Film production

The broad product range in film production

Films are products ranging from just a few µm in thickness to several millimetres. Plastic films in the millimetre range are so rigid that a layperson would no longer refer to them as film, but rather as a plastic sheet. However, since they hardly differ from thin films in the manufacturing process, thick films are also referred to as films in technical terminology. Plastic is not the only material from which films can be produced. Thin films can also be made from metals, the best-known example being aluminium film. In addition, it is possible to produce films from materials obtained from renewable raw materials. In the strict sense, these are not plastic films, but they are often referred to as such, for example as plastic film made from renewable raw materials or compostable film. This text takes a closer look at the production of plastic films and films made from renewable raw materials.

Film production and its market environment

The material development of film base materials and the formulation of films are important prerequisites for film production. Suitable raw materials are selected and combined with additives, auxiliary materials, other materials or colours. Various production processes are available for the manufacture of films. The most commonly used process is extrusion, but casting, blowing and calendering are also methods used for certain films. Film production alone is not enough; the purchasers of films from a wide range of industries must receive application-related advice from film manufacturers. Specific product characteristics, processing options, required certifications and environmental standards must be aligned with customer requirements for the films offered.

Finishing, further processing and certification of film products

Certain finishing steps such as printing, laminating, coating or embossing are often already offered as part of film production. Cutting to customer specifications or the supply of certain roll goods such as mother rolls or master rolls also falls within the scope of film production. Another important task in film production is quality assurance and certification in order to comply with legal requirements. Requirements from both the health sector and the environmental sector play a role here. Quality control also ensures that the product characteristics requested by the customer have been implemented in production.

Film production from petrochemical plastics

In film production, a broad range of films is manufactured from raw materials obtained from crude oil. Some important materials for film production include:

• Polyethylene (PE) is processed into films as LDPE, HDPE and LLDPE. The abbreviations stand for “low density” for LD, “high density” for HD and “linear low density” for LLD. LD means soft and flexible, HD rigid and strong. LLD is a mixed form of the other two qualities. The films are used, for example, for various types of packaging, bags for different applications or agricultural films.
• Polypropylene (PP) is used as biaxially oriented film (BO-PP) for labels, food packaging, non-food packaging and a wide range of other applications.
• Polyester (PET) is in many cases processed as BO-PET, also a biaxially oriented film. However, films are also produced from amorphous polyethylene terephthalate (A-PET) or glycol-modified PET (PET-G). BO-PET films are heat-resistant, dimensionally stable and mechanically very stable. They are suitable for many packaging solutions and technical applications. A-PET films are glass-clear and very easy to form.
• Polyamide (PA) is mainly used to improve the properties of other films as a component of a multilayer film. For example, mechanical strength and thermoformability are improved by PA. PA film serves as an aroma and gas barrier and gives vacuum packaging in particular high puncture resistance.
• Polyvinyl chloride (PVC) was one of the most commonly used plastics, but was then strongly pushed back due to the chlorine compounds it contains and has almost completely disappeared from applications in the food sector. Films made from PVC are transparent, stretchable and stable. In the construction or decoration sector, these durable films are still used for certain applications.
• Ethylene vinyl acetate (EVA) is a versatile film material that can be used in many areas. The material is particularly important as an interlayer film in laminated glass panes, where it prevents injuries caused by splinters, and for solar module encapsulation.

Film production from renewable raw materials

In film production, the increasing demand for films made from renewable raw materials must be met. Ideally, the films should also be compostable. Here are some examples:

• Polylactide (PLA) is a material produced from lactic acid and corn starch. It is also commonly referred to as polylactic acid. PLA film is food-safe and has a good moisture transmission rate. This property is particularly valuable for use in the food sector. Another argument in favour of PLA films is their compostability. They are also used in the non-food sector as transparent windows or for packaging in general.
• Diacetate film is made from wood fibres dissolved in acetone. The films are also compostable and impress in food packaging thanks to their good natural anti-fog effect. In addition to food packaging, diacetate films also play an important role in technical applications.
• Triacetate film, like diacetate film, is produced from wood fibres dissolved in dichloromethane. The film is used for special applications in the optical sector and other technical areas. Triacetate films are only compostable under controlled conditions.
• Cellulose hydrate is also produced from the raw material cellulose. The product produced is known as regenerated cellulose film or glassine paper, but is best known under the original brand name Cellophane. It is compostable, but can also be disposed of without problems through waste paper or thermally. In the packaging industry, this oldest film material was largely displaced in the 1950s by lower-cost petroleum-based films. Today, cellulose hydrate is once again gaining importance in film production because films made from natural raw materials are in demand for environmental reasons.

