بررسی تغییرات شیمیایی و‌ ساختار میکروسکوپی چوب راش طی فرآیند‌ هوازدگی

In this study Beech wood (Fagus orientalis Lipsky) samples with dimentions of 150755 mm were prepared and subjected to a variety of artificial weathering conditions in an Atlas Xenon Test Beta LM Weatherometer to UV radiation (300 nm) and visible light (750 nm) and water spray in different times (50, 150 and 300 h). Then wood surface was analyzed for chemical and structural changes using Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM), respectively. Results showed that weathering process affected the functional groups on the wood surface. Full weathering (light and water) damaged the surface polymer structure and caused chemical and physical changes in wood. The greatest changes occurred in the functional groups and aromatic structure of lignin. With increasing of weathering time, the absorption intensity of c=o loonds increased at 1730-1740 cm-1 and aromatic skeletal vibration in intensity 1514 cm-1 decreased. By the effect of UV radiation, choromophoric groups were produced in lignin. Photochemical cleavage of C-C bonds adjacent to carbonyl groups made the chemical compounds smaller and water-soluble. The SEM results showed that the surface of wood exposed to weathering undergoes distinct physical changes and the surface degradation appears to be directly proportional to the time of exposure to the weathering conditions. However, trace changes were observed in samples weathered for 50h.