VMPET stands for vacuum-metallised polyethylene terephthalate: polyester (PET) film carrying a very thin layer of aluminium deposited in a vacuum chamber. It is the material most people mean when they say “mylar film” or “aluminised polyester”, and it is the base of most reflective films, decorative laminates and barrier packaging structures.
How it is made
A roll of PET film passes through a vacuum metalliser. Inside, aluminium wire is evaporated from heated boats; the vapour condenses on the cold film as it passes, leaving a metal layer a small fraction of a micron thick. The film is then rewound, often corona-treated on one side so inks and adhesives bond, and slit to width.
Because the metal is deposited rather than rolled, the layer is far thinner than any aluminium foil. That is what makes VMPET light, flexible and inexpensive, and also what limits it: the layer can be abraded, and it does not stop water vapour or oxygen as completely as solid foil.
What it is used for
- Reflective surfaces: grow-room and greenhouse lining, reflective insulation facings, lamp and reflector components.
- Barrier packaging: the silver layer in snack, coffee and pharmaceutical pouches, laminated between PET and PE.
- Decoration: gift wrap, labels, balloons, textile trims, holographic and coloured films.
- Laminate faces: the reflective face of woven grow-tent fabrics, foil-bubble and foil-foam insulation, and cooler-bag liners.
Grades you will see quoted
The names below turn up on quotes and data sheets, and they describe different things: some the finish, some a surface treatment, some which face carries the metal.
| Grade | What it means | Typical use |
|---|---|---|
| Single-sided | Aluminium on one face | Packaging, laminate faces |
| Double-sided | Aluminium on both faces | Reflective liners, insulation |
| Mirror / bright | High optical density, specular finish | Reflectors, grow rooms |
| Matte | Diffuse finish | Soft light, low glare |
| Corona-treated | Surface energy raised for print and adhesive | Printing, laminating |
| Coloured / holographic | Lacquer or micro-emboss over the metal | Decoration, security |
Thickness is quoted in microns for the PET base; the aluminium layer is described by optical density rather than thickness.
What optical density tells you
Optical density is a logarithmic measure of how much light the metal layer blocks: an OD of 2 passes one per cent of the light, an OD of 3 passes a tenth of one per cent. Because the aluminium is only a fraction of a micron thick, OD is a more practical way to specify it than a thickness figure nobody can measure with a gauge. A higher OD means more metal, which generally means a more opaque and more reflective film, but also a layer that is slightly more prone to cracking at a sharp fold. When two suppliers quote “silver VMPET” at different prices, the optical density is often where the difference sits. Ask for it, and ask which side it was measured from on a single-sided film.
VMPET, plain PET and aluminium foil
Plain PET is the same film without the metal: clear, strong and printable, but not reflective and a poor barrier. Aluminium foil laminate uses solid foil, several microns thick, bonded to a carrier: heavier, less flexible, better barrier, lower emissivity. VMPET sits between them. Choose it when you need reflectivity, appearance and low weight; choose foil when you need the best barrier or heat performance.
How to specify VMPET
State the PET thickness in microns, single or double sided, mirror or matte, corona treatment and which side, roll width and length, core diameter, and what the film will be laminated or printed onto. If a fire rating is needed, name the standard. A swatch of what you use today lets us match it directly.
We supply VMPET by the roll, slit to width, plain or laminated to scrim, foam, bubble and PE — for example Grid Reflective Film, Silver and Satin Reflective Film, Smoke Grey. Ask for swatches and a data sheet.