Chemical changes of steamed timber during short-term photodegradation monitored by FTIR spectroscopy

Black locust (Robinia pseudoacacia L.), beech (Fagus sylvatica L.), poplar (Populus x euramericana cv. pannonia) and spruce (Picea abies Karst.) wood samples were treated in saturated steam at 100, 110 and 120 °C for 2 days. Steamed and unsteamed (control) specimens were irradiated using a UV emitter mercury lamp in order to determine the chemical changes generated by UV irradiation. The main goal of the research was to find out if steaming can improve the UV resistance of wood. Chemical changes were determined by diffuse reflectance FTIR spectroscopy. Steaming deacetylated the hemicellulose molecules of hardwood species. Steamed spruce specimens showed the same photodegradation properties as the unsteamed ones. Steaming reduced the photodegradation sensitivity of lignin considerably for black locust only. Steamed hardwood specimens presented greater absorption increase at 1705 cm−1 compared to unsteamed samples, which corresponds to the photodegradation of hemicelluloses.