When referring to a functional composite film, the term “multi-layer co-extruded barrier film” is used to describe a film that is produced by employing multiple extruders to extrude resin that possesses higher barrier qualities and melts of other resins through a common die.

A plastic film is what we mean when we talk about multi-layer coextruded barrier film. Flat plastic products with a thickness of less than 0.2 millimetres are typically referred to as plastic films in the field of plastic products. Plastic sheets are used to refer to plastic products with a thickness between 0.2 and 0.7 millimetres, while plastic sheets are used to refer to plastic products with a thickness larger than 0.7 cm. Plating.

There are specific gas barrier qualities that should be present in multilayer coextruded barrier films. In this context, the term “barrier property” refers to the capacity of plastic items (such as containers and films) to act as a defence mechanism against odours and small molecular gases. When we measure the barrier qualities of plastic items, we typically utilise the gas gearbox rate as our standard.

When it comes to gas barrier qualities, general polymers like PE and PP have higher gas permeability ratings, which indicates that they are not very effective. Nevertheless, resin materials such as PA, PVDC, EVOH, and other resin materials have gas permeability values that are significantly lower than those of common plastics and have features that are superior to those of plastics. For this reason, we typically refer to multi-layer co-extruded barrier films as multi-layer co-extruded films. These films comprise at least one resin material, and they can be composed of PA, PVDC, or EVOH.

The vacuum packaging of dairy goods, jam, meat products and other products can be accomplished by the use of multi-layer co-extrusion of PE, PA, TIE and EVOH, among other resins.

When it comes to multi-layer co-extruded films, the most common structure is an ABCBA 5-layer symmetrical structure. The barrier layer is typically made of PA or EVOH, while the heat sealing layer is typically made of polyethylene. In order to accomplish the separation of the unconnected barrier and heat seal layers, adhesive resin is utilised. When it comes to resins, PA or EVOH are highly sensitive to the presence of humidity. They are shielded from the elements by a layer of polyethylene, and their remarkable oxygen barrier capabilities are utilised to their utmost potential.

The structural requirements of a multilayer coextruded film are the primary factor that determines the structure of the film in a broad sense. Assuming that the process requirements are satisfied, it is possible to fulfil the functional requirements of packaging materials by combining various polymers. These functional requirements include the ability to provide a barrier, heat sealing, body strength, thermal puncture resistance, environmental suitability, secondary processing characteristics, extended storage, and shelf life. After conducting an analysis of the functional requirements, it was determined that a mixture of five polymers is enough.

On the other hand, co-extruded composite films with seven, nine, eleven, or even more layers have started to be employed in the market, which has resulted in the phenomenon becoming a trend and fast increasing. The structural design of co-extruded films is gradually required in order to systematically reach the optimal state of integrating features such as function, technology, cost, environmental protection, safety, and secondary processing.

In light of this, what are the advantages of the structural properties of a multi-layer co-extruded film that is divided into the barrier layer and the heat sealing layer, and then joined through further functional divisions? In order to illustrate the differences between a 5-layer co-extruded film and a 7-layer co-extruded film, the following analysis will be performed:

1. a comparison of the costs

It is possible to minimise the cost of the product by replacing pricey polymers on the surface layer with cheaper polymers. This provides the product with the heat sealing properties and strong moisture barrier properties that are associated with ionic polymers. Comparatively, a seven-layer co-extruded blown film is more cost-effective than a five-layer one when it comes to materials that have the same barrier characteristics and heat sealability.

Both of the surface layers are separated into two groups, with one of the groups consisting of materials that are inexpensive. Not only does this help to preserve the quality of the film, but it also helps to reduce expenses. Take, for instance, two films that weigh 1 kilogramme each. When compared to the cost of manufacturing a 7-layer film, the material cost of a 5-layer film is 19% greater. It is possible for the cost of a 5-layer co-extruded film to be comparable to that of a 7-layer film product if inexpensive EVA is used to replace the ionomer polymer in the film. On the other hand, the difficulty is that the heat sealing strength is not substantial enough.

2. qualities that act as barriers

Rather than using a single polymer on the barrier layer, it is possible to significantly improve its barrier qualities by using two distinct polymers simultaneously. For instance, combining an EVOH layer with a typical nylon material can not only keep the penetration resistance of PA intact, but it can also increase the strength of EVOH and improve the crack resistance of EVOH. This is because the EVOH layer is sandwiched between two layers of PA amine, which results in the formation of a film with high barrier properties. This is something that cannot be accomplished with 5-layer co-extruded films.

There is the possibility that the total consumption of the structure will be raised due to the additional expense of adding EVOH. Under the same conditions, the oxygen transmittance of a 7-layer film is 0.13 units when EVOH is added to the film, whereas the oxygen transmittance of a 5-layer coextruded film with a 20% PA structure is 3.5 units.

The resistance to cracking

By utilising co-extruded films with a greater number of layers, it is possible to enhance the performance of PA co-extruded films that had fewer than five layers. By way of illustration, the utilisation of an additional adhesive layer has the potential to enhance the barrier qualities of a film by augmenting its water vapour barrier. In addition, the film may be made to be softer, it has a pleasant feel, and it has excellent anti-cracking capabilities. This is an additional advantage that can be acquired simultaneously.
As a result of the ongoing development of technology for the synthesis of polymers, new polymers that possess distinctive mechanical and physical properties are becoming increasingly effective in satisfying the requirements for packaging. There will be an increase in both the flexibility and the economy of the multi-layer co-extruded composite substrate film’s function and structure. Through the implementation and enhancement of moulding equipment and processes, in conjunction with the one-of-a-kind and efficient design of composite structures, film manufacturers will revolutionise their pursuit and thinking of concepts such as diversifying the functions of packaging, rationalising the structures of packaging, and maximising the benefits of packaging. function.

On the other hand, the scientific utilisation of raw materials, the creation of an acceptable product structure, and the close collaboration with processing technology are all challenges that each of our composite film manufacturers must face. As a result of the fact that the packaging base material can only be utilised in the most cost-effective, reasonable, and adequate manner on its final product when the technical resources of processing equipment, processing raw materials, and structural design (processing technology) are fully utilised and reached the best state, the cheapest form appears and satisfies the requirements of the market.