Digital Magazine

Q&A Know Your Films!

With the growth in demand for flexible packaging predicted to continue at a rapid rate for the foreseeable future, Jan Eisby, CSO at surface treatment pioneer Vetaphone A/S, explained why it is so important that printers and converters know exactly what they are dealing with to ensure optimum productivity.

What’s the basic principle behind what you’re doing at Vetaphone?

Eisby: Our company philosophy is based on sharing knowledge, because we believe it empowers people to do a better job.  And because we invented Corona treatment 70 years ago, we have an unrivalled archive of data and expertise that we can use to assist our customers.

Why is it so important to understand the process of Corona treatment?

Eisby: Because it’s all about adhesion and the issues associated with non-absorbent materials, where matching the surface energy of the ink or lacquer to the substrate is essential.  If they don’t match, there will be problems with adhesion, so Corona treatment is the way we change the surface structure of the substrate to ensure good adhesion.  We measure this surface energy in dynes, which is a function of watts of energy applied per square metre per minute.

So really, you need to know your dynes too? 

Eisby: Yes, because all plastic film intended for packaging is surface treated at extrusion, but films change over a period of time, and under different storage or transport conditions, and even from roll to roll of the same substrate because of the action of additives or contamination.  That’s why it’s essential to test it before you use it, and if necessary, re-treat it, because different films are used for different applications and behave differently – it’s a bit of a moving target.

What are the features of packaging films?

Eisby: Most of them are multi-layer because they have specific functions – like preventing contamination in food packaging or guaranteed hygiene for medical applications.  Take a typical coffee pack for example, which is often a multi-layer material.  Corona treatment will be required on the PP surface to allow it to be printed and subsequently have an adhesive applied before laminating it to a metallised film – in every case, we need to know the dyne level and requirement of each layer before we can recommend the power required and operational production speed.

As well as varying from one material to another, do all rolls of the same film behave the same?

Eisby: No, they don’t. Different rolls from the same supplier can behave differently, while supposedly the same material from a different supplier can pose even bigger problems.  Typically, rolls of a particular film that vary significantly in price will do the same in terms of performance.  Lower purchase price normally indicates the need for more power to reach the correct dyne value and a lower running speed, or both.  As with much in life, you get what you pay for! But, of course, you need to know this information in advance, and that’s why testing is so important because it can be the difference between being able to run at 160m/min or 40m/min with the effect that has on the profitability of the job.

I can see why knowledge is so essential - is that why you established the Vetaphone Academy?

Eisby: We felt it was the best way to disseminate information and share our unique experience of surface treatment.  We have 70 years of data going back to the original patent, so it’s likely that we have tested and analysed most combinations of ink, lacquer, and substrate that the packaging sector has ever used – and this information is an invaluable reference point for customers who are experiencing problems or are looking to experiment and develop new products and applications.

I know you are very proud of your testing capabilities at Vetaphone – can you tell us more?

Eisby: We opened our fully functioning Test Lab facility here in Denmark in Summer 2020 – not the best timing with the Covid pandemic maybe but is has proved to be an invaluable resource for the industry.  It allows us to test the performance of any type of packaging film, either in sheet form or on the roll and simulate a real-life production environment.  What it effectively does is take all the guesswork out of the equation and minimise the cost implications for printers and converters in their everyday production scenarios.

What does the new test lab add to your capabilities?

Eisby: For a start it allows us to test on the roll, and secondly it has Plasma as well as Corona capability.  We can switch the type of electrodes and rollers to test differing requirements for customers and closely match their own in-house production capability.  The Test line can be programmed to apply a specified level of Corona treatment to the roll.  The roll can then be tested to see what dyne level has been achieved.  We have now automated this process by adding a label dispenser so that different sections of the roll can be treated using differing power levels and each can be clearly identified by its label and measured for the dyne level achieved.  

Does this all have to take place at the test lab?

Eisby: Not necessarily.  A good way of using the Lab facility is to send us a roll of the film intended for production so that we can apply varying levels of treatment to assess its potential for the concept in mind.  The customer can then test the differently treated sections of the roll in-house to determine which is right for them to use for the job in question in their own commercial environment.  The amount of time and money invested at this stage is insignificant compared with getting it wrong in production – that’s what our unique Test Lab facility brings to the market and why we’re so proud of it.

Are there other tests you can do?

Eisby: We can carry out an Advanced Contact Angle Test that analyses the droplets and gives a highly accurate measurement of the surface energy of the film.  This produces a “wetting envelope” that tells you if you have chosen the correct ink or adhesive for the material being used for the job.  The other capability we have is an Advanced Peel Test that assesses whether the laminate bonding is good or bad.  It measures the force required to tear the product apart and details any issues involved.

NC: How would you summarise your message to printers and converters?

Eisby: The key element is to know exactly what you’re dealing with, so you don’t make expensive mistakes in commercial production.  The best way to do this is to tap into the vast knowledge and expertise that is available from us here at Vetaphone.  We invented Corona surface treatment and have continued to develop the technology – so there’s a lot of useful knowledge that we make available.  Whether it’s testing new ideas or looking to improve efficiency on existing work, we can assist you with our test lab capabilities, and at the same time enrol your employees in our Academy Programme, which provides hands-on skills that are directly transferrable to the production floor.  We’ve always believed that “knowledge is power”, and in today’s complex and competitive marketplace, the better informed you are, the greater your chance of success.