How Adhesion Testing Promotes UV Printing’s Durability

Does UV printing scratch easily? A great question, and fully preventable! 

This story will resonate with everyone. Imagine having just returned from a weekend getaway by the ocean, where you enjoyed the sun, sand, and sea. As you unpack your weekender bag at home, you find traces of sand lingering at the bottom and even stuck behind your ear. Among your belongings, you discover the commemorative cup you bought during the trip. Filled with ice-cold water, you take a refreshing sip and place it on the counter. Later, while doing a load of laundry, you go back to the cup for another drink, only to notice that the design has already been scratched in transit! We’ve all experienced it, and we’ve all been disappointed with the short and nearly nonexistent life span.

But why does this happen? Why do some digitally decorated images scratch? Was the drinkware even digitally printed? (There are numerous methods of decorating!) Despite how often it has happened to all of us, it is completely avoidable with proper care and knowledge.

Three Critical Factors for Adhesion

When it comes to proper adhesion for UV printing, three factors are crucial:

• UV ink
• Proper pre-treatment
• Full transparency of the material being printed on

Neglecting any of these factors or making the wrong selection can result in scratching of a digitally decorated UV printed item.

UV Ink

There is no one-size-fits-all ink solution. For instance, the best ink to stick on acrylic will not be the same as one to stick on silicone. The bonding efficiency of ink to the substrate is influenced by various factors, including coatings, surface energy, dyne levels, and additional bonding criteria. That being said, adhesion can be boosted with proper pre-treatment. Pre-treatment comes in many different forms- from wipe on to jettable to flame, there are numerous options to find the best fit for your operations.

For the sake of today’s topic, let’s explore different UV inks for printing on different plastics that souvenir cups could be made from.

The LV Series UV printer ink is specially formulated for strongly adhering to rigid plastics printed with the Helix ONE®. Perfect for printing on acrylic cups, the LV series can stand alone or promote further adhesion by pairing it with an inkjet primer. The S1 UV inkjet series produces vibrant colors using CMYKW and Varnish on a variety of different plastic substrates. Part of the S1 line is a Vivid White shade that is highly opaque, perfect for decorating dark substrates.+

Alongside of the LV Series, we have six other UV digital ink series specially formulated for specific substrates; S1, XFLEXX, T2, Candymark, DL, and BB. For example, the T2 Series was designed for printing on Tritan Plastics. Highly sought after, Tritan plastics for drinkware are ideal due to its BPA free composition and its structure.

To learn more about the different series of UV digital ink we carry please visit our UV Ink page.

Pre-Treatment for Adhesion

The choice of substrate and its intended use determines the appropriate combination of primer and pre-treatment, or even the absence of it. For example, a pint glass that undergoes frequent washing would require a stronger adhesion compared to a candle holder that would never be exposed to a dishwasher. There are a handful of different pre-treatment methods to cater to different needs, Corona, Plasma, Flame, Pyrosil®, and proprietary systems like MagiCoat®  Pre-Treatment System.

To learn more about them, visit: UV Ink Adhesion Improvement Components.

Substrate

A crucial factor in printing is having a thorough understanding of the material you are printing on. When acquiring products, it is vital to carefully consider the material and rely only on trustworthy brands. It’s disappointing to discover that the products you ordered turn out to be different materials than expected. Moreover, this can lead to a waste of valuable time and resources, especially if you are utilizing specialized ink for a particular substrate, only to discover that the substrate does not match its apparent composition.

What is Adhesion Testing?

There are four ASTM standardized tests available for measuring adhesion in printing. The expectations for adhesion are typically determined by the printing company. In certain cases, long-lasting prints may not be necessary or required.

At Inkcups we ask customers to fill out a sample request form for this reason. It gives an overview of the specific pre-treatment needs, current printing process, and adhesion criteria. During the adhesion testing process, we are able to recommend the best pre-treatment method and ink series for the customers substrate.

The four methods of adhesion testing are tape adhesion, scratch adhesion, crosshatch A, and crosshatch B. As the name implies the tape adhesion test applies pressure-sensitive tape onto the printed surface with significant pressure from your thumb, then remove the tape at a 180-degree angle. If any ink comes up the test has failed. Next, the scratch adhesion test, uses a sclerometer (resembles a pen) and drags the sclerometer across the printed surface. This test has failed if any ink is lifted or if a line with jagged edges remains. Third up, crosshatch A is tested by using a razor blade to make an X-cut on a substrate and then complete the tape adhesion test over that area. Finally, a lattice pattern is cut into the printed surface for crosshatch B and must score a 5 to pass which indicates that all of the squares of the lattice remain intact.

We offer adhesion testing for our customers to ensure that they deliver exactly what their customers require.

For adhesion testing videos, please reference the following documents: Crosshatch A, Crosshatch B, Scratch and Tape Adhesion Testing.

Start digitally decorating today!

In conclusion, understanding the scratch resistance of UV printing is essential for achieving long-lasting and visually appealing results. By utilizing proper adhesion testing and considering the three critical factors of UV ink, pre-treatment, and material transparency, you can avoid unsightly scratches and premature flaking. As we’ve all experienced the disappointment of printed designs fading away too soon, it’s crucial to prioritize care and knowledge when selecting materials and printing processes. With the right approach and attention to detail, you can ensure that your digitally decorated UV printed items stand the test of time, providing lasting satisfaction for both you and your customers.