Most people have never heard of polyester film, yet most of us handle it several times a day. It is made from polyethylene terephthalate (PET), the same polymer as most drinks bottles, stretched in two directions into a thin, strong, clear film. Once you know what to look for, you start to see it everywhere: on your lunch, in your wallet, inside your phone, on your roof and in the archives that keep our history safe.
It is easy to miss for two reasons. It is thin: most packaging and label films are thinner than a human hair. And it usually works out of sight, sealing something in, keeping something out, or stopping electricity going where it should not. Here is a tour of where it turns up, and why.
In the kitchen and the supermarket
Peel the lid off a ready meal and there is a good chance it is polyester. PET lidding film is heat sealed to the tray, holds the food in through chilling and transport, and in suitable grades can go into the oven with the tray. Peelable grades are designed to come away cleanly in one piece.
The clear window in a cake box, a sandwich pack or a carton of biscuits is often polyester too. It is crystal clear, stiff enough to stay flat across the opening and strong in thin gauges, so the product is on show without adding weight, and our guide to choosing carton window film compares it with the alternatives. Inside many coffee and snack packs, a metallised polyester layer adds a barrier to light, oxygen and moisture. Our page on PET packaging film covers lidding, windows and sealing films in detail.
In your wallet and on the shelf
Durable labels, the barcodes on parcels and the asset tags on equipment are often printed on white or clear polyester, because it resists tearing, water, abrasion and heat far better than paper. Many of those barcodes are printed with thermal transfer ribbons, which are themselves coated polyester film a few microns thick. Polyester films are also used in ID cards, security passes and secure documents.
Shop displays, backlit signs and the printed overlays on control panels use polyester for the same reasons: it holds its size through printing and stays flat and clear for years. Our guide to polyester film for labels, graphics and print explains how it is chosen.
In your phone, your home and on your roof
Many screen protectors are made of polyester film, and inside screens and touch panels, thin polyester films are used for optical layers and touch sensors. On the front of a microwave or washing machine, the flat keypad is usually a membrane switch: printed polyester layers with conductive tracks between them.
Behind the scenes, polyester is one of the most widely used electrical insulation materials. It lines the slots of the electric motors in fridges, washing machines and cars, wraps the coils of transformers, and insulates cables and battery cells. On the roof, the backsheet that protects many solar panels from moisture and electrical faults is a laminate built around a polyester layer. See polyester film for electrical insulation for the grades and data.
On the road
A car contains polyester film in places its driver never sees. Insulation laminates with a polyester layer line the slots of electric motors, including the traction motors of electric vehicles, and polyester films insulate and separate cells inside battery packs. Colour-coded polyester shims and spacers set precise gaps in assemblies such as brakes and clutches, where they must resist oils and hold their thickness without corroding.
In the archive
For decades, polyester was the base film for audio and video cassettes and computer data tape: the magnetic coating that held the music, the film or the data sat on a ribbon of polyester only a few microns thick. Polyester is also the base for X-ray film and microfilm, chosen because it stays the same size and does not degrade.
The same stability, with no plasticisers or coatings to migrate, is why museums, libraries and archives use polyester sleeves and encapsulation to protect documents and photographs. Our guide to protecting old documents and photographs explains how encapsulation works.
In hospitals, workshops and emergencies
When the world needed face shields in 2020, clear polyester was one of the materials it turned to: tough, light and optically clear, with anti-fog grades for comfort. Polyester is also a base for diagnostic test strips and is cut into parts for medical equipment. In workshops, colour-coded polyester shims set precise gaps in machinery, and the silver emergency blankets handed out at marathons and mountain rescues are metallised polyester. Our guide to polyester film for industrial and medical uses covers more.
Why polyester is chosen
The same handful of properties explain almost all of these uses:
| Property | What it means | Everyday example |
|---|---|---|
| Strength in thin gauges | High tensile and tear strength for its thickness | Lids, windows and labels that do not tear |
| Clarity | Glass-clear in suitable grades | Carton windows, face shields, screen protectors |
| Heat resistance | Polymex® polyester: service from minus 70°C to 130°C, melting point 265°C | Ovenable lids, motor insulation |
| Dimensional stability | Holds its size through heat, print and time | Printed overlays, magnetic tape, microfilm |
| Electrical insulation | High dielectric strength and resistivity | Motors, transformers, solar panel backsheets |
| Chemically inert | Archival grades contain no plasticisers or coatings | Document and photograph sleeves |
| Recyclable | PET is one of the most widely recycled plastics | Packaging films with recycled content |
Where PSG fits in
PSG has worked with polyester film since 1969, when it introduced colour-coded polyester film to the market, and in 1983 it became the largest polyester film converting plant in the UK at the time. Today we supply polyester film under our own Polymex® brand and from the world's leading manufacturers, and convert it into the reels, sheets and parts that end up in many of the products above: carton window and packaging films, archival films, insulation, colour-coded shims and components cut to drawing. For an overview of everything we do with PET, see our guide to polyester (PET) film supply and converting.
Have a product that could use polyester film? Talk to our technical team about the application, and we will recommend the right film and supply it ready for your line.
