Tuesday, November 14, 2023
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Coating is a vast platform. In the wide scenario of the coating materials for furniture surfaces, the last significant technological evolution can be considered that of excimers. Although known to operators in the sector, above all for the performance that the surfaces treated in this way can offer, the theoretical principles on which it is based are probably a little more elusive also due to a certain complexity that actually involves this new technology. However, there is no doubt that a basic knowledge, even if not particularly thorough, is often essential to understand its potential, to deduce its limits but also to deal with any problems that can always arise when using new materials or new technologies.
Let’s have an enlightenment on how excimer coatings precisely offer great technological advancements for surface coating. there are general and practical aspects of this technology.
What are excimer lamp used for?
The very high energy produced by excimer lamps is able to produce very important effects with the substances or surfaces with which it comes into contact, being able to even modify their chemical composition. One of the most common applications is the cleaning and sanitizing of surfaces which take advantage by the combined effect of the molecular degradation of the polluting particles caused by the high energy of the UV radiation and the oxidative effect induced by the ozone that these lamps always produce in presence of oxygen.
Other applications concern the activation of surfaces or their oxidation without entering other fields such as the medical one where these sources are used for very specific applications.
The primary application in the coating panels
In the panel coating sector, excimer lamps have found an interesting application by integrating into systems that use photocurable coating (UV coatings). Excimer lamps are in fact used to produce very matt (low gloss) surfaces without the need to add matting additives to the formulation of liquid coatings.
In traditional products, in fact, these additives which have the form of tiny particles insoluble in the liquid coatings, tend to migrate towards the surface during drying, producing a sort of superficial micro-roughness. The light rays, when they bounce off a surface made in this way, are scattered in all directions, producing the matt sensation to our eyes.
In the case of excimer systems, after an initial gelling of the coating (partial hardening) induced by traditional UV lamps, the surface passes under the excimer lamps which produce a sort of surface wrinkling. In the last phase of the drying process, the coated surface is irradiated again by the traditional UV lamps which complete its hardening. The wrinkling induced by the excimer lamps therefore produces very matt surfaces and the high energy that strikes the coating also induces a very high surface hardness.
Potential advantages and possible disadvantages of excimer technology
The most appreciated advantage of excimer coatings is the possibility of producing very low gloss surfaces, the socalled “zero gloss” to which today’s market is very sensitive.
These low matt surfaces are also very stable to the effect of wear that traditional products suffer much more. The simple cleaning of a surface can in fact remove or smooth out the matting agents that have produced the surface microroughness, causing it to polish with the formation of unsightly patches of varying surface gloss.
In the case of excimer coatings this does not happen also thanks to their very high hardness, much greater than that of any other traditional coating material. The tests to investigate the scratch resistance and the resistance to the contact with liquid substances show, normally, very good results.
On the other hand, other properties deserve more attention, such as the resistance to dirt. The dirt particles can in fact deeply penetrate the previously mentioned micro-roughness of the surface with a certain difficulty in subsequent removal attempts (cleaning). Even the color change should be considered, especially in the case of white surfaces, as it is subject to particular dynamics with possible evidence of yellowing in dark conditions which, in some cases, can also show a sort of subsequent reversibility. These effects are already known for some traditional UV coatings.
At the plant level there are no particular problems related to this technology which must in any case be associated with UV systems, except that of necessarily having to remove the oxygen from the area where the excimer lamps operate. As previously mentioned, these lamps induce the formation of ozone in the presence of oxygen molecules. The plants must
therefore operate in an inert atmosphere with flows of nitrogen generated by suitable systems or in any case stored in special tanks.