Influence of thermal treatment on selected properties of chestnut wood and full range of its visual features

The use of chestnut wood (Castanea sativa Mill.) is highly relevant in Central Italy, as it is one of the most important and abundant broad-leaf species in this geographical area. The comprehension of the modifications induced by thermal treatment is of crucial importance to define the optimal temperature that could improve the mechanical and physical properties without affecting significantly the visual appearance. In this paper a careful and complete investigation on the effect of thermal treatment on chestnut wood (Castanea sativa Mill.) is reported. The aim of this study is addressed to understand the chemical-physical modifications occurred on the surface of wood samples, as a consequence of heating, in order to choose the most suitable temperature of treatment, also in the view of applying a possible coating. No such complete and homogeneous study on chestnut wood was found in the literature, so this paper contributes to add relevant scientific and technological information on it. Samples of chestnut were thermally treated 6 hours in a conventional oven at 140°C, 170°C and 200°C. Surface properties of heated wood, in comparison with untreated, were evaluated through the measurements of: roughness, colour, Vickers and Brinell hardness, surface profile and contact angle. The behaviour of earlywood and latewood was evaluated by studying separately the effect of heating on contact angle and surface micro--hardness. Fourier transform infrared spectroscopy was also used to evaluate the chemical modification of wood components due to thermal treatment. Heating at 140°C has little influence on wood characteristics whereas 200°C has a great impact on colour, mechanical properties and hydrophobicity behaviour. The intermediate temperature, i.e. 170°C, seems to give the best results in term of improved mechanical properties and also aesthetical appearance of wood surfaces