From the outside, you can hardly tell the difference between a corona treatment station and a flair treatment station – no additional hood, no additional gas supply, everything is almost identical.

However, the balance of the three key aspects, firstly the molecular weight or length of the polymer molecule, secondly the HSP (or, to simplify, at least the surface tension) and thirdly the crystallinity, actually the amorphous sections of the polymer, is very different between corona and flair.

As described, there is an optimum or limit in the corona process: with the right amount of chain separation, the surface tension is still too low and for enough surface tension, there is already too much chain separation.

This balance is difficult to achieve and makes it almost impossible to achieve good adhesion.

With the flair process, on the other hand, this balance can be found very well, the optimum treatment window is very large and wide and very good adhesion effects can be achieved.

The significance of these physical relationships in practice is shown in the overview in Figure 6.

It’s tempting to say: “Forget Corona, take Flair…”

However, this would not be useful in practice.

For one thing, the corona process is well established, and for another, the surface tension and adhesion it achieves is often sufficient for further processing. There is often no real need to strive for even higher values. Of course, “a little more” would always be better, a slightly higher surface tension, a slightly longer-lasting treatment effect (higher storage stability), but this does not significantly improve adhesion.

And that is usually the case. That’s why we at Plasmawerk mainly supply corona systems – up to 12 m wide and possibly up to 1000 m / min fast, but of course also somewhat narrower and somewhat slower, depending on the technical requirements.

However, if this is not the case or if a higher adhesion is required, then the corona process is not sufficient.

For the one, in terms of storage stability of the treatment effect. We have already mentioned this in previous articles.

And secondly, in terms of improving the adhesion properties.

Just a brief comment on this aspect: In current practice, an intermediate step, priming or a topcoat, helps. A substance, usually in liquid form, is applied to the corona-pretreated surface to act as a bonding agent – like an adhesive. Such enhancers or primers are available on the market in very, very large quantities, depending on the substrate and coating.

However, Flair offers a very “elegant” alternative for achieving higher adhesion values.

Elegant because no additional chemical substances, gaseous or liquid, are required. But unfortunately, Flair is not a one-size-fits-all solution.

It is important to point out here that good compatibility must be established between the substrate or film and the respective coating or print. We described this with the HSP parameters in our first article.

Such compatibility has almost always been achieved for the corona process, as it has now been used for over 60 years.

The flair method, on the other hand, is still an innovation and accordingly this compatibility has not always been established. Same as with priming, this good compatibility must also be found in each case with flair. This is sometimes time-consuming and a demanding challenge for professionals.

However, compared to “classic” priming processes, it is significantly less time-consuming because no liquid substances are required to be applied.

In addition, the Flair process is also very well suited for integration into an existing system as an extension or addition due to its very compact geometry.

In summary, it can be said that

PS: If you would like to find out more, we recommend our presentations on these topics. Please do not hesitate to contact us.