Dissertations in Forestry and Natural Sciences

Taneli Väisänen: Effects of Thermally Extracted Wood Distillates on
the Characteristics of Wood-Plastic Composites
in the emission rates. Therefore, the results suggested that furan
does not contribute any major effects to the VOC characteristics
of WPCs. Guaiacol was also emitted to a low extent, but it is
possible that it can be smelled from WPCs due to its low odor
threshold.
Furfural was emitted most abundantly in the beginning of
the trial. However, as the trial continued, the emission rates of
furfural decreased continuously. Previously, the emissions of
furfural from heat-treated wood species have been investigated
by Hyttinen et al. (2010). They demonstrated that heat treatment
caused the formation and higher emissions of furfural. In
contrast to the present findings, the emission rates of furfural
did not decline during the test period in their study – in contrast,
the emission behavior of furfural resembled that of acetic acid.
Furfural is formed from the degradation of hemicelluloses and
cellulose, and therefore, it is possible that the degradation
process had continued in the wood samples during the
measurements. The inconsistent emissions rates may be caused
by the uneven diffusion of furfural. The plastic matrix in WPCs
may decelerate the diffusion of furfural from the inside of the
material to the surface, and therefore, the detected emission
rates constantly declined.
Monoterpenes, such as - and -pinene, are abundant in
wood (Roffael et al. 2015). They have a pleasant resinous aroma
with pine-like odors, are highly repellant to insects and possess
antioxidative properties (Goldstein 2002, Nerio et al. 2010, Silva
et al. 2012). Monoterpenes do not cause major changes in the
respiratory tract or lung function, but they have evoked chronic
reactions in the airways (Eriksson and Levin 1990, Falk et al.
1990, Eriksson et al. 1997). The presence of monoterpenes is
therefore permissible only to a certain extent. Monoterpene
emission rates decreased during the trial. Yrieix et al. (2010) also
observed a decrease in the monoterpene emissions from their
wood-based panels. Similarly, Roffael (2006) reported
decreasing emission rates for monoterpenes from wood.
LunaComp decks, that have thermally modified sawdust as
a reinforcement material, had the lowