PEN films

PEN Films Are Films with High Thermal Stability

Films made from polyethylene naphthalate are polyester films similar to PET films. However, unlike PET, their base material is not synthesized from dimethyl terephthalate and ethylene glycol, but from naphthalene-2,6-dicarboxylic acid combined with ethylene glycol.

The manufacturing process of polyethylene naphthalate is a polycondensation reaction. Due to the composition of this polyester, the film production results in chemical and mechanical properties that differ from those of other polyester films.

PEN films are therefore used in applications where higher heat resistance and very good resistance to water are required.

Chemical and Physical Properties of PEN Films

PEN films are characterized by higher thermal stability than PET films, which allows for a higher operating temperature. Higher tensile strength as well as lower elongation and shrinkage values are further differences compared to PET materials.

In the area of hydrolysis resistance, meaning resistance to water, PEN films also perform better than PET, as they do in their barrier performance against gases and moisture.

Their mechanical strength and chemical resistance are also very good. PEN films also achieve very good results in terms of UV resistance.

The only area in which PEN films show poorer performance than PET films is long-term flexural fatigue resistance.

Electrical Properties of PEN Films

PEN films have very good electrical properties and exhibit only low dielectric losses despite their high thermal stability. They are therefore suitable for applications such as capacitors or transformers, which place high demands on long-term stable electrical insulation properties.

In some of these applications, such as in the solar sector, the UV resistance of PEN films is also an important characteristic.

The Manufacturing Process of PEN Films

After the thermoplastic base material polyethylene naphthalate is produced through a polycondensation process, a film is extruded from it. Immediately after production, this film is biaxially stretched, meaning it is drawn in both the longitudinal and transverse directions.

This stretching process, which is also known from BO-PET film, gives PEN film its excellent mechanical and thermal properties.

Since all PEN films undergo this stretching process, the additional designation BO for biaxial orientation is usually omitted.

Modifications of PEN Films

The production of PEN films can be adapted to the specific requirements of the final material. Both copolymerization with other materials and surface treatments such as coatings or laminations are possible in order to modify the surface properties.

For example, PEN films can be equipped with antistatic, scratch-resistant, or optically optimized surfaces.

Application Examples in the Electrical and Electronics Sector

• Flexible printed circuit boards (FPCs)
• Solar cell backsheet films
• Insulation material in battery production
• Insulating material in electric motors and generators
• Displays in electronic devices

For Which Application Areas Outside Electrical Engineering Are PEN Films Suitable?

In the packaging sector, PEN films are used for chemically sensitive components. In the food industry, PEN films are suitable for packaging that must be UV-resistant and able to withstand higher temperatures than PET films.

Especially for sensitive products such as pharmaceuticals or easily perishable foods, PEN film is an ideal packaging material.

PEN is also used to produce labels, laminates, optical displays, and optical devices such as scintillators or polarization filters for cameras and LCD screens. In addition, fibers made from polyethylene naphthalate are produced, which are more tear-resistant than polyester or nylon.

In the field of medical technology, containers and medical devices are manufactured from this material.

In summary, PEN materials are used for demanding applications where films made from PET materials are no longer sufficient. Although PEN films are more expensive than PET films, they are still cheaper than polyimide films, which offer even better chemical and physical properties than PEN films.

Advantages of PEN Films Compared to Other Film Types

• PEN films outperform PET films in applications that require high thermal stability
• In certain areas of chemical resistance, PEN films are also superior to PET films
• PEN films are more UV-resistant than PET films and many other films
• In terms of electrical properties, PEN film exceeds most other film types
• PEN films offer a better cost-performance ratio compared to polyimide films, which are also suitable for high-temperature applications
• PEN films are easier to process than polyimide films

Disadvantages of PEN Films

• The production of PEN films is cost-intensive
• Due to their cost-performance ratio, PEN films are limited to a few specialized applications
• An established recycling system for PEN films does not yet exist, although they are technically recyclable

Sustainability of PEN Films

PEN films are produced from fossil-based raw materials. They are not compostable, and an officially established recycling process for this material does not yet exist.

As a positive sustainability aspect, it is often noted that these films are very durable and can contribute to extending the shelf life of products.

There are also research efforts aimed at finding alternatives to fossil raw materials for the production of polyethylene naphthalate. However, these approaches are still at the research stage, and it is not yet clear whether large-scale industrial use will be feasible and economically viable.

Efforts are also being made in the field of recycling to make PEN films usable again in manufacturing processes. The long-term improvement of the sustainability of PEN films will depend on the success of these research developments.