An Analysis of the Thermoforming Process, Machine Structure, and the Use of Recycled PET for Sustainable and High-Quality Food Packaging

by Marco Arezio

Thermoforming is a fundamental technique for producing food trays, and the use of PET (polyethylene terephthalate) represents an ecological and versatile choice. This article explores the functioning of thermoforming, describing the various stages of the process, the structure of the machines involved, and the important role of recycled PET.

The Structure of the Thermoforming Machine

Thermoforming machines are complex and sophisticated, designed to transform plastic sheets into finished products through heat and pressure. A typical thermoforming machine consists of several essential components.

The heart of the machine is the heating system. This can include infrared, electric, or contact heaters, which bring PET sheets to high temperatures, usually between 140°C and 160°C, making them malleable. It is crucial that the heating is uniform to ensure homogeneous and high-quality forming.

Once heated, the sheets move to the forming station. Here, the PET is molded using a die. Forming can occur through vacuum, where a vacuum pulls the sheet onto the mold, or through pressure, which pushes the sheet into the desired shape. In some cases, a combination of both methods is used to achieve optimal results.

After forming, the trays need to be separated from the residual sheet. This occurs at the cutting station, where blades or laser systems make precise cuts to obtain the final product. The excess material can be recycled and reintroduced into the production cycle, minimizing waste.

Finally, the formed trays pass through a cooling system to solidify their shape. This cooling can be air or water-based, depending on the specific needs of the material and product.

All these operations are managed by a central control unit, which monitors and regulates parameters such as temperature, pressure, and process speed. This ensures that each tray is produced with precision and consistency, maintaining high-quality standards.

The Use of Recycled PET

A significant aspect of using PET in thermoforming is the possibility of employing recycled material.

Recycled PET comes primarily from used bottles and other containers, which are collected, cleaned, and ground into small fragments. These fragments are then decontaminated and transformed into granules through an extrusion process. The obtained granules can be reformed into new PET sheets, ready to be used in thermoforming.

The use of recycled PET offers numerous advantages. First, it reduces dependence on fossil resources and helps lower CO2 emissions. Additionally, using recycled materials helps reduce plastic waste, promoting environmental sustainability.

Thanks to technological advancements, it is possible to produce recycled PET sheets with characteristics very similar to those of virgin material. This means that trays made from recycled PET can offer the same quality and safety as those made from virgin PET, making them suitable for food use.

Moreover, it is possible to produce triple-layer PET trays, where non-food grade or non-virgin PET flakes are used in the central layer, while the outer layers can be composed of food-approved PET. This type of application helps reduce the production costs of PET trays.

Conclusions

Thermoforming PET sheets represents an advanced and versatile technique for producing food trays. The sophisticated structure of thermoforming machines and the well-defined process allow for high-quality products, essential for food packaging.

The use of recycled PET, in particular, offers significant environmental benefits, contributing to sustainability and reducing the ecological impact of the plastics industry. This approach not only reduces waste but also promotes a circular economy, where materials are continually reused.

In an era where sustainability has become a global priority, adopting techniques such as PET thermoforming and using recycled materials represent important steps toward a greener and more responsible future.