How PET Plastic Sheets Are Manufactured

Three-Roller Calendering and CoolingWith the rise of environmental awareness, PET (Polyethylene Terephthalate) plastic sheets have become widely used in food packaging, electronic product protection, printing, and advertising, thanks to their high transparency, strength, and recyclability. But how exactly are these sheets produced? Let’s take a detailed look at the manufacturing process.

Raw Material Preparation and Drying

The main raw material for PET sheet production is PET resin pellets, sometimes blended with recycled PET (RPET) pellets. Since PET is highly sensitive to moisture, excessive water content can lead to hydrolysis during extrusion, reducing transparency and mechanical strength.

To prevent this, the pellets are first dried in specialized hot-air or dehumidifying dryers at around 160℃–180℃, lowering the moisture content to less than 0.005%.

Melting and Extrusion

After drying, the PET pellets are fed into an extruder through a vacuum loader. Inside the extruder, the material is heated step by step to 260℃–280℃ and melted by the combined action of heat and screw shear force.

The molten PET is filtered through fine screens to remove impurities and black spots, ensuring high clarity and cleanliness of the final sheet.

Sheet Formation Through T-Die Casting

The molten PET is pushed through a T-die head, forming a wide molten film. The width of the die determines the sheet width, while the die gap controls the thickness.

At this stage, the material is still hot and viscous, requiring immediate cooling and shaping.

Three-Roller Calendering and Cooling

One of the most critical steps, clearly visible in the production line, is the three-roll calendering system. The hot PET melt passes through three rollers—cooling roll, shaping roll, and traction roll—where it is gradually cooled, flattened, and solidified.

This step ensures:

• Flatness and uniform thickness of the sheet.

• High transparency and gloss without bubbles or waviness.

• Optional surface effects, such as embossed or patterned sheets, depending on the roller design.

Haul-off and Winding

The cooled and shaped PET sheet is pulled out by a haul-off unit and then processed in two main ways:

1. Winding into rolls – suitable for continuous production and easy transportation.

2. Cutting into sheets – convenient for printing, folding, and thermoforming applications.

Additional treatments, such as anti-fog coating, scratch resistance, or lamination, can also be applied at this stage depending on customer requirements.

Quality Inspection and Applications

Before leaving the factory, PET sheets undergo strict quality testing, including:

• Transparency and gloss

• Thickness uniformity

• Tensile and impact strength

• Food safety compliance (FDA, EU standards)

Qualified PET sheets are then used in a wide range of industries, including food packaging (fruit boxes, cake containers), folding cartons, blister packaging, printing, and protective films.

Conclusion

The manufacturing of PET plastic sheets generally follows the process of raw material drying → extrusion → T-die casting → three-roll calendering → haul-off & winding → quality inspection. Each step requires precise control of temperature, humidity, and pressure to ensure excellent sheet performance.

With growing demand for sustainable and recyclable packaging, PET sheets will continue to play an important role in modern packaging and industrial applications.