Paola Cetera

Machinability of Minor Wooden Species before and after Modification with Thermo-Vacuum Technology

The influence of the thermal modification process on wood machinability was investigated with four minor species of low economic importance. A set of representative experimental samples was machined to the form of disks with sharp and dull tools. The resulting surface quality was visually evaluated by a team of experts according to the American standard procedure ASTM D-1666-87. The objective quantification of the surface quality was also done by means of a three dimensions (3D) surface scanner for the whole range of grain orientations. Visual assessment and 3D surface analysis showed a good agreement in terms of conclusions. The best quality of the wood surface was obtained when machining thermally modified samples. The positive effect of the material modification was apparent when cutting deodar cedar, black pine and black poplar in unfavorable conditions (i.e., against the grain). The difference was much smaller for an easy-machinability specie such as Italian alder. The use of dull tools resulted in the worst surface quality. Thermal modification has shown a very positive effect when machining with dull tools, leading to a relevant increment of the final surface smoothness.

Wettability and Color Change of Thermally Treated Poplar OSB after Accelerated Weathering Test

Oriented strand board (OSB) panels are widely marketed for several applications, from 13 building to packaging. The manufacturing of poplar OSB started recently in Northern Italy 14 representing a relevant innovation in the sector since this product is usually made of coniferous 15 wood. The thermal treatment is widely used for reducing the hygroscopicity of wood-based 16 products, nonetheless it influences the mechanical behavior and degrades the main components of 17 wood, which can affect their finishing. Therefore, it is important to know the properties of the 18 treated surfaces. To this purpose, in this study a lot of OSB panels, made of poplar wood, 15 mm 19 thick and with a density of 590 kg/m3, were thermally treated under vacuum conditions at 190 °C 20 for 2 h and then subjected to accelerated weathering. The changes in color and in wettability due to 21 treatment and accelerated weathering were studied. The thermal treatment determined a 22 significant darkening of the color; the accelerated weathering darkened the untreated surfaces and, 23 on the opposite, lightened the thermo-treated surfaces. The wettability decreased after thermal 24 treatment and increased after weathering, more evidently in treated panels. Overall, this study 25 improves the knowledge about the behavior of the surface of thermo-treated poplar OSB, which is 26 relevant for the industrial coating of this product. 27