Importance of metallized films and composite films in film production

Films are equipped for specific applications by vapour deposition with aluminium, other metals or materials, as well as by laminating and coating. In film production, films with specific properties are also produced by combining different film materials through coextrusion. In this way, barrier properties, for example, are adapted to the intended use of the films. The protection of products against oxygen and other gases, light, UV radiation and moisture can be specifically modified with the additional layers of a multilayer film. In film production, the complex interaction of a wide range of film materials, additives and other coating materials must be taken into account.

Special quality and safety requirements in film production

In film production, strict legal requirements must be observed and high customer quality requirements must be implemented. Especially when films are used in sensitive areas, such as food packaging or medical technology, there are many defined framework conditions. Important areas include, for example:

• For films used in the food sector, the strict requirements of EU Regulation 10/2011 apply in Europe. Similar FDA regulations exist for the US market. These regulations define the requirements that a film used in the food sector must meet.
• Compliance with these rules includes standardized migration tests that demonstrate which substances transfer from a film to another material. Film manufacturers must confirm these tests by means of a declaration of conformity.
• Film production also includes comprehensive documentation on barrier properties against oxygen, other gases and water vapour, as well as light and UV radiation.
• Tests on mechanical properties such as tear and puncture resistance, temperature resistance, elongation and dimensional stability must be carried out during film production and presented in product data sheets.
• Properties such as gloss, transparency, other optical properties or printability are important product characteristics in film production.
• The electrical properties of different films play an important role in technical applications.
• Sustainability, compostability and recyclability of film materials are becoming increasingly important. Certifications for environmental management such as ISO 14001 or for supply chain transparency such as ISCC PLUS are therefore becoming prerequisites for success on the market.

In film production, smart packaging means that films are offered which are able to take on additional functions. As with other “smart” solutions, such as in the smart home, smart packaging also connects the physical and digital worlds. Smart packaging opens up a bridging function in which communication takes place between manufacturers, retailers and consumers, with the possibility of including social media channels in this communication.

Film production of “active” packaging

In smart packaging, a distinction is made between active and intelligent packaging. In active packaging, film production integrates functions that are capable of interacting with the packaged product. This can include, for example, the absorption of gases such as oxygen or ethylene. Light-filtering properties of films are also counted among these active properties. Antimicrobial and moisture-regulating films ensure longer product shelf life in food packaging and sterility in medical technology packaging. For all these properties, special materials, additives or coatings have been developed in film production.

Film production of “intelligent” packaging

In intelligent packaging, diagnostic and indicator functions are integrated into the films during film production. Intelligent packaging has properties, for example, that can provide information about the condition of the packaged product. This can be used to assess the product or for documentation purposes. Indicators or sensors integrated into the films provide the relevant information. Information on temperature or tightness, storage time or freshness of the packaged products can therefore be read directly from the packaging. Motion-sensitive sensor systems are also possible, documenting shocks or other movements such as rotation. Many intelligent functions serve to simplify and accelerate storage, logistics and documentation. The higher price of intelligent packaging can pay off in the long term through savings in these areas.

Augmented reality elements in film production

Augmented reality elements in intelligent packaging expand the product experience digitally. In most cases, additional information is provided after scanning with a smartphone or tablet, or entertaining content related to the packaged product is offered. Augmented reality in film production therefore enables completely new marketing functions in which products are virtually enhanced via smartphone. This ranges from easily accessible product information and supply chain information through to dedicated digital experience worlds around the intelligently packaged product. There are hardly any limits to the ideas of marketing departments here. One click can lead to a competition, a recipe matching the product or the sustainability concept of the producing company.

Disposal of smart packaging products

One of the greatest challenges in the field of smart packaging is the issue of disposal. Due to the electronic elements they contain, packaging with independent electronic functions falls under the scope of electrical and electronic equipment legislation. In disposal, they must therefore be treated like electronic devices. Disposal with household waste is therefore not possible. Manufacturers must create special disposal options for their packaging or label it as hazardous waste, which is not desirable. In order to make extensive use of the possibilities offered by smart packaging, all parties involved in film production and packaging design are required to develop solutions that enable the use of smart product packaging in compliance with legal requirements.

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