by photoinitiated radical chain polymerisation.
Photopolymerisation is the process of converting
a liquid monomer to a solid polymer by
using ultraviolet radiation. This photochemical
process starts by the absorption of ultraviolet
light by a photosensitive chemical compound
(photoinitiator). The photoinitiator then starts
the polymerisation process by producing free
radicals. Free radicals are highly reactive species,
like electrons, anions or cations, which break
up carbon-carbon double bonds (C=C bonds) in
molecules in the monomer that undergoes polymerisation.
By this process of destroying carboncarbon
double bonds, the molecule itself becomes
highly reactive and links itself to another highly
reactive molecule. By this forming of very long
macromolecules the liquid monomer changes to
a solid polymer that can have totally different
properties from the liquid monomer. The speed
of the polymerisation process is highly dependent
on the number of free radicals that the photoinitiator
provides by dissociation under ultraviolet
radiation.