As in any industrial process, problems may also occur in UV curing through incorrect handling.
One of the main problems is the so-called ,, oxygen inhibition“.
The oxygen inhibition effect is only a problem in free radical UV systems.
Oxygen inhibition means that oxygen, a very reactive gas, also reacts very quickly with free radicals formed from acrylate double bond systems after the reaction between oxygen and these free radicals stops the polymerisation process at the surface of the coating or printing ink.
In consequence the coating or printing ink will remain tacky on the surface, while deeper layers have cured properly. Properties like scratch resistance and chemical resistance will be dramatically reduced.
The solution to these problems is UV curing under inert conditions; i.e. curing under inert gases (excluding the presence of oxygen). Inert gases are chemicals that do not react with other components of the coating or ink.
Inert gases are for example:
- Helium, Neon, Xenon or Krypton
- Carbon dioxide
In many applications UV curing of coatings and inks is only possible under inert conditions.