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Radiation curing is considered to be the most environmentally friendly technology for the
polymerisation of films, due to the limited use of energy involved in the curing process and
to the limited amount of volatile organic compounds (VOC) employed in the process.
Though the release of VOC in the radiation curing process is several orders of magnitude
lower than in the conventional methods, some concerns have been raised for the release of
benzaldehyde generated in the photochemical decomposition of some photoinitiators( 1), in
particular of the class of ct-hydroxyketones. In fact it is well know that the a-cleavage
process of a-hydroxyketones gives rise to two radicals, that can further evolve to
aldehydic derivatives(2): in particular alkylhydroxyphenones evolve to benzaldehyde that,
due to its very low odour threshold (0.8 ug/m3)(3,4), produces a very unpleasant smell.
Several papers have been published on the evaluation of benzaldehyde from the UV cured
film(5,6). The first author used the chamber method where the cured samples were placed,
while the second employed a cured veneer put into a tube. In both cases the VOCs were
collected under flow of nitrogen onto suitable absorbing medium (activated charcoal,
Tenax) after long conditioning of the cured products. The released compounds were
suitably extracted and analysed by GC or GC-MS. The reported methods are time
consuming and not suitable for a rapid screening of different photoinitiators.
We developed a new easy and rapid technique for the direct evaluation of VOC during the
radiation curing process and we used this method for the evaluation of released
benzaldehyde from commercially available a-hydroxyketones in the curing process.
