Effects of UV Radiation on Paper: A Chromatic Study

Abstract

A study on Whatman #1, bond, rice, kraft, and amate papers in their original condition and exposed to 2.25, 4.5, 6.75, and 9 W of Ultraviolet-C radiation is presented. The techniques used were scanning electron microscopy+energy dispersive X-ray spectrometry (SEM+EDS), differential scanning calorimetry+thermogravimetric analysis (DTC+TGA), Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), Ultraviolet/Visible (UV/Vis) spectrophotometry, pH measurements, and colorimetry. No changes were found in these papers, length and width of fibers, chemical composition, pH, pyrolysis characteristics, or FTIR and XRD patterns after irradiation. Cellulose (all papers), calcite (bond, rice, and kraft), whewellite (amate), and kaolinite (kraft) were the main components. Non-irradiated bond paper showed a specular effect on the UV spectra, which was progressively reduced by the UV radiation and becoming almost imperceptible at >6 W. Visible spectra of amate paper showed the presence of β carotenoids and chlorophylls, which are degraded by UV radiation. Visible spectra of Kraft paper showed a color reversion at 2.25 W, which progressively diminished as a function of the UV rate energy transfer. UV radiation gradually clarified amate paper. To make a comparison, kraft and amate paper were exposed to gamma radiation at 3, 9, and 15 kGy. The color of Kraft paper was clarified, and amate paper increased in yellowness. Perceptions of chromatic differences due to gamma radiation were smaller than those observed with UV radiation; however, they are still important, especially for kraft paper.