[FTIR spectroscopic studies of the photo-discoloration of Chinese fir].
Wood or wood products undergo rapid degradation of surface characteristics and quality indicated by changes in wood color during outdoor exposure owing to a combination of various weathering factors, which may result in significant reduction in utilization values of wood. In the present study, photodegradation of wood surfaces of Chinese fir (Cunninghamia lanceolata) was carried out by a Xenon test chamber which can simulate sunlight irradiation. A Fourier transform infrared (FTIR) spectroscopy technique was used to study chemical changes caused by irradiation during photo-discoloration of wood surfaces, and the relationship between the changes in color and chemical composition was established. Results indicated that, during the process of irradiation, the intensity of absorption bands at 1512, 1462, 1269 and 1227 cm(-1) decreased significantly, accompanied by a successive increase in the intensity of band at 1720-1735 cm(-1). Lignin was the most sensitive component to the degradation process and underwent severe photodegradation during the process of irradiation. This was accompanied by formation of new carbonyl compounds, which indicated the photo-oxidation of wood surfaces. In the initial 80 h of irradiation, the degradation of lignin and formation of carbonyl groups were intense, and then became insignificant in longer exposure duration. Degradation of polysaccharides (cellulose and hemicellulose)also occurred during the process. Overall, color changes (deltaE*) were correlated well with the degradation of lignin and relative increase in the content of carbonyl groups during the process of irradiation.
Wang
Xiao-qing
XQ
Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China. wxqlily@yahoo.com.cn
Fei
Ben-hua
BH
Ren
Hai-qing
HQ