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Radiation Curing has proved to be an efficient method to provide polymeric layers by
exposing liquid systems to UV or EB radiation. Besides the absence of non-reactive volatile
solvents (VOCs) still used in many coatings, printing inks and impregnants it is the advantage
to gain a 100 % conversion of suitable systems within fractions of a second. Besides
sophisticated methods in research laboratories to follow the stages of cure towards the
desired complete conversion, under manufacturing conditions these techniques often lack an
easy applicability and usually cannot be defmed as non-destructive testing. A reasonable
method using the decrease in intensity of JR-bands attributed to the double bonds faces
some practical problems under manufacturing conditions. Acrylic esters usually offer
three bands to evaluate (Fig. 1+2, 1630 nm, 1410 nm, 810 nm) but as shown later in this
paper not all of them guarantee suitable results like the 810 nm in Fig. 3 as it is sometimes
difficult to draw a reliable baseline or the bands find themselves on the shoulder of a much
greater band. Commercial production lines are often operated at or near limit parameters,
below which an insufficient extent of cure might result, thus an easy access to information
about the cure status is of increasing importance. Besides the problems created by any components not being incorporated by crosslinking and thus migrating to the surface residual
double bonds are photoreactive centres and might be responsible for a reduced lifetime of
the products due to degradation processes. Though this method has been investigated for
radiation curable systems it might be also applied for systems cured by heat and/or catalyst.
