Why can high-barrier aluminized PET film effectively block water vapor?

In the selection of packaging materials, moisture-proof performance is a key indicator that many industries pay close attention to. For products such as milk powder and tea that are extremely sensitive to humidity, a packaging material that can effectively block the intrusion of external moisture is the core element to ensure product quality. High-barrier aluminized PET film has emerged in the packaging field with its excellent water vapor barrier performance and has become an ideal choice for moisture-proofing of many products.

High-barrier aluminized PET film is a composite material with strict process requirements in its preparation process. PET (polyethylene terephthalate) as the base layer of the film itself has certain physical performance advantages. PET is a thermoplastic polyester with good mechanical strength, which makes the film not easy to break during use and can provide a solid support foundation for the aluminized layer. At the same time, PET also has good chemical stability and is not easy to react chemically with other substances under normal conditions, ensuring the stability of the overall performance of the film.

The thin layer of aluminum atoms deposited on the surface of the PET film through the vacuum aluminum plating process has become the key to the film's high barrier performance. In a vacuum environment, aluminum atoms can be evenly deposited on the surface of the PET film to form a dense aluminum layer. Although the thickness of this aluminum layer is thin, it plays a vital role in water vapor barrier.

From a microscopic perspective, the diameter of a water molecule is usually between 0.28 and 0.4 nanometers, while the aluminum layer structure of the high-barrier aluminum-plated PET film is extremely dense, and its pore size is much smaller than the diameter of a water molecule. When external water vapor tries to penetrate the film into the interior, the aluminum layer is like a solid barrier, and it is difficult for water molecules to penetrate through the pores of the aluminum layer. At the same time, the aluminum element itself is oxygen-philic. In the natural environment, a very thin aluminum oxide protective film will form on the surface of the aluminum layer. This protective film further enhances the stability and barrier properties of the aluminum layer. It is not only difficult for water molecules to pass through the pores of the aluminum layer, but also difficult to react chemically with the aluminum layer and penetrate into the interior of the film.

Milk powder products are rich in various nutrients such as protein, fat, carbohydrates, etc. These ingredients can maintain good physical and chemical properties under suitable humidity conditions. Once milk powder absorbs too much water, its internal protein and other ingredients are prone to denaturation, resulting in milk powder agglomeration. The agglomerated milk powder not only has poor dissolution properties, but may also accelerate deterioration due to the growth of microorganisms, seriously affecting the quality and food safety of milk powder. High-barrier aluminized PET film can completely isolate milk powder from the external humid environment. Whether in the storage link after production or in the sales process, it can ensure that the milk powder is always in a dry state and maintain its nutritional content and taste stability.

Tea is also a product that is highly sensitive to humidity. Tea contains tea polyphenols, caffeine, amino acids and other flavor substances. These substances can slowly oxidize in a dry environment to form the unique flavor and aroma of tea. However, when tea leaves are damp, the chemical reaction inside them will accelerate, resulting in excessive oxidation of tea polyphenols and other substances, the loss of tea aroma, and the taste will become bitter. The moisture-proof performance of high-barrier aluminized PET film can create a relatively dry and stable storage environment for tea, slow down the oxidation rate of the internal components of tea, keep the original flavor and color of tea for a long time, and let consumers taste the purest taste of tea when brewing.

Under different environmental humidity conditions, high-barrier aluminized PET film can maintain stable water vapor barrier performance. Whether in the humid rainy season in the south, where the ambient humidity may be as high as 80% or above, or in the dry but occasionally fluctuating humidity environment in the north, the film can effectively play a moisture-proof role. Its extremely low water vapor permeability keeps the humidity inside the package within a range suitable for product storage, providing reliable guarantee for product quality and shelf life.

With its unique structure and performance, high-barrier aluminized PET film has demonstrated excellent ability in water vapor barrier, providing high-quality packaging solutions for humidity-sensitive products such as milk powder and tea. With the continuous advancement of science and technology and the increasing requirements for the performance of packaging materials, high-barrier aluminized PET film is expected to be used in more fields and play a greater role in product quality assurance and market circulation.