Film and Foil Knowing your substrates
In the second of three articles, Jan Eisby, chief business off icer at Vetaphone A/S, the company that invented Corona treatment, explains why knowing the substrates you are dealing with is a key element to success.
W
ith the growth in demand for flexible packaging predicted to continue at a rapid rate for the foreseeable future, it is
important that printers and converters know exactly what substrates they are dealing with to ensure optimum productivity. As I explained in my previous article, surface treatment, usually Corona, is 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. Corona treatment is how 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 meter per minute. It is important to understand this because all plastic film intended for packaging is surface treated at extrusion. Films change over a period and under different storage or transport conditions, even from roll to roll of the same substrate because of the action
of additives or contamination. That is why it is 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 is a bit of a moving target! Most modern packaging films are multi- layer because they have multi functions like preventing contamination in food packaging or guaranteed hygiene for medical applications. A typical coffee pack, for example, 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 metalised 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.
To add another variable into the equation, 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! Of course, you need to know this information in advance and that is why testing is so important because it can be the difference between being able to run at 1000ft/min or 100ft/min with the effect that has on the profitability of the job.
As the inventors of Corona treatment, we have more than 70 years of data going back to the original patent, so it is likely that we have tested and analysed most combinations of ink, lacquer and substrate that the packaging sector has ever used; this information is an invaluable reference point for customers who are experiencing problems or are looking to experiment and develop new products and applications. This is why we say that it is so important to know your films so that you understand ‘shelf-life’, but more about that next time!
12
September 2024
www.convertermag.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58
