1. Significance of Aluminized Layer Thickness
While aluminum foil (generally 7 to 15 microns) offers an excellent barrier, its high cost and tendency to form pinholes during flexing limit its use. Aluminized films solve these issues by depositing a microscopic layer of aluminum onto substrates like PET or BOPP. This significantly enhances the barrier property of the base film while maintaining flexibility and reducing costs.
Because the aluminum layer is so thin, even minute variations in thickness—often measured in Angstroms (?)—can lead to substantial differences in how well the film blocks water vapor. Understanding this relationship is vital for food, pharmaceutical, and cosmetic packaging, where shelf-life is directly tied to moisture control.
2. Test Samples and Standards
For this evaluation, two VMBOPP film samples were tested:
- Sample A: Coating thickness of 4.44μ
- Sample B: Coating thickness of 5.2μ
The testing was conducted in accordance with ASTM F1249, ISO 15106-2, and GB/T 26253, ensuring that the data is globally recognized and standardized.
3. The Testing Instrument: LabthinkC303H
The C303H Water Vapor Transmission Rate Test System was selected for its high precision and intelligent control features.
- Test Principle (Infrared Sensor Method): The test specimen is mounted in the diffusion cell, which is divided into a dry chamber and a controlled-humidity chamber. The dry side of the specimen is swept by a flow of dry nitrogen, and the water vapor permeating through the specimen from the controlled-humidity chamber is carried by dry nitrogen to the infrared sensor where proportional electrical signals will be generated. The water vapor transmission rate is obtained by analyzing and calculating the electrical signals. For whole package specimens, the dry nitrogen flows inside the specimen while the outside of specimen is maintained in a high humidity environment.
- Key Specifications:
- Precision: A high repeatability of 0.05 g/(m2·day).
- Efficiency: Features an independent three-cells integrated block, allowing for the simultaneous testing of three specimens under identical conditions.
- Technology: 360° air circulation constant-temperature technology ensures the thermal stability required for accurate data.
4. Test Process
- Preparation: Three specimens are cut from each VMBOPP sample.
- Mounting: Specimens were placed in the drawer-type test cells of the C303H. The system’s automatic clamping feature ensured a consistent sealing force across all cells.
- Parameter Setting: Using the 12-inch Windows touch panel, technicians set the test temperature (38°C) and relative humidity (90% RH) in accordance with standard tropical test conditions.
- Execution: The " one-click " automatic mode was initiated. The C303H monitored and adjusted flow, temperature, and humidity in real-time until the WVTR reached a stable state.
5. Results and Analysis
The test results, yielding the mean value of three specimens for each sample, are as follows:
Sample | Coating Thickness | WVTR Result [g/(m2·24h)] |
VMBOPP - A | 4.44μ | 0.463 |
VMBOPP - B | 5.2μ | 0.071 |
Observations: The data reveals that an increase in coating thickness from 4.44μ to 5.2μ resulted in a massive improvement in barrier performance. Specifically, a thickness increase of just 18% led to a nearly 85% reduction in water vapor transmission.
6. Conclusion
The thickness of the aluminized layer is a decisive factor in the barrier performance of aluminized films. This study demonstrates that even a small increase in aluminum deposition can significantly enhance moisture resistance, allowing manufacturers to tailor packaging to specific shelf-life requirements.
The Labthink C303H Test System proved to be an essential tool in this research. Its infrared sensor technology provides high sensitivity for low-barrier detection, while the three-cell design ensured data consistency & repeatability. For packaging manufacturers, the C303H offers a safe, reliable, and highly intelligent solution for mastering the barrier properties of new-generation materials. For more information, please visit https://en.labthink.com/.