Photoyellowing revisited: Determination of an action spectrum of newspaper

Improved methodology for deriving action spectrum of photoyellowing induced by UV radiation on a polymeric material is reported. Facility designed and constructed for exposing materials with narrow-band UV radiation has been used for ageing newspaper samples for time periods of 1, 2, 4, and 8 h. Radiometric characterization of the facility has been utilized for defining the radiant exposure onto the samples during the exposures. Yellowing of samples has been quantified by post-exposure colour measurements. The relation between the quantified property change and the radiant exposure has been modelled. The analysis accounts for the logarithmic temporal behaviour of the property change and yields a generic material specific action spectrum for photoyellowing.