Varnished surfaces often have to meet both functional and decorative requirements at the same time. Expectations are also increasing here in terms of environmental awareness. UV technology provides the opportunity to combine both environmental compatibility and high performance when it comes to varnish drying, as the following article will show.
According to surface technology experts, UV curing can be counted as one of the three most important technologies of the future ⿿ alongside water-based varnishes and powder coating. The use of UV-cured varnish systems also ensures compliancy with ever stricter EU legislation concerning the environment, as Holder Maier, Sales Manager for Special Applications at UV supplier IST METZ in Nürtingen, explains.
Impressive properties boasted by UV varnishes
It is in the reduction or prevention of VOCs (Volatile Organic Compounds) that UV technology really scores highly. However, UV varnish also delivers an above-average performance with its superb chemical and mechanical properties. High scratch-resistance is one such important advantage with the resistant layer of varnish on, for example, lipstick holders preventing the surface from getting scratched when thrown together with other sharp objects, such as keys, in a handbag.
According to Maier, however, UV technology has even more to offer. It promotes efficiency with high production speeds and swift processing thanks to shorter curing times. Split-second curing also means that the UV varnishing is much less susceptible to contamination when compared to other varnishing systems that often require long drying ovens. When used on machine installations, the UV units also require considerably less space than more conventional drying technologies.
Broad scope of application
With advantages such as these, it is unsurprising that UV varnishing boasts such a wide spectrum of applications. IST METZ has thus already developed numerous UV systems for industrial applications. One example here is the automotive industry, where lenses and reflectors for headlights, trims, steering wheels, wood-effect interiors, wheel hubs and brake pads are varnished or coated using a UV procedure. Another typical application would be the varnishing of plastic parts, i.e. for mobile phones. This extends right up to top coats for display surfaces when a high mechanical strength is required, for example because the phone is operated using a stick. In addition to the cosmetics packaging already mentioned, e.g. lipsticks or spray cans, everyday items such as wall sockets are also coated in UV varnish.
Curing instead of drying
Deciding on UV technology means switching from the conventional drying methods, such as the evaporation of solvents, to the curing of layers by means of polymerisation. Expert knowledge is thus required here for the correct integration of the new technology into production processes. This poses a number of specific questions, such as what will happen with the overspray, how to dispose of the varnish, can excess UV varnish be recovered and which housing will safely shield the UV lamp?
In order to effectively use UV technology over the long term, Holger Maier recommends regular cleaning and maintenance. Contamination of lamps and reflectors can lead to unnecessary output losses. The UV system can be coordinated with specific applications when doped with, for example, gallium or ferrous material. Regulation of the air cooling via temperature and volume secures constant operating conditions irrespective of performance.
Generally speaking, there are still plenty of opportunities for the further development of UV technology in the realm of industrial applications. Holger Maier thus sees the widely discussed topic of LED UV technology, for which IST METZ has designed its own UV system, as becoming less of a short-term focus for the industrial sector. Instead, he sees further progress being made on new units that work with, for example, optimised reflector geometry.
