How to control the breathability of aluminum foil steaming bags?

The air permeability control of aluminum foil steaming bags needs to be comprehensively controlled from multiple aspects such as material selection, composite process, and testing standards. The specific methods are as follows:

Quality control of aluminum foil materials

Pinhole control: The number and aperture of pinholes in aluminum foil directly affect its barrier properties. The number of pinholes in 7 μ m thick aluminum foil should be less than 200 per square meter, and the number of pinholes in 9 μ m thick aluminum foil should be less than 100 per square meter, with a pore size of ≤ 20 μ m

High purity aluminum raw materials (purity>99.5%) and clean production environment can reduce the occurrence of pinholes.

Thickness and cleanliness: recommended thickness of 7-9 μ m, thickness deviation ≤ 7%

The surface needs to achieve A/B level cleanliness and pass the distilled water immersion test (with no oil residue).

Composite process optimization

Adhesive selection: High temperature resistant two-component polyurethane adhesive should be used to ensure compatibility with aluminum foil and other substrates (such as PET, CPP), avoiding interface delamination due to incompatibility.

Glue application amount and curing: The glue application amount should be ≥ 4g/m ², and the curing time should be ≥ 72 hours to eliminate internal stress and enhance composite strength.

Production process parameters

Annealing process: The temperature (250~400 ℃) and time (10~80 hours) of the finished product annealing need to be strictly controlled to ensure the flexibility and surface oil removal effect of the aluminum foil.

Heat sealing layer material: The heat sealing layer adopts RCPP or SCPP film (thickness ≥ 60 μ m), and its shrinkage rate is controlled (longitudinal/transverse ≤ 1.5%).

Testing and Standards

Evaluate packaging performance through air permeability testing (such as ISO standards) and select air permeability levels (general/advanced/special) based on product requirements.

Verify the composite peel strength (e.g. PET/AL must be ≥ 4.5N/15mm) and high temperature resistance (e.g. no delamination after cooking at 121 ℃).

In summary, the air permeability control of aluminum foil steaming bags needs to be strictly controlled throughout the entire process from source materials, process parameters to finished product testing to ensure barrier performance and packaging safety.