Colour and Chemical Changes of Black Locust Wood during Heat Treatment

Black locust is a fast-growing deciduous tree species with multiple industrial purposes due to its valuable traits. However, the heterogeneity of colour distribution between sapwood and heartwood limits application. Thermal modification an environment-friendly technology for improving various wood properties, especially dimensional stability, decay resistance, homogeneity. In this work, black (Robinia pseudoacacia L.) samples were thermally modified at temperatures 160, 180, 210 °C. Extractives main components analysed by wet chemical methods, was measured spectrometry, structural changes Fourier transform infrared spectroscopy. The obtained results show that darkening wood, unlike other temperate zone, mainly caused in extractives. Their content decreases during thermal treatment, but new chromophores are formed, quinones. Degradation hemicelluloses partial degradation cellulose also contribute changes. At higher temperatures, condensation reactions can occur lignin, leading formation some chromophores. Statistical analysis confirmed temperature be considered very significant factor affecting surface.