The UV curing (or radiation cure) process describes the use of UV or visible light to trigger the formation of a solid polymer from a mixture containing monomers, oligomers, photoinitiators and additives. The final photopolymer can have a wide range of applications ranging from coatings,adhesives, inks to name a few.
Every component in the formulation has a critical function. Oligomers, for example, are the components responsible for the overall properties of the cured polymer (hardness, flexibility, scratch resistance). The main function of monomers is to serve as a diluents (regulates viscosity) and crosslinkers, photoinitiators are the small molecules responsible for light absorption and generation of the active species that will trigger the crosslinking and finally the additives help to fine tune the performance of the photopolymer.
Along with the components of the formulation, the next most important thing for a successful curing process is the lamp/light source selection. An improper mismatch between the emission wavelength of the lamp and absorption spectrum of the photoinitiator will result in a failed cured or poor cure.
For example, our H-Nu 470 photoinitiator for free radical photopolymerization, displays an absorption max at 470nm. The perfect match will be a lamp or light source which emits light at 470nm or somewhere around it. If you are working with a lamp that emits light in the UV region of the spectrum (200-400nm) most likely the cure process will not take place or you will end up with a gel-like consistency rather than a solid polymer. Needless to say, if the polymer is not properly cured, it will not display the desired properties.
The application, including desired properties of the photopolymer and substrate application, will determine the selection of the oligomers, monomers and additives. In conclusion, in order to produce a successful UV/Visible light curable formulation all components must be considered as a whole unit rather than individual parts.