Density profile and micromorphology variation of densified wood from three fast growth hardwood species in Costa Rica
Keywords:
THM densification, vessels, temperature, tropical speciesAbstract
This study evaluates 1) the effect of the thermo-hydro-mechanical densification process-using three temperatures, two compression times, and the presence or absence of steam, and 2) the effect of initial wood micromorphology on the density profile of densified wood of three low-density fast growing hardwood species in Costa Rica (Alnus acuminate, Vochysia ferruginea, and Vochysia guatemalensis). Four density profiles in the densified wood of the three species resulted from the densification temperature and the initial micromorphology of the wood. The initial diameter of the vessels affects the compression stage during the densification process and causes the formation of irregular density profiles. Therefore, this is the most important element in determining the type of the density profile. The wood of A. Acuminata (with smaller-diameter vessels) densified at 180oC tends to produce more uniform density profiles than the other two species that have larger diameter vessels. The time of compression and the use or not of steam as an initial stage in the densification process did not influence the types of density profiles obtained. Similarly, the type of wood tissue and wood pattern had no effect on the type of density profiles. In conclusion, uniform and regular density profiles in densified wood are more likely to be achieve at high temperatures and with smaller-diameter vessels.
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