The materials that you use for your cards make a big difference. Choosing which plastic cards to buy for your printer can be overwhelming. There are literally hundreds of types of cards on the market.
In this post I would like to show you what materials cards are made out of and how to choose the correct one. Later maybe I could cover also the encoding options (Magstripe, Chip, and Contactless cards) as well as security features.
Basics of ID Card Printing
During the card printing process, heat is used to transfer ink from a film into the surface or substrate of a plastic card. There are four basic processes used in all desktop card printing: Thermal transfer, Dye sublimation, Reverse transfer and Thermal rewrite.
Each process uses different methods of transferring the ink onto the substrate and thus each has different requirements for the thermoformability of the substrate. Additional processes such as card lamination can also deliver a lot of heat to a card and thus require cards that have more thermo stability to keep the card from melting and jamming the printer.
Plastic Card Materials
So, what type of cards should you choose? In general, there are two types of plastics used in modern card production: PVC and PET.
PVC – popular, durable but not eco-friendly
The most commonly used material in ID card printing is Polyvinyl Chloride or PVC. This ubiquitous white plastic is famous for making pipes, bottles, construction materials, medical equipment, inflatable toys and wire insulation. PVC cards are extremely inexpensive and relatively durable.
Pure PVC is rigid and brittle so more commercially available cards are plasticized using derivatives of phthalic acid. Additionally, heat and UV stabilizers are often added to improve durability and heat resistance. These additives allow PVC to withstand temperatures of up to 260°C, though in general, the thermal stability of PVC is very poor with pure PVC becoming thermally unstable at about 140°C.
For this reason, PVC is not a good choice for card processes that require a large amount of heat. Printing methods such as Reverse Transfer must be carefully monitored when using pure PVC cards to avoid damage to the card and the printing unit.
PET – durable and recyclable
Plain polyethylene terephthalate (PET) or polyester is most commonly associated with a material from which cloth and high-performance clothing are produced (e.g., DuPont Dacron™ polyester fiber). Increasingly over the last ten years, PET has gained acceptance as a material of choice for beverage bottles. Because of the improved performance and functionality of PET, it has managed to replace traditional bottle materials such as glass and aluminum, as well as, newer materials (e.g., PVC and polycarbonate). PET is more durable than PVC and is also recyclable, making it environmentally friendly.
PET-G – formable and environmentally friendly
PET-G, also known as glycolised polyester, is a modified PET material. The “G” represents glycol modifiers, which are incorporated to minimize brittleness and the premature aging that occurs if unmodified amorphous polyethylene terephthalate (APET) is used in the production of cards.
PETG films are amorphous, meaning the polymer molecules are not aligned or ordered within the material. It is produced in a roll calendering process similar to that used to make standard PVC. As a result, PET-G has many features similar to PVC with similar temperature resistance and durability.
In Europe, PET-G has found a market where customers are looking to produce “environmentally” friendly cards. In addition to its use in cards, this polymer is used in applications where thermoformability is required.
PET-F – the least used but promising
Polyester film (PET-F) is very different from PET-G and indeed PET. Polyester film is a semi-crystalline film produced by a roll quenching process followed by biaxial orientation (stretching the film in machine and transverse directions) and heat setting at temperatures around 230°C. Polyester film is used in many applications such as videotape, high quality packaging, professional photographic printing, X-ray film, floppy disks, etc. The film’s primary advantages are high thermal stability, mechanical strength and chemical inertness. In fact, PET-F has one-third the tensile strength of steel and can withstand temperatures of up to 200ºC. PET-F is produced in a range of thicknesses from 3 gauge (0.6 µm) to 2000 gauge (500 µm).
PET and its derivatives are much more thermally stable than PVC and produce cards that last for a long time. However, the strength and high thermo-stability of PET means that many direct to card printers cannot produce a good image on the substrate.
Composite cards containing up to 60% PET and 40% PVC material provide the stability of a PET card with the printability of a PVC card. These cards are constructed like a sandwich – two thin layers of PVC with a PET core between them. Composite cards are ideal for desktop card production and make a good “first step” when moving from PVC cards to PET.
- There are four basic processes in card printing: Thermal transfer, Dye sublimation, Reverse transfer and thermal rewrite.
- Most cards on the market are made of PVC.
- PVC is cheap and prints well, but it melts easily in high-energy processes (like Reverse Transfer and Lamination) and is not recyclable.
- There are several variants of PET available: PET, PET-G and PET-F
- PET-G is recommended for card production and is a vaild substitute for PET and depending on the process, PVC
- Composite cards combine a PET core with PVC substrates for durability and printability