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Bustos Avila, C., Gacitúa Escobar, W., Cloutier, A., Fang, C.-H., and Valenzuela Carrasco, P. (2012). "Densification of wood veneers combined with oil-heat treatment. Part III: Cell wall mechanical properties determined by nanoindentation," BioRes. 7(2), 1525-1532.

Abstract

Compression under the effect of heat and steam, also called thermo-hygromechanical (THM) densification, can increase wood density and therefore improve its strength, stiffness, and hardness. Oil-heat treatment (OHT) is also known to reduce wood’s hygroscopicity and improve dimensional stability. A combination of both treatments can therefore produce wood with improved mechanical properties and dimensional stability. The objective of this project was to determine cell wall mechanical properties of THM-densified and OHT wood. Trembling aspen veneers were densified by a THM process and subsequently treated in canola oil at 200 and 220°C. Nanoindentations were performed in earlywood cell walls. The results show that cell wall longitudinal modulus of elasticity increased significantly from 13.5 GPa for the control to a maximum of 18.2 GPa for THM densified wood with or without OHT. Cell wall hardness increased from 0.27 GPa to a maximum of 0.43 GPa. Both THM densification and OHT significantly increased cell wall hardness. Therefore, the increase in mechanical properties of THM-densified and OHT wood can be due to an increase in wood density resulting from a reduction in porosity but also to an increase in the mechanical properties of the cell wall.
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