The three-layer blown film extrusion process is an important technology in modern plastic film production. It can not only effectively improve the overall performance of the film, but also flexibly adjust the structure and function of the film according to different needs. This process is widely used in food packaging, agricultural film, pharmaceutical packaging and other fields. It is favored by various industries because of its significant protective effect and excellent physical properties.

3 layer co-extrusion ABA blown film machine SEP-ABA/45+55mm

Introduction to three-layer blown film extrusion process

The three-layer blown film extrusion process uses co-extrusion technology to extrude three different plastic resins through a single die at the same time to form a multi-layer plastic film. Compared with single-layer membranes, the biggest advantage of three-layer membranes is that it can combine the advantages of different materials to achieve higher overall performance. The three-layer structure can not only effectively improve the mechanical properties of the film, such as tensile strength and puncture resistance, but also give the film other special functions, such as moisture resistance, UV resistance, oxygen and moisture barrier, etc.

Each layer of material in the three-layer membrane has a different function. The outer layer usually uses materials with strong weather resistance and UV resistance to cope with changes in the external environment; the middle layer often chooses materials with strong barrier properties to protect food or products; while the inner layer needs to have better Sealing performance ensures product safety and freshness. Therefore, through reasonable design and material selection, three-layer blown film can meet the needs of different industries.

Detailed process of two- and three-layer blown film extrusion process
Although the three-layer blown film extrusion process seems complicated, it actually contains several key steps, and each link requires precise control to ensure the quality of the final film.

Raw material preparation and feeding
The production of three-layer blown film first requires the selection of suitable plastic resin as raw material. Commonly used materials include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polypropylene (PP), etc. The selection of these materials usually depends on the use requirements of the film. The outer material needs to be UV-resistant and anti-aging, while the inner layer focuses on sealing and resistance to penetration. Before production, raw materials usually need to be dried to avoid excessive moisture affecting the quality of the film.

Plastic melting and extrusion
Next, the heated and molten plastic is fed through an extruder into a die. In a three-layer co-extrusion die, three different plastic materials are extruded simultaneously and merged through the die to form a three-layer structure. The thickness and composition of each layer can be adjusted according to needs. In order to ensure proper fluidity and temperature control of the melt, the operation of the extruder needs to be very precise to avoid problems such as uneven melt and excessively high or low temperature, which will affect the quality of the film.

Co-extrusion and blow molding
After the die stacks three different molten plastics together to form a film tube, the film then enters the blow molding process. The film tube is inflated to the required size through an air blowing system. At this time, the film is blown out of the die by air flow, gradually expanded and cooled. Temperature control in this process is crucial. If the temperature is too high, the film may deform or bubbles may appear; if the temperature is too low, the film may have insufficient toughness.

Cooling and shaping
The film enters the cooling system after blow molding. Cooling usually uses water cooling or air cooling to quickly cool down and shape the film. The cooling speed must be moderate. Too fast cooling may cause wrinkles or shrinkage on the film surface, and too slow cooling may affect production efficiency. The cooled film is further stabilized in size through stretching rollers and shaping rollers to ensure uniform thickness and stable structure of the film.

Rewind
Finally, the cooled and shaped three-layer film will be rolled into a film roll through a winding device. Tension needs to be controlled during the winding process to avoid wrinkling or cracking of the film during winding. Fine winding not only ensures the neat appearance of the film, but also ensures smooth use during subsequent processing.

Advantages of three-layer blown film extrusion process

Improve film performance
The biggest advantage of the three-layer blown film extrusion process is that the function of each layer can be adjusted according to the needs of the product. For example, the outer layer can use anti-ultraviolet and anti-aging materials to ensure that the film is not easily damaged outdoors or in a long-term exposure environment; the middle layer can choose materials with high barrier properties, such as anti-oxidation and anti-water vapor permeability materials. , to ensure the quality of the product; for the inner layer, materials with better sealing and adhesion can be selected to improve the protective properties of the film.

Save materials and costs
In traditional single-layer film production, expensive high-performance materials may need to be used, but through the three-layer blown film process, the use of expensive materials can be reduced while maintaining film performance. For example, the inner layer uses lower-cost plastic materials and the outer layer uses high-performance resin. This design greatly reduces production costs.

Versatility
By adjusting the composition and thickness of each layer, three-layer blown film can integrate multiple functions into a single film. For example, properties such as waterproof, oil-proof, UV resistance, antioxidant, and tear resistance can all be achieved through reasonable formula design. This versatility makes three-layer blown film widely used in multiple industries.

Environmental protection and sustainability
As environmental regulations become increasingly stringent, the environmental protection of the three-layer blown film process has also become an important consideration. Today, more and more three-layer blown films use degradable or environmentally friendly materials, reducing the environmental burden of packaging materials. For example, the use of biodegradable materials such as PLA (polylactic acid) not only meets market demand, but also promotes the process of sustainable development.

Application fields of three-layer blown film extrusion process

food packaging
Food packaging has very high requirements for films, especially the ability to prevent moisture, preserve freshness, and block oxygen and moisture. Three-layer blown film is widely used in the field of food packaging due to its excellent barrier properties and sealing properties, especially for the protection of perishable food. For example, three-layer film can effectively extend the shelf life of dried fruits, quick-frozen foods, and fresh fruits and vegetables.

agricultural film
Agricultural films are used in greenhouses, plastic greenhouses and other places. Their main functions are thermal insulation, waterproofing and light transmission. Three-layer blown film can provide the required thermal insulation effect and UV resistance according to different seasons and climate conditions, effectively promote plant growth and extend the service life of the film.

Pharmaceutical packaging
The pharmaceutical industry has extremely high requirements on the hygiene and sealing properties of packaging materials. The inner layer of the three-layer blown film can be made of materials that meet food-grade standards to ensure the safety and long shelf life of the medicine. The outer layer can be designed with antibacterial and anti-pollution functions to ensure that the quality of the medicine is not affected by the external environment.

industrial use
In some industrial fields, three-layer blown film is not only used for packaging, but also as protective film, isolation film and other applications. For example, the packaging of certain precision equipment requires films with high puncture resistance, stretch resistance and corrosion resistance. Three-layer blown film can exactly meet these needs.

The three-layer blown film extrusion process has become one of the indispensable production processes in various industries due to its excellent versatility and high cost performance. Whether in food packaging, agricultural film, medical packaging, or industrial applications, three-layer blown film has shown great advantages. With the continuous advancement of science and technology and the promotion of environmental protection concepts, the three-layer blown film process will continue to develop in the future, bringing more innovative solutions.