| Abstract: | The study investigated and compared the behaviour of four wood species, originating from Europe and China, in terms of temperature-induced artificial ageing. It was conducted at 100 °C for a total period of 288 h. Ageing effects were evaluated by colour measurements in the CIE Lab system and by FTIR analysis. Colour changes were then related to chemical changes in the wood. The investigated wood species were European ash (Fraxinus excelsior), European walnut (Juglans regia), Chinese ash (Fraxinus mandshurica) and Chinese walnut (Juglans mandshurica). Colour changes were maximum for European ash and minimum for Chinese ash, while European walnut and Chinese walnut evolved quite similarly. Main chemical changes due to temperature ageing were reduction of hydroxyl groups, increase of the unconjugated carbonyl groups and an apparent slight increase of lignin, more evident for European ash and delayed for European walnut. Formation of aromatic carbonyl conjugated groups as quinoid structures as a result of oxidative reactions was revealed especially for European ash. The different behaviour of the studied wood species may be explained by their different chemical composition, especially hemicelluloses, lignin and extractives content. |
