Key Physical Performance Indicators of Aluminum Foil Pouches-Water Vapor Transmission Rate and Oxygen Transmission Rate
Water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) are critical physical performance indicators when selecting aluminum foil pouches. These metrics measure the total amount of water vapor or oxygen passing through a unit area of the material over a specific time period. Lower transmission rates indicate better barrier performance.
The barrier effectiveness of aluminum foil bags primarily depends on the thickness of the aluminum foil layer. Thicker aluminum foil results in fewer pinholes and superior barrier properties against moisture and oxygen.
Aluminum foil surfaces naturally contain irregular pinholes ≤300μm in diameter
Most manufacturers use 5.8-6.3μm foil to reduce costs:
• 5.8μm foil: 500-600 pinholes/m²
• 6.3μm foil: 300-400 pinholes/m²
(Both exhibit inadequate barrier performance)
7μm foil contains <100 pinholes/m², significantly improving moisture/oxygen resistance.
Extensive field experience has demonstrated that only aluminum foil with thickness ≥7μm can meet the required specifications:
Water vapor transmission rate ≤0.03g/m²·24h
Oxygen transmission rate ≤0.03cm³/m²·24h·0.1MPa