Hydrolysis-resistant BO-PET films

Hydrolysis-resistant BO-PET films for technical applications and other areas

For many film applications, hydrolysis resistance is an important requirement. For most applications in the packaging sector, protection against water and moisture is a decisive function that the packaging must fulfil. In many technical applications as well, especially in electrical engineering or electronics, protection against moisture-related corrosion or moisture-related malfunctions is an important aspect when selecting a film, in addition to the electrical properties. Hydrolysis-resistant BO-PET film is available in various thicknesses for different applications.

Characteristics of hydrolysis-resistant BO-PET films

PET films are made from the thermoplastic polymer polyethylene terephthalate. For hydrolysis-resistant BO-PET films, the films are stretched in two directions immediately after extrusion. This stretching, known in technical terminology as orientation, takes place in the longitudinal and transverse directions, which is why it is referred to as biaxial orientation. This is reflected in the term BO in the name of the films. Biaxial orientation is responsible for many of the important properties of BO-PET film. By changing the crystal structure, the film becomes temperature-resistant, tear-resistant and dimensionally stable. For good resistance to chemical reactions with water, hydrolysis-resistant BO-PET films are additionally treated.

Options for improving hydrolysis resistance

The hydrolysis resistance of BO-PET films can be improved in various ways. One option is copolymerization, in which other monomers are added to polyethylene terephthalate during the production process. The use of additives in the polymerization process is also a possible method for increasing the hydrolysis resistance of BO-PET films. Coatings are also used to improve the hydrolysis resistance of BO-PET films, as are heat treatments and plasma treatments.

Methods for improving the hydrolysis resistance of BO-PET films

• Copolymerization

Monomers such as isophthalic acid or cyclohexanedimethanol are introduced during polymerization. These monomers modify the regular structure of the polymer chains and make them less susceptible to attack by water.

• Additives

Stabilizers such as carbodiimides or epoxy-based additives can be added to PET during processing. Additives act as reaction partners for water and thus delay the degradation process.

• Silicone or epoxy coatings

Coatings create a water-repellent barrier.

• Nanocomposites

Silicon oxide or aluminium oxide can reinforce coatings as nanoparticles and provide an additional barrier.

• Heat treatment

After the film has been produced, heat treatment, also known as annealing, can increase crystallinity and thus further improve the resistance of BO-PET films to water and high temperatures.

• Plasma treatment

Plasma treatments can specifically modify the surface properties of films. The creation of a hydrophobic layer reduces the penetration of water into the film.

Applications of hydrolysis-resistant BO-PET films

• In electrical engineering, hydrolysis-resistant BO-PET films are used as insulation material in motors, transformers, generators or relays
• In electronics, hydrolysis-resistant BO-PET films are used for displays, printed circuits or circuit boards
• In the packaging of food, pharmaceutical products or other sensitive products that require protection against moisture, hydrolysis-resistant BO-PET films extend shelf life
• In the industrial sector, hydrolysis-resistant BO-PET films are used as carrier films for adhesive tapes
• In automotive engineering, hydrolysis-resistant BO-PET films are used in components and cable insulation that must withstand adverse environmental influences
• In the solar industry, hydrolysis-resistant BO-PET films serve as protective films for photovoltaic modules because they resist UV radiation, moisture and temperature fluctuations

Environmental friendliness of hydrolysis-resistant BO-PET films

In addition to their origin from fossil raw materials, some methods for improving the hydrolysis resistance of BO-PET films worsen the environmental balance of the films. Both copolymerization and the use of additives and coatings reduce the possibilities of introducing BO-PET films into the recycling cycle that is, in principle, well established for PET. Heat treatments and plasma treatments offer a more environmentally friendly alternative here because they do not prevent recycling. Research into other recycling processes that aim to break materials down into their basic components shows ways in which hydrolysis-resistant BO-PET films can be disposed of in a more environmentally friendly way in the future. In addition, research is also being carried out into more environmentally friendly substances that can be used for hydrolytic stabilization. Research into raw materials for BO-PET material derived from renewable resources also gives hope that hydrolysis-resistant BO-PET films can be produced in a more environmentally friendly way in the future.