Analysis of Photo-Degradation of Dyed Veneer by XRD and SEM

The influence of ultraviolet radiation on photo-degradation of dyed veneer surfaces of Betulacostata Trautv has been examined in this study. Dyed veneer powder specimens were irradiated with a 45-watt UV light source and exposed 100 hours were analyzed and characterized for color, crystallization performance and microstructure changes by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that dyed veneer powder specimens took a remarkable change (photo-discoloration) in color with increasing irradiation time. The lattice structures of crystallite in wood cellulose were not destroyed by UV radiation, and the two theta angles and layer spacing d in crystallite were constant. The relative crystallinity of dyed wood presented an increase at initial period of exposure which decreases upon prolonged exposure, but the change was not apparent, no greater than 3%. Wood microstructure has exhibited obvious deterioration, pit membrane in wood cell walls as well as wood fiber surface stripping phenomena. Analysis of the crystal properties changes and SEM measured indicate that photo-degradation of dyed veneer is mainly due to dye stuffs in prophase and based on wood in anaphase.