What are the production processes for AL/PET composite films?

 

Principle: Dry lamination is the process of combining AL (aluminum foil) and PET (polyethylene terephthalate) materials through adhesive in a dry state. Firstly, apply a layer of adhesive on the surface of aluminum foil and PET film respectively, then dry them in a drying oven to evaporate the solvent in the adhesive, and finally bond the two layers of materials together under certain pressure and temperature.

Adhesive selection: Commonly used adhesives include polyurethane adhesives. This adhesive has good bonding properties and can firmly bond AL and PET together. For example, in the production of AL/PET composite films for food packaging, it is necessary to choose polyurethane adhesives that meet food safety standards to ensure the safety of the packaging.

Process advantages: Dry composite process can accurately control the coating amount of adhesive, thereby achieving good bonding effect. Moreover, it is suitable for composite of various thin film materials with different properties, and can produce composite films with high strength and barrier properties. For example, in the field of pharmaceutical packaging, AL/PET composite films produced through dry composite processes can effectively block oxygen and water vapor, ensuring the quality of drugs.

Process disadvantage: This process requires the use of a large amount of organic solvents as diluents for adhesives, such as ethyl acetate. These organic solvents evaporate during the drying process, which not only causes environmental pollution but also poses safety hazards such as flammability and explosiveness. Moreover, the drying process requires a significant amount of energy consumption.

 

 

Principle: Extrusion compounding is the process of using PET film as the base film and extruding molten plastic (such as polyethylene) through an extruder to evenly coat between the PET film and aluminum foil, thereby compounding AL and PET together. The specific process is to first add plastic raw materials into the hopper of the extruder. Under high temperature and the extrusion effect of the screw, the plastic becomes molten. Then, it is extruded through the die and bonded with PET and AL under pressure and cooling.

Plastic selection: In extrusion compounding, commonly used plastics include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), etc. These plastics have good flexibility and bonding properties. For example, in the production of AL/PET composite films for packaging of some daily chemical products that require high flexibility, the use of LLDPE can make the composite film have better hand feel and tear resistance.

Process advantages: The extrusion composite process has high production efficiency and can achieve continuous production. Meanwhile, it does not require the use of large amounts of organic solvents, making it relatively more environmentally friendly. In terms of cost, due to the reduction in the use of organic solvents and drying processes, production costs have also been lowered. For example, in some mass-produced ordinary packaging AL/PET composite films, extrusion composite technology is an economically efficient choice.

Process disadvantages: This process requires high equipment requirements, such as high-performance extruders and supporting cooling devices. Moreover, when laminating films with extremely high barrier performance requirements, such as AL/PET composite films for food preservation packaging with extremely low oxygen permeability requirements, simple extrusion lamination may not achieve the desired barrier effect and needs to be combined with other processes.

 

 

Principle: Co extrusion composite is the process of simultaneously extruding AL, PET, and other possible plastic materials through multiple extruders, and merging them together in a mold to form a composite film. This process involves directly compounding multiple materials in a molten state, without the need for adhesives like dry lamination or step-by-step steps like extrusion lamination.

Material combination: For example, PET and a plastic with special functions (such as ethylene vinyl alcohol copolymer EVOH, used to enhance barrier properties) can be co extruded and compounded with AL. By adjusting the parameters of each extruder, such as temperature, pressure, and extrusion speed, it is possible to evenly distribute different materials in the composite film and leverage their respective advantages.

Process advantages: The composite film produced by co extrusion composite process has strong adhesion between the layers, as it is composite in a molten state without obvious interfaces. Meanwhile, this process can precisely control the thickness and properties of each layer of materials, producing composite films with multiple functions. For example, in the high-end food packaging field, AL/PET composite films with high barrier and puncture resistance properties can be produced through co extrusion composite technology.

Process disadvantages: The co extrusion composite process requires multiple extruders to work together, and the equipment investment is relatively large. Moreover, the process control is relatively complex, requiring precise adjustment of the parameters of each extruder, and demanding high technical proficiency from the operators.