Nondestructive evaluation of wood chemical compounds used in Gorgan historical building via FT-IR spectroscopy

Introduction: The use of infrared spectroscopy to describe the lignocellulosic materials has increased dramatically. Since the infrared Fourier transform (FT-IR) spectroscopy least destruction occurs in the test sample and with a small quantity of sample accurate information is obtained, so this spectrometer is a useful technique for identifying chemical compounds of wood. In studying the historic woods, to describe the amount and type of damage to select the appropriate protection method, often FT-IR technique is used. In this study, changes in the chemical compounds of wood used in historical building of Gorgan with healthy species are studied with the help of this spectroscopy.
Materials and Methods: In this study, historic wood samples were prepared from two buildings in the old context of Gorgan (Tekye, Estarabadi and Hosseinieh). Five samples were selected from these two buildings and to identify the species To study Macroscopic characterization to review these woods. Spectroscopy of samples was obtained with the use of MB-154 Bomem FT-IR model. For this purpose, wood flour was prepared from samples from a drill equipped with a drill bit with 3 mm diameter and a depth of 2-3 mm. Flour obtained for the FT-IR test was dried in the oven at temperature 103° C for 24 hours to have the lowest moisture content. Then KBr tablet of the above examples was prepared for the FT-IR spectroscopy test in the spectral range 4000-500 cm-1 and spectral resolution 4 cm-1. 11 scans were performed for each test and samples were compared with healthy samples.
Results: Samples include four species: hardwood (hornbeam, oak, beech, elm) and a softwood species (yew). In all hardwood species, the absorption intensity in areas 897, 1049, 1118, 1160 cm-1 and related to carbohydrates and also bands 1739, 1243 cm-1 in connection with the hemicellulose was reduced significantly. In contrast, in the case of bands related to lignin, poor absorption is seen in 1654, 1595, 1508 cm-1. In Yew species, areas 1608, 1512, 1428, 1273 cm-1 and in connection with lignin and area 1736 cm-1 related to hemicellulose showed a large decrease in absorption.
Conclusion: The results from spectroscopy showed that biodegrades has occurred in all historical species. With relative comparison of changes in intensity of the bands associated with lignin and carbohydrates in hardwood species, it has become clear that carbohydrates degradation was more than lignin, which can be primarily attributed to brown rot. In softwood species (yew), because they have the most contact with the continuous rains, in addition to carbohydrates, lignin has also been destroyed.