printing on plastics

The need to print on plastics is becoming increasingly necessary for many businesses. Beyond paper, innovative technology employed by inkjet printers today allows businesses to print directly on plastic products.

Therefore, it’s essential for business owners to be aware of the kind of plastics that are commonly available in the market and the types of printers that are uniquely optimized to print on them.

To get you started, here are a few things you should know about printing on plastics:

Printing Surfaces

Currently, there are several options in terms of plastic surfaces for businesses to choose from for their packaging. Each of these sheets has advantages and disadvantages of their own. Depending on the requirement for your business and the printing budget for your operations, there are 4 major types of sheets available:

  • Polystyrene – Commonly used for both signage and packaging services, this material is ideally suited for cost-effective processes. Being recyclable and device friendly, printing high-resolution designs on these sheets is easier. However, they are not that malleable and can’t be folded. They are not compliant to come in direct contact with edible goods and tend to become brittle with time.
  • Polypropylene – This material is commonly used to manufacture polyethylene bags, labels and tags. Easy to fold, this material is light and easily recyclable. It is also compliant for direct contact with food. Ideal for printing simpler designs, these sheets are difficult to bond. They are not as tear resistant as other options either.
  • Rigid Vinyl – Polyvinyl Chloride also known as rigid vinyl is one of the most popular printing materials. Really durable, PVC is device friendly and resistant to UV degradation. However, it lacks the flexibility of Polypropylene and is not as recyclable either.
  • Polyester – Polyethylene terephthalate or PET is commonly used for making outdoor-friendly resources such as masts for sailboats and nameplates. Tough and stable, this material is machine friendly. It is also expensive as compared to other options and not as flexible either.

Surface Tension of the Substrate

The same way an insect like the water strider can stand on water’s surface without falling in, surface tension plays a role in whether the ink will properly adhere to the plastic or just wipe away when touched.

To ensure ink adhesion to the plastic surface, it’s recommended that the surface tension of the ink should be at least 10 dynes lower than the surface free energy of the plastic sheet. This is because liquids don’t dampen planes with surface free energy lower than the surface tension of the liquid. Translation: if you’ve got a bad surface tension/surface free energy match up, the ink will sit atop the plastic, barely contacting the plastic itself. If you have a good ink/surface match, the ink will lay flatter against the plastic, allowing it to “wet” or “dampen” the plastic surface (and that’s what you want). According to Printing.org, for ideal inkjet printing you should select plastic sheets with free surface energies between 40-50 dynes. Always keep in mind, however, that this number varies for different printers and printing techniques.

Printing Methods

For basic barcode printing onto plastics, an industrial-quality Continuous Inkjet (CIJ) is recommended due to its effectiveness and variety of options. Brands like Anser offer CIJs at a low cost with fewer capabilities for a ‘starter’ version. Brands such as Leibinger and Matthews produce inkjets with more options and better reliability at a medium-to-high cost. These inkjet printers can be mounted along your production line so your product packaging does not need to leave the facility to be printed.

Thermal transfer printing can also be employed when printing onto plastics. However, a special coating must be applied or specialized plastic must be used for the thermal print to work.

Traditional print methods like screen, flexo, and gravure print methods will also print directly onto plastics, however these require more space, equipment, operators and a much longer setup time – therefore, these methods are often left to a commercial print shop to employ. They’re generally associated with a detailed, full-colour print like a product label or a flat surface like a printed storefront sign.

From printing codes onto labels, to directly marking your tape or packaging, there are many types of printers and techniques to choose from. If you have more questions about inkjet technology and printing onto plastics within your manufacturing facility, feel free to get in touch with our knowledgeable team at Jet Marking Systems.

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