Surface degradation of wood by ultraviolet light

Abstract Wood is beautiful but sensitive to light. Because of the chromophoric system at its surface, ultraviolet light cannot penetrate it deeper than 80 μm. Surface characteristics of ultraviolettreated wood were analyzed by infrared and ultraviolet spectroscopy. Analyses of infrared spectra revealed that ultraviolet‐treated wood is rich in carboxylic and carbonyl chromophoric groups and poor in aromatic functional groups. Ultraviolet spectral studies suggest that water‐soluble low molecular weight fractions of degraded products from the wood surface are mainly derived from lignin. These degradation products contained carbonyl conjugated phenolic hydroxyl groups and had a weight‐average molecular weight of about 900, confirmed by gel permeation chromatography.