The degree of cure of the coatings should be known for quality control and design of the curing system. Often
the radiation part of the curing installation is oversized, because the spectral irradiances needed for a certain
conversion of carbon double bonds were not determined beforehand. The usual testing methods for the quality
of a coating, as for instance ATR spectroscopy, are only sensitive to the attributes of the surface. In our
investigations, we measured the degree of conversion locally at different depths of the layer by means of confocal
Raman spectroscopy with a spatial resolution of approximately 1&mgr;m. For the kinetic studies, we measured the
change of Raman scattering of 532 nm Laser radiation. Which induces a transition on a vibration level of the
carbon double bond corresponding to a wavenumber of 1620 cm-1. The change was normalized with respect
to the CH2 deformation mode. Furthermore, we investigated the effect of different spectral distributions of
radiation on the local conversion at different depths. By this it could be shown that most of the radiation power
is needed to harden the surface. This is caused by the inhibiting effect of oxygen which hinders the generation of
radicals. The measured depth profile of conversion reveals that oxygen is effective up to depths of 30 &mgr;m. The
results of confocal Raman spectroscopy could also be used to optimize a curing system with inertization so that
the radiation power could by reduced by 91%.
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