What Is PET Film Made Of?

pet film, also known as polyethylene terephthalate film, is one of the most versatile plastic films used across packaging, electronics, printing, and industrial applications. It combines strength, transparency, and chemical resistance, making it an essential material in modern manufacturing. To understand its performance and value, it is important to explore what pet film is made of, how it is produced, and what properties make it superior to many other polymers.

1. The Chemical Composition of PET Film

PET film is made primarily from polyethylene terephthalate, a thermoplastic polymer produced through the reaction of terephthalic acid (TPA) and ethylene glycol (EG). This process is called polycondensation, where water molecules are removed as the two components bond together to form long-chain polyester molecules. The resulting polymer has strong intermolecular forces, giving the film its notable tensile strength and dimensional stability.

Key Ingredients and Their Roles

During polymerization, the monomers link together to form a repeating unit –(O–CH₂–CH₂–O–CO–C₆H₄–CO)–. This structure is responsible for the film’s toughness and resistance to deformation under heat and tension.

2. The Manufacturing Process of PET Film

The transformation of raw polymer into a usable PET film involves several critical steps. These steps define its physical appearance, surface texture, and mechanical strength.

2.1 Extrusion and Casting

In the first stage, PET resin pellets are melted and extruded through a flat die onto a chill roll. This forms a thick amorphous sheet that is quickly cooled to solidify the polymer chains in an un-oriented state. The cooling process determines the film’s initial clarity and surface smoothness.

2.2 Biaxial Orientation

Once the sheet is formed, it undergoes biaxial stretching, meaning it is stretched in both the machine direction (MD) and transverse direction (TD). This orientation aligns the polymer molecules, significantly improving the film’s tensile strength, thermal stability, and barrier properties. The ratio of stretching often ranges from 3:1 to 4:1 in each direction.

2.3 Heat Setting

After orientation, the film is heated under controlled tension in a process called heat setting. This locks the molecular orientation in place, reducing shrinkage and giving the film high dimensional stability. Heat setting temperatures usually range from 200°C to 230°C.

2.4 Surface Treatment and Coating

To enhance adhesion and printability, PET film surfaces are treated using corona discharge or chemical coating. This improves surface energy, allowing inks, adhesives, or metallization to bond effectively. Specialized coatings may also be applied for anti-fog, anti-scratch, or anti-static purposes.

3. Material Characteristics and Properties

The combination of its molecular structure and processing techniques gives PET film a balanced set of mechanical, optical, and chemical properties. Each property contributes to its suitability for various industrial and consumer applications.

3.1 Physical and Mechanical Properties

These characteristics make PET film ideal for high-speed lamination, die-cutting, and precision packaging where durability is essential.

3.2 Thermal and Chemical Stability

PET film withstands high temperatures up to 150°C (302°F) without distortion. It also maintains its form under cold conditions as low as –70°C (–94°F). Chemically, PET film is resistant to oils, alcohols, and mild acids, though it can be attacked by strong alkalis.

3.3 Optical and Barrier Properties

PET film is naturally transparent with excellent gloss and clarity. It allows light transmission of around 88–90%, making it a preferred choice for display panels and optical coatings. Its oxygen and moisture barrier capabilities protect packaged goods from oxidation and contamination.

4. Common Variants and Formulations

To meet the requirements of different industries, manufacturers produce several PET film variants with specific enhancements.

4.1 metallized pet film

A thin layer of aluminum is vacuum-deposited on one side of the PET film. This gives the film a metallic appearance and enhances its light, gas, and moisture barrier properties, making it ideal for food packaging, insulation, and decorative labels.

4.2 coated pet film

PET films may be coated with acrylic, silicone, or PVDC (polyvinylidene chloride) to improve surface adhesion or weather resistance. Coated films are widely used in the graphics industry and photovoltaic back sheets.

4.3 White or Opaque PET Film

This version includes titanium dioxide or other pigments to create a reflective, non-transparent film. It’s used in applications requiring light blocking, such as insulation labels or backlit panels.

4.4 Heat Sealable PET Film

Modified with special copolyesters, this film can be sealed to itself under moderate heat, simplifying packaging operations. It maintains PET’s durability while adding convenience for flexible packaging.

5. Advantages Over Other Plastic Films

PET film competes with materials like polypropylene (PP), polyvinyl chloride (PVC), and polyethylene (PE). However, it stands out for its superior balance of strength, clarity, and recyclability.

Because of these advantages, PET is increasingly replacing PVC and other plastics in industries that require sustainability and performance consistency.

6. Environmental and Recycling Aspects

PET film is part of the polyester recycling ecosystem, making it one of the most sustainable engineering plastics. After use, it can be collected, washed, and reprocessed into rPET film or fibers for textiles, strapping, and new packaging materials.

6.1 Recycling Process

1. Collection and Sorting – Used PET products are separated based on color and purity.

2. Washing and Shredding – Contaminants are removed and the material is cut into flakes.

3. Repolymerization – The flakes are melted and re-polymerized to restore molecular weight.

4. Film Extrusion – Recycled PET is extruded into new films with slightly lower mechanical strength but still suitable for non-critical applications.

6.2 Sustainability Benefits

Recycling PET film reduces landfill waste, lowers CO₂ emissions, and conserves petroleum resources. It also enables circular manufacturing practices where post-consumer materials are reintegrated into the production line.

7. Industrial Applications of PET Film

Because of its durability and clarity, PET film is widely used in multiple industries. The combination of flexibility, printability, and strength makes it adaptable to both high-tech and consumer products.

• Packaging – For food, pharmaceuticals, and consumer goods due to barrier and sealing properties.

• Electrical Insulation – Used as dielectric material in capacitors and flexible circuits.

• Printing and Labels – Ensures vibrant color reproduction and tear resistance.

• Solar and Automotive Films – Provides UV resistance and dimensional stability.

• Lamination and Coating Base – Used as a substrate for adhesives and protective layers.

Each application leverages a specific set of PET film’s attributes—from heat stability to optical clarity—to achieve reliable performance.

Summary

PET film is made from polyethylene terephthalate, a polymer derived from terephthalic acid and ethylene glycol through a condensation reaction. The film’s properties—strength, transparency, heat resistance, and recyclability—are the result of controlled biaxial orientation, heat setting, and surface treatment during manufacturing. Various modified versions, including metallized, coated, and heat-sealable types, expand its use across packaging, electronics, automotive, and printing sectors.

Its combination of performance, versatility, and sustainability ensures that PET film remains one of the most important materials in global industrial production, balancing technological efficiency with environmental responsibility.