BO-PET barrier films

Secure packaging with BO-PET barrier films

Films with strong barrier properties against gases, moisture, and aromas are essential in the packaging industry for the safe protection of sensitive goods. BO-PET barrier films are based on biaxially oriented polyethylene terephthalate. In addition to excellent barrier performance, they offer dimensional stability, high mechanical strength, good resistance to various chemicals, oils, and greases, as well as high temperature resistance.

The production of BO-PET barrier films

Polyethylene terephthalate is a polyester produced from ethylene glycol and terephthalic acid through polycondensation. Film is manufactured from polyethylene terephthalate by extrusion. If this film undergoes a stretching process after production, its physical properties change. There are monoaxially stretched films and biaxially stretched films, meaning films stretched in two directions – longitudinally and transversely to the machine direction. The biaxial orientation of the latter is responsible for the “BO” in BO-PET film. The stretching process significantly enhances key properties of the polyester film, including its barrier performance.

Properties of BO-PET barrier films

• Barrier properties

BO-PET barrier films provide protection against oxygen, moisture, and aroma loss, making them ideal for packaging perishable goods.

• Mechanical strength

The biaxial orientation ensures excellent tear resistance, scratch resistance, tensile strength, and overall robustness.

• Thermal resistance

Resistance to both low and high temperatures is improved through biaxial stretching. BO-PET barrier films can withstand temperatures ranging from minus 70°C to plus 150°C.

• Chemical resistance

Their resistance to various chemicals makes BO-PET barrier films suitable not only for packaging but also for numerous technical applications.

• Dimensional stability

For many applications, the excellent dimensional stability of biaxially stretched PET films is a key advantage.

Enhancing the barrier performance of BO-PET films

There are several ways to further improve the already strong barrier properties of BO-PET films:

• Aluminum coating provides excellent protection against oxygen, moisture, and light, including UV radiation.
• Silicon oxide (SiOx) and aluminum oxide (AlOx) coatings create a transparent barrier with protection comparable to aluminum while maintaining product visibility.
• Acrylic or PVdC coatings, known as polymer barrier coatings, enhance gas and moisture barriers in applications that do not require metallic layers.

Applications of BO-PET barrier films

In the packaging industry, BO-PET barrier films are used for perishable and aroma-sensitive foods. They are also important for cosmetics and pharmaceuticals, helping to ensure product effectiveness and shelf life.

In technical sectors, BO-PET barrier films are used in electronics for flexible printed circuits, insulation materials, and displays; in electrical engineering for insulation layers in relays and transformers; and in the solar industry as back sheets for photovoltaic modules.

In the printing industry, BO-PET barrier films are used for laminations and various printing applications.

Typical applications

• Coffee and tea packaging
• Packaging for snacks and dry products
• Frozen food packaging
• Microwave packaging
• Pharmaceutical blister packs
• Sterile packaging
• Printed circuit boards and displays
• Protective films for electronic products

Recyclability of BO-PET barrier films

PET and BO-PET are generally recyclable plastics. The recycling loop for PET bottles is particularly well established, with a large proportion collected and returned to production cycles in Germany. BO-PET barrier films can also enter recycling streams if collected in a single-material format. However, recycling becomes more challenging when additional barrier coatings are applied. Although research is ongoing, for example with ultra-thin barrier layers, such composite materials are still difficult to recycle efficiently.

Approaches to improving sustainability

There are experimental enzymatic degradation processes in which bacteria break down plastic waste into its basic components for reuse in production. However, these methods are not yet widely implemented on an industrial scale. More progress has been made in developing polyester raw materials derived from renewable resources instead of petroleum-based feedstocks. Although their market share remains limited, such alternatives are already available. As sustainability is an important issue for many users of BO-PET barrier films, intensive research is ongoing in this area.

Alternatives to BO-PET barrier films

Films made from amorphous polyethylene terephthalate (A-PET) also offer strong barrier properties but lack the mechanical strength of BO-PET barrier films. Other alternatives include polyethylene (PE), polypropylene (PP), ethylene-vinyl alcohol copolymer (EVOH), and polyamide (PA). However, all non-PET alternatives are likewise derived from petrochemicals. Currently, there is no film made from renewable raw materials with comparable barrier properties available on the market. As alternatives often rely on less established recycling processes, BO-PET barrier films are presently considered one of the more environmentally responsible barrier film options.

Details on the barrier performance of BO-PET films

BO-PET barrier films protect packaged goods from gases such as oxygen and carbon dioxide. By limiting oxygen exposure, they help prevent product spoilage and preserve freshness.

They also prevent aroma loss and the absorption of foreign odors. In this way, they act not only as gas barriers but also as aroma barriers, helping maintain a product’s distinctive flavor and scent.

Transparent and coated BO-PET barrier films

In their original state, BO-PET barrier films are transparent. Even without additional coatings, they offer strong barrier properties while allowing full product visibility – often important for marketing purposes.

Barrier performance can be further modified through coatings. Metallic coatings significantly enhance barrier properties, which is why aroma-sensitive products such as coffee or snacks are often packaged in metallized BO-PET barrier films.

In addition, metal coatings reflect incoming light and UV radiation, contributing to improved product shelf life. Metallized BO-PET barrier films are therefore used not only for enhanced barrier performance and light protection but also for decorative purposes.

They provide product packaging with a visually appealing, high-quality metallic finish.

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