Artificial aging paper to assess long-term effects of conservative treatment. Monitoring by infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and energy dispersive X-ray fluorescence (EDXRF)

Abstract

The long-term performance of the conservation–restoration treatment applied in Moroccan libraries has been questioned, to predict and rank the behavior of restored papers under extreme conditions of storage. This study was conducted to assess the effect of aging on the restoration process, in particular the aqueous de-acidification treatment. For this purpose, dry heat (at 90±2°C) and moist heat (100% of relative humidity and 90±2°C) accelerated aging tests were performed for 1, 3, 7, 21, and 28days. Fifty samples taken from four restored Moroccan manuscript papers dating to the 16th, 17th, 18th, and 19th centuries including the Japanese paper used for restoration were artificially weathered. A three-analytical approach has been selected to monitor the effects of weathering on paper components by comparing the results of virgin and artificially aged samples; the diagnosis approach is based on the use of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and energy dispersive X-ray fluorescence spectrometry (EDXRF). ATR-FTIR spectroscopy allowed us to identify the major structural modifications of cellulose, including the alteration of the hydrogen bond network (3000–3600cm−1 region) and the desorption of paper residual water content indicated by the decline of the band at 1641–1647cm−1 in the dry heat aged samples. The oxidation of cellulose is the dominant mechanism of alteration during the moist heat process. It was shown that the crystallinity of cellulose is reduced as the bands at 1425, 1370, and 900cm−1 significantly decreased. XRD was used to compare the crystal phase of un-aged and aged papers and the results showed a remarkable decline in cellulose crystallinity, as evidenced by the strong decrease of crystalline index (CrI%) calculated after artificial aging. EDXRF results showed that both artificial aging tests affected the paper elemental composition, especially in what concerns Ca amount, although not for all aged papers.