Chemistry of wood
Mohadeseh Hosseini Someah; Mehrnaz Azadi Boyaghchi; Kambiz Pourtahmasi; Maryam Afsharpour; Samad Nejad Ebrahimi
Abstract
Background and Objectives: Historical papers identification is one of the important stages of studying archival and paper works to ensure its proper conservation. Historical papers consist of fibers with organic carbohydrate compounds such as cellulose and hemicelluloses and lignin. In this identification ...
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Background and Objectives: Historical papers identification is one of the important stages of studying archival and paper works to ensure its proper conservation. Historical papers consist of fibers with organic carbohydrate compounds such as cellulose and hemicelluloses and lignin. In this identification method, the main values mentioned are evaluated and calculated based on the data points and the resulting fraction of the intensity of these main compounds. However, there are components such as lignin in the internal structure and starch in the external structure of historical papers that over time not only lead to damage but are also effective in identification with this method. Many instrumental methods have been used to identify historical papers, including infrared spectroscopy. This research aims to investigate the effect of aging and sizing changes on two types of historical papers known as Samarqand and Daulatabad papers with this device method.
Materials and methods: Among the historical papers, 8 samples were randomly selected. These samples were all selected with the characteristics of self-color and the same starch sizing content, which were measured using Logel's test for this purpose. Artificial aging test was used to investigate the changes in the internal structure of papers as well as the stains on the surface of historical papers, which is an accelerated method of destroying the molecular structure of organic materials of paper. To prepare the samples, about 5 g of historical paper samples D2 and S4 were removed and placed for 24 hours at 23°C and 50% relative humidity. Then they were transferred to the incubator for 24 days for accelerated aging test at 80°C temperature and 65% relative humidity. FTIR Spectroscopy was used in Tehran Art University. This model device is TENSOR 27 made by Bruker, Germany with ZnSe crystal analyzer surface and attenuated total reflection method in the range of 400 cm-1 to 4000 cm-1.
Results: After two cycle of 12 days (576 hours and approximately equivalent to 50 years), the
acidity values in two historical paper samples show a decrease in the pH number value. These values reveal the oxidation of cellulose, which is caused by the combined process of thermal and moisture accelerated aging. The results of increasing the acidity of the papers showed clear peaks in the region of 1730 cm-1 or increased their intensity. These absorption bands correspond to C=O bonds in the carbonyl groups, which were absent compared to the samples before aging and became apparent after aging. The comparison between two historical papers aged for 50 years more than the original paper samples in FTIR-ATR spectroscopy show that after aging, the intensity of cellulose and organic compounds has decreased compared to lignin and with the increase of lignin peak intensity in the region 1595 cm -1 has revealed itself. And these two samples are placed at a higher and farther height compared to their original paper samples, which is due to the increase in the amount of lignin compared to the amount of cellulose and organic compounds. Therefore, the role of aging and change of acidity in the change of fiber identification points according to the Garside diagram is wrong. Also, the effect of the external factor of starch is also shown by the change in wave numbers and their intensity in the main points of 1595 cm-1, 1105 cm-1 and 2900 cm-1. In the spectroscopy of the original paper, the reduction of the peak intensity is quite evident, and this shows that the starch sizing has led to the covering of the paper surface and ultimately the reduction of the intensity of the spectrum. Therefore, by washing the papers, the intensity has changed and the amount of lignin has decreased slightly, but the measure of organic compounds and cellulose has increased.
Conclusion: The result showed that the amount of acidity that appears with the increase of age and with the increase of lignin in historical papers has an effect on the intensity points obtained from FTIR-ATR spectroscopy and shifts them in the Garside diagram. Also, starch sizing is another factor that plays a significant role in changing the data of the Garside diagram in the identification of historical paper fibers and they show different points. Therefore, starch sizing and the aging process, which is related to the change in the amount of acidification of historical papers, affect the FTIR-ATR spectroscopy.
