In general UV-curable substances include three groups of reactive materials:
- Monomers or Cross-linkers
- Oligomers (also called resins)
In addition to these components UV coating, UV printing inks and UV adhesive may also be combined with the usual additives, fillers and pigments as well as other ingredients. These components do not usually have any UV reactivity and will not polymerise like the reactive materials.
Monomers or Cross linkers are used to dissolve the resins and to adjust viscosity and the degree of cross linking of the UV systems.
Resins or Oligomers are responsible for the properties of the cured UV coating, UV printing ink or UV adhesive, for example scratch resistance, flexibility, elasticity, adhesion to different substrates and so on.
Photoinitiators are the most important component in UV curable systems; no UV curing can take place without photoinitiators or UV sensitive materials!
When irradiated with UV, photoinitiators generate so called „free radicals“; these reactive particles are responsible for setting further polymerisation in train.