water Vapor Transmission Rate Through Plastic Film and Sheeting
ASTM F88/F88M – Standard Test Method for Seal Strength of Flexible Barrier Materials
ASTM F2096 – Standard Test Method for Detecting Gross Leaks in Packaging by Internal Pressurization
ASTM D3078 – Standard Test Method for Determination of Leaks in Flexible Packaging by Bubble Emission
ISO 15106 – Plastics — Film and Sheeting — Determination of Water Vapour Transmission Rate
