APET vs. CPET: Understanding the Differences in Food Packaging

When it comes to food packaging, selecting the right material is crucial for ensuring product quality and safety. Polyethylene terephthalate (PET) is a widely used plastic material in the packaging industry, particularly for food and beverage containers, cups, and trays. It’s available in two forms: APET (Amorphous Polyethylene Terephthalate) and CPET (Crystalline Polyethylene Terephthalate), each with its unique properties and applications.

Diving into the molecular world

APET is the amorphous, or non-crystalline, form of PET. It is transparent, rigid, and has good barrier properties against moisture and gases. APET is also known for its clarity and glossy appearance, making it an attractive choice for packaging applications where product visibility is essential.

CPET, on the other hand, is the crystallized form of PET with a well-defined molecular arrangement. This results in a material with higher thermal stability, improved chemical resistance, and better barrier properties compared to APET.

The production of APET and CPET trays involves similar processes, including extrusion and thermoforming. However, CPET requires additional elevated temperatures (typically between 120°C and 240°C) for a specific duration, allowing the polymer chains to reorganize and form a crystalline structure. The degree of crystallinity can be controlled by adjusting the temperature and duration of this heat treatment process. As a result, CPET trays tend to have higher heat resistance and mechanical strength compared to APET trays. APET is produced through a standard extrusion or thermoforming process, where PET resin is melted and formed into the desired shape. The rapid cooling rate during this process results in an amorphous structure.

Variety of Food Applications

APET trays are commonly used for applications where clarity and product visibility are prioritized, such as fresh produce packaging, bakery items, and certain ready-to-eat meals. They offer excellent transparency, allowing consumers to clearly see the contents of the package. APET's rigidity, moderate barrier, and heat resistance properties make it suitable for short-term storage and display purposes.

CPET trays, on the other hand, are preferred for applications that require higher thermal stability, chemical resistance, and better barrier properties. These trays are often used for packaging hot-filled products, such as retorted or pasteurized foods, as they can withstand the high temperatures involved in these processes without deforming or losing their structural integrity. Additional applications are microwave and oven-ready meals or frozen foods. Their crystalline structure provides superior heat resistance, allowing them to withstand temperatures ranging from -40°C to +220°C without deformation. CPET trays are also suitable for extended shelf-life applications due to their superior barrier properties.

Sealing with Top Films

When sealing APET or CPET trays with a top film, it is essential to consider the compatibility of the materials and the sealing conditions. For both trays, heat-sealable top films can be used that have a PET-containing sealing layer (like PETg for example).

Another option is to coat the APET tray with PE layer that can easily seal to PE top lid. There are special machines that offer a very thin coating layer that is easily washed and removed during recycling, facilitating a full recycling process of the PET tray.

In summary, APET and CPET offer distinct advantages based on their properties and production conditions. APET trays are well-suited for applications where clarity and moderate barrier properties are required, while CPET trays excel in applications demanding high thermal stability, chemical resistance, and superior barrier properties. Understanding the differences between these materials is essential for selecting the right packaging solution to meet specific product requirements and ensure optimal performance throughout the supply chain. Whether you're packaging cold salads or hot entrees, choosing the appropriate material can make a significant difference in product quality and consumer satisfaction.