OTR/WVTR Performance of Side Gusset Flat Bottom Bags
Oxygen Transmission Rate (OTR) and Water Vapor Transmission Rate (WVTR) are important indicators of the barrier performance of side gusset flat bottom bags. Effective barrier control helps protect packaged products from oxidation, moisture absorption, aroma loss, and environmental exposure, supporting product quality and shelf life.
OTR Performance
OTR measures the amount of oxygen passing through a packaging material under specified conditions, commonly expressed in cm³/m²/day. A lower OTR generally indicates stronger oxygen barrier performance.
For coffee, tea, nuts, snacks, powdered foods, and other oxidation-sensitive products, a low OTR structure can help reduce exposure to oxygen. PET, metallized films, aluminum foil, and specialized barrier layers can be combined to achieve different protection levels.
WVTR Performance
WVTR measures the transmission of water vapor through packaging materials and is commonly expressed in g/m²/day. Lower WVTR values indicate better moisture barrier performance.
Strong moisture protection is particularly important for powders, dehydrated foods, spices, and moisture-sensitive products. An appropriate barrier structure can help prevent caking, texture changes, and quality deterioration.
Effect of Gusset Structure
The side gusset and flat-bottom configuration can introduce additional folds and sealing areas. Although the film itself may have excellent barrier properties, folding, creasing, sealing, and mechanical stress can influence overall package integrity.
For high-barrier applications, the complete bag should be evaluated rather than relying only on the barrier data of individual film layers.
Material Structure
Common structures may combine PET or BOPP outer layers with PE or CPP sealant layers, while metallized films or aluminum foil can be incorporated when higher barrier protection is required.
Material selection should consider product sensitivity, target shelf life, storage humidity, temperature, filling conditions, and transportation requirements.
Testing and Quality Control
OTR testing can be performed according to ASTM D3985, while WVTR testing may follow ASTM F1249 or ISO 15106. Test temperature and relative humidity should always be specified because environmental conditions can significantly affect test results.
Finished bags should also undergo seal-strength and leak testing, since weak seals or damaged folds may compromise practical package performance even when the film has excellent barrier properties.
Performance Optimization
The ideal structure balances barrier performance, mechanical strength, sealing reliability, material efficiency, and cost. Prototype testing with the actual product is recommended before mass production to confirm that the selected structure can meet the required shelf-life target.
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
ISO 15106 – Plastics — Film and Sheeting — Determination of Water Vapour Transmission Rate
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
