The lamination process of the handheld pure aluminum spout bag is a key factor in determining its barrier properties. Through the scientific combination and precise lamination of multiple layers of materials, it significantly enhances its barrier properties against oxygen, water vapor, and light, thereby extending the shelf life of the contents and maintaining consistent quality. This process involves three key dimensions: material selection, interlayer structure design, and lamination technology, all of which directly impact the barrier properties of the final product.
In terms of material selection, the handheld pure aluminum spout bag typically utilizes a three-layer composite structure: outer layer, middle layer, and inner layer. The outer layer is typically made of high-strength materials such as PET or PA, providing puncture resistance and printability. The middle layer, with pure aluminum foil as its core, leverages its dense metallic crystal structure to create a barrier. The inner layer utilizes heat-sealable materials such as PE or CPP to ensure sealing and chemical resistance. The addition of aluminum foil is crucial, as its oxygen transmission rate can be reduced to below 0.1 cm³/(m²·24h) and its water vapor transmission rate to less than 0.5 g/(m²·24h), far exceeding the barrier properties of pure plastic materials.
The interlayer structure design must balance functional complementarity and process feasibility. The aluminum foil layer must adhere tightly to the adjacent materials to avoid barrier failure due to interlayer gaps. For example, in the lamination of aluminum foil and PET, coextrusion or adhesives are necessary to enhance interfacial bonding and prevent oxygen permeation between the layers. Furthermore, the thickness and surface treatment of the aluminum foil also affect barrier properties. Excessively thin aluminum foil may develop pinholes due to mechanical damage, while surface coating with aluminum oxide or organic coatings can improve corrosion resistance and flexibility.
Temperature and pressure control during the lamination process are key technical aspects. Dry lamination uses heated, melted adhesive to achieve interlayer bonding, requiring precise temperature control to prevent overheating and deformation of the aluminum foil. Coextrusion lamination utilizes a multi-layer extrusion die to simultaneously form each layer while molten, minimizing interlayer defects. Improper process parameters, such as excessively high temperatures or insufficient pressure, can cause the aluminum foil layer to delaminate from the heat-seal layer, creating barrier vulnerabilities.
The integrity of the aluminum foil layer directly impacts barrier performance. During the lamination process, aluminum foil may develop micropores due to mechanical winding, improper tension control, or friction with rigid materials. Although invisible to the naked eye, these micropores can serve as permeation channels for oxygen and water vapor. Therefore, post-lamination inline inspection, such as corona testing or high-voltage discharge testing, is necessary to promptly remove defective products.
The impact of the heat-sealing process on barrier properties is often overlooked. The spout of the handheld pure aluminum spout bag requires heat sealing. Excessive heat sealing temperatures or prolonged sealing times can lead to excessive fusion between the aluminum foil and the heat-sealing layer, compromising the barrier structure. Insufficient heat sealing can cause leakage. Therefore, heat-sealing parameters must be optimized for different material combinations to ensure a balance between sealing and barrier properties.
Lamination with other materials can further enhance the overall performance of the handheld pure aluminum spout bag. For example, adding VMPET (aluminized PET) between the aluminum foil layer and the inner PE layer can enhance UV reflectivity, preventing the contents from photooxidation. Alternatively, a nylon (PA) layer can be added to improve puncture resistance, adapting to the packaging needs of sharp items. This multi-layer composite structure achieves a balance of barrier properties, mechanical strength, and aesthetics through functional integration.
In practical applications, the lamination process for the hand-held pure aluminum spout bag must be customized based on the characteristics of the contents. For example, when packaging easily oxidizable foods like coffee, the oxygen barrier properties of the aluminum foil layer must be enhanced; while when packaging liquid products, the sealing process at the spout must be optimized. Through continuous improvement of the lamination process, the hand-held pure aluminum spout bag is becoming the preferred solution for high-barrier packaging, providing more reliable quality assurance for industries such as food, pharmaceuticals, and cosmetics.
