Abstract:
The study aimed at treating metil (Sterculia appendiculata K. Schum) and neem (Azadirachta
indica A. Juss) timber from Mozambique under industrial condi- tions by steam [Thermowood®
(TW)] and vacuum [Termo- vuoto (TV)] thermal modifications (TM). Matched boards were
treated identically and wood alterations in chem- istry, colour, mass loss (ML), mechanical
properties and durability were compared. The applied vacuum partly removed the acetic acid that
causes carbohydrate degra- dation, i.e. heat applied under vacuum was less destruc- tive. TM
under vacuum generated a lighter colour than that caused by steam treatment. ML was
significantly higher after the TW process namely, 14.1 vs. 9.9% after thermo- vacuum treatment
for metil and 14.2 and 12.1% for neem. Colour and ML changes correlated with the decrease in
shear strength, rupture and elasticity moduli and increase in wood decay resistance. Metil wood is
more permeable and demonstrated significant differences between the treatments; the thermo-
vacuum process was less destruc- tive but led to less improvement of durability compared to TW
treatment.
