GAG PET film

Definition of GAG PET film

GAG PET film is a plastic composite material based on polyethylene terephthalate (PET), with a sandwich-like structure consisting of three layers. This special multilayer structure combines the properties of the different PET types used for the film and thus ensures good transparency and strength as well as optimized processability of the material. The term “GAG” describes the layered structure of the film. A central layer of amorphous PET (A-PET) is enclosed on both sides by layers of glycol-modified PET (PET-G). In order to understand the structure, properties and function of GAG PET film, it is necessary to take a closer look at the properties of A-PET and PET-G.

What is amorphous PET?

A-PET is produced by rapidly cooling liquid polyethylene terephthalate to a temperature below around 80° Celsius, the so-called glass transition temperature. This rapid drop in temperature prevents the formation of crystalline structures, which keeps the material transparent. By contrast, slow cooling leads to crystallization, which makes the material appear opaque. However, the crystallinity of other PET materials is partly responsible for the good heat resistance and mechanical strength that A-PET lacks. In return, A-PET is a popular material due to its clear appearance and good formability, for example for beverage bottles and transparent packaging. It is also frequently used for carton packaging with curved transparent windows. It offers good barrier properties against gases and moisture, but is sensitive to heat. At around 80° Celsius, the material begins to deform as it then changes into a partially crystalline state.

What characterizes PET-G?

In the production of PET-G, glycol is added to the PET during polymerization. This additive prevents crystallization even at higher temperatures, so the film remains permanently clear and transparent. PET-G also offers excellent thermoforming properties, making it well suited for complex moulded parts. Its break resistance is also higher than that of A-PET. Thanks to its improved behaviour at low processing temperatures, PET-G is suitable for applications where detail accuracy and precise edges are required. One weakness is its lack of UV resistance. For this reason, PET-G is not suitable for permanent outdoor use.

Combination in GAG PET film

The combination of PET-G and A-PET into a three-layer GAG PET film brings together the strengths of both materials in one product. The middle A-PET layer provides mechanical strength, stability and a cost-efficient basis. In addition, recycled material can be used in the production of this core layer, which improves the environmental balance. The outer PET-G layers give the film the clarity desired for transparent packaging and make it well suited for thermoforming. Due to the PET-G outer material, GAG PET films are printable and sealable. Solvent-based adhesives can also be used on the surfaces without any problems. However, GAG PET film also remains unsuitable for outdoor applications, as the PET-G layers are not resistant to UV radiation.

Advantages of GAG PET films

• Good transparency and glossy surface
• High break resistance and impact strength thanks to the PET-G layers
• Good thermoforming properties at moderate temperatures
• Good barrier effect against aromas, moisture and oxygen thanks to the A-PET core
• All three layers consist of PET, making GAG PET film recyclable within the PET cycle
• Resistant to fats, oils and various cleaning agents
• Very easy to print and seal with suitable surface treatment

The manufacturing process of GAG PET film

GAG PET film is produced using a coextrusion process. The three layers – two made from PET-G and one made from A-PET – are melted in separate extruders. The melts are brought together in a slot die. It is important to ensure an even and controlled layer distribution. To avoid hydrolysis, the PET granulates used must be carefully dried beforehand. After leaving the die, the film is rapidly cooled on a chill roll so that its amorphous structure is preserved. The film is then cut and wound, and the surface can be finished if required. Depending on the final application, the thickness of the individual layers can be adjusted.

Typical applications of GAG PET film

• Packaging solutions

GAG PET films are suitable for blister packaging, for example for toys, electronic items or tools. In food packaging, trays and lids with a clear view of the product and good barrier properties are also made from this material. Cosmetic packaging made from GAG PET film benefits from the combination of stability and aesthetic presentation.

• Medical supplies

In medical technology, GAG PET film is used for packaging sterile disposable instruments or consumables. The dimensional stability and high hygienic quality of the material are the decisive arguments in this sensitive area.

• Technical applications

GAG PET film is also used as a transparent, scratch-resistant protective layer, for example for displays or control panels. In thermoforming, it is used to produce housing parts, trays for multiple product packages or components for vehicle interiors.

• Graphic products and advertising

Thanks to its good printability and high transparency, GAG PET film is popular for displays, signs, transparent packaging and similar advertising applications. It is also used for office supplies or stickers for indoor use.

Sustainability and environmental friendliness of GAG PET film

GAG PET films can be effectively recycled in existing PET recycling systems because they consist entirely of one material type. By contrast, many other multilayer films can only be thermally recovered because they consist of different film materials that cannot be separated for the recycling process. GAG PET films contain neither chlorine nor plasticizers and are therefore considered easier to dispose of and less harmful to the environment during the production process. The relatively low processing temperature reduces energy demand during further processing. In addition, the middle A-PET portion can consist fully or partly of recyclate, which supports resource conservation. Nevertheless, GAG PET film is a petroleum-based product whose environmental balance depends heavily on standardized and complete return into the recycling cycle. Efforts are being made to produce the raw materials for PET from renewable resources. However, these raw materials do not yet have a significant market share. A positive aspect is that GAG PET film can replace PVC in many cases, a plastic with a significantly poorer environmental balance.

GAG PET film is produced by coextrusion

Both components of GAG PET film are made from polyethylene terephthalate and are jointly extruded into a sandwich film by coextrusion. Pure A-PET retains very good transparency thanks to its amorphous structure. However, the material offers only limited possibilities in terms of mechanical load capacity, impact strength and thermoformability. PET-G remains amorphous even at higher temperatures due to glycol modification and offers very good toughness as well as excellent forming properties. The three-layer GAG structure uses these material differences to produce films that combine the advantages of both materials. Due to the PET-G content, the material is very easy to thermoform.

Thermoforming with GAG PET film

GAG PET film shows its advantages particularly well in the thermoforming process. During thermoforming, the film is heated and then drawn or pressed into a mould. The outer PET-G layers of the GAG PET film improve the forming behaviour of the material and reduce the risk of stress whitening or stress cracks. The A-PET in the core of the GAG PET film provides dimensional stability, helps reduce material costs and increases the usable recyclate content, which improves the sustainability of the films. Through the targeted use of different layer thicknesses, the property profile of GAG PET film can be precisely adapted to the respective application. For particularly complex geometries, for example, a higher PET-G content is used.

Surface modifications of GAG PET film

GAG PET films are available on the market with different surface modifications. For printing applications or laminations, GAG PET films are often finished by corona treatment or plasma treatment. Both pretreatments increase the surface energy, enabling better adhesion of inks, varnishes or adhesives. Anti-fog coatings or antistatic coatings can also be applied. This makes the material suitable for many packaging solutions, from classic blister packaging to high-quality presentation packaging in the premium segment.

GAG PET film is a versatile material with easily adjustable parameters

GAG PET film is the material in the PET family for demanding thermoforming applications. As a further development of monofilms made from A-PET or PET-G, it specifically combines mechanical stability, optical quality and good processing properties. It is mainly used where high transparency and dimensional stability are required and where cost-effectiveness and sustainability also play an important role. GAG PET film is a technically optimized PET composite that combines transparency, mechanical performance and good processability. With the high possible recyclate content of the A-PET layer, the film scores well in terms of both cost-effectiveness and sustainability.

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