Features of Multilayer Coextruded Barrier Films.

Mar 03, 2025

Multilayer co-extruded barrier films are generally produced using a multilayer co-extrusion blow molding process or casting process, a film molding technology, multilayer co-extrusion has excellent barrier properties, mechanical properties, stretch molding properties and heat sealing properties, and the processing does not need to add composite, and does not involve the printing of inks, adhesives and additives residues and other issues, so it is a relatively green and environmentally friendly, cost advantageous food packaging Technical process.

Multi-layer co-extruded barrier film refers to the use of more than three extruders, the different functions of resin raw materials, such as: polyethylene, polypropylene, nylon, ethylene-vinyl alcohol copolymer, etc., the distribution of melt extrusion, through their respective runners in the multi-layer co-extruded die at the head of the confluence, and then through the blowing and expanding or casting molding, and cooled after the composite together to form a multi-layer co-extruded film. By combining and designing the advantages of different resins, it is possible to produce films with comprehensive performance to meet various packaging needs.

Features of Multilayer Coextruded Barrier Films

-Combine the benefits of multiple materials

Multilayer coextruded barrier film structures offer a wide range of properties at the same time, thanks to the ability to combine materials with different properties as needed. For example, for heat-sealing and packaging machines that require films with good machinability, MDPE or HDPE materials are used in the multilayer structure to improve the strength and stiffness of the film and ensure good machinability, while metallocene (HAO) polyethylene materials with good heat-sealing properties are used in the inner layer to provide good heat-sealing and mechanical properties of the film and better meet the needs of packaging. The inner layer is made of polyethylene metallocene (HAO) with good heat seal performance, so that the film has good heat seal performance and mechanical properties to better meet the needs of packaging, and in order to meet the needs of different barrier, we can choose PA, EVOH, PVDC and so on to meet the different barrier needs of the film.

-Cost Control

Multi-layer co-extruded barrier film technology for multi-layer co-extrusion molding process, without the traditional composite, coating and other post-processing processes, can effectively reduce the cost of raw materials and production processes, not only to save production costs, but also in the film thickness control to achieve the feasibility of thinning.

- Customizable film structure upon request

The production of a variety of film structures, suitable for different packaging needs, through the structural design of a variety of materials in different combinations, give full play to the characteristics of different raw materials, but also according to the needs of different packaging applications, the design of different structural layers. And the more co-extruded layers, the greater the flexibility of the structure can be designed, on the market has been applied to the multi-layer co-extruded film structure has reached a maximum of 11 layers.

Due to the flexible design of multi-layer coextruded structure, it is possible to process high barrier films, medium barrier films and low barrier films. Different colors of barrier films can also be produced depending on the color masterbatch.

-Wide range of applications

Multi-layer coextruded film materials are suitable for all flexible packaging applications. Including food, daily chemicals, beverages, pharmaceuticals, electronic products, protective films and so on.
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Structural Design of Multilayer Coextruded Films

The structure of multilayer coextruded films can be divided into two categories, namely symmetric structure (A/B/A) and asymmetric structure (A/B/C). At present, China's barrier films are mainly 5-layer, 7-layer, 8-layer and 9-layer (some foreign companies do 10-layer and 11-layer). Take 5-layer coextruded film as an example to introduce the corresponding structure.

The structure of multilayer coextruded films can be divided into two categories, namely symmetric structure (A/B/A) and asymmetric structure (A/B/C). At present, China's barrier films are mainly 5-layer, 7-layer, 8-layer and 9-layer (some foreign companies do 10-layer and 11-layer). Take 5-layer coextruded film as an example to introduce the corresponding structure.

Barrier layer: The barrier layer has the functions of oxygen barrier, moisture barrier, prevention of oil leakage and permeability, etc. By controlling the barrier layer material and thickness, the barrier performance of the film material can be adjusted to meet different packaging requirements (commonly used barrier materials in the market include PA, EVOH, PVDC, etc.). Different barrier materials can be applied individually to form a series of high barrier and medium barrier packaging films, while the sandwich structure formed by the combination of PA and EVOH has high barrier performance.

Base layer: Generally, symmetrical structural materials have two base layers, the inner layer is used for heat sealing, called heat sealing layer, the outer layer is directly used as the outer layer of the packaging film or used for printing to become the printing layer. The base layer must have good mechanical strength, heat sealing performance, water vapor barrier and transparency and printability. This layer of commonly used materials for LDPE or LDPE / LLDPE blended material combinations are more.

Bonding layer: the role of the bonding layer to bond the barrier layer and the base layer to ensure that the interlayer peeling force, the selection of bonding layer materials and thickness is generally based on the materials of the base layer and the barrier layer as well as the need to achieve the bonding strength of the bonding layer to decide the bonding layer of the bonding agent used in the material.

At present, China's common structure and 7-layer, 8-layer, 9-layer barrier film, now PE \ PP on behalf of the base layer materials, PA on behalf of the barrier layer materials, multilayer co-extruded film structure description.

Symmetrically Structured Barrie Films
PE/Tie/PA/Tie/PE	Multi-layer co-extruded film equipment with five or more layers
PE/Tie/EVOH/Tie/PE	Multi-layer co-extruded film equipment with five or more layers
PE/Tie/PA/EVOH/PA/Tie/PE	Multi-layer co-extruded film equipment with seven or more layers

 

Asymmetric Structured Barrier Films
PA/Tie/PE/Tie/PA/Tie/PE	Multi-layer co-extruded film equipment with seven or more layers
PA/Tie/PP/Tie/PA/Tie/PP	Multi-layer co-extruded film equipment with seven or more layers
PA/Tie/PE/Tie/PA/EVOH/PA/Tie/PE	Multi-layer co-extruded film equipment with nine or more layers
PA/Tie/PP/Tie/PA/EVOH/PA/Tie/PP	Multi-layer co-extruded film equipment with nine or more layers

From the above structure can be seen, nine and more layers of co-extruded film structure has great flexibility, but the more layers, the greater the difficulty of the process, so the domestic multi-layer co-extruded film is generally controlled in the majority of 5-9 layers.

Development of multilayer coextruded films

In recent years, with the continuous improvement of plastic packaging film performance requirements, multi-layer co-extruded barrier film technology has been well developed, and it is believed that in the future, multi-layer co-extruded barrier film will be developed into a more multi-layer structure, and from the field of barrier packaging to the development of more areas.