The Principle of Irradiation Curing

While the UV systems technology and the appropriate chemistry have been developing continuously, the principle of irradiation curing has widely remained unchanged: High-energy UV irradiation causes chemical curing of UV reactive coatings within seconds.

UV-Spektrum

The short-wave, high-energy UV irradiation in the spectrum between 200nm and 400nm is able to convert a liquid UV reactive substance into a solid film within a split second.

UV range Wavelength
[nm]
Photon energy
[eV]
Characteristics Field of
application
visible light 780 - 380 1,60 - 3,26 adhesives
UV-A 380 - 315 3,26 - 3,94 deep curing inks or coatings
UV-B 315 - 280 3,94 - 4,43 varnishes
UV-C 280 - 200 4,43 - 6,20 surface curing sterilization
V-UV 200 - 100 6,20 - 12,4 absorption
by O
2
no application
for UV curing

Chemical curing

Contrary to a thermal drying process, which works by evaporating the solvent contained in the coating, curing initiates a chemical reaction within the coating compound, which leads to a polymerization reaction.

thermal curing and UV curing

As soon as the reaction is activated by the UV irradiation the ?uid layer “cross-links” to an inert flm within a split-second. The majority of UV coatings offer a 100% coating residual, i.e. they cure almost without loss of coat thickness or VOCemissions.

The irradiation-sensitive element of the coating formulation is the photo initiator. In?uenced by the UV irradiation, the photo initiator - at a radical polymerization - forms free radicals, which are able to split the double bonds within the oligomeres and monomers. This is the start of a polymerization reaction, which transforms the ?uid varnish flm into a three-dimensional structure.

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