MONITORING OF THE PHOTODEGRADATION OF WOOD BY QUANTITATIVE DRIFT SPECTROSCOPY

Wood of locust (Robinia pseudoacacia) and poplar (Populus tremoloides) tree has been irradiated with 830 W/m2 energy up to 60 hrs and extracted with water in order to simulate outdoor weathering. The progress of weathering was monitored by DRIFT spectroscopy. The spectra were baseline corrected and normalized. Spectral differences with regard to wood species, irradiation time, and water extraction were clearly seen. Very pronounced is the intensity decrease of the bands of aromatic skeletal vibrations at 1510 and 1600 cm-1 and the increase of the band at 17.4 cm-1 (C=O stretching). These changes can be quantified and described by exponential equations. The degradation products of weathering are of low molecular weight and can be eliminated from the wood surface by water extraction. The differences between the DRIFT and KBr-TR spectra as well as the quantitative results of the artifical weathering are discussed.