Photodegradation of wood at elevated temperature: colour change.

The purpose of this investigation was to evaluate the effect of elevated temperature on the photodegradation of solid wood. The work presented here, dealt with the changes of colour during the degradation process. Wood samples were irradiated by mercury vapour lamp at 80°C and at 30°C to screen out the effect of thermal decomposition during photodegradation. Results demonstrated that the same light irradiation resulted in considerably greater redness increase at 80°C than at 30°C. Pine samples showed 57% higher redness change at 80°C than at 30°C during the 200h light exposure. Corresponding data for spruce, ash and poplar were 33%, 40% and 15%, respectively. Results indicated that the extractive content has an important role in thermal decomposition during photodegradation. The elevated environmental temperature did not affect yellowness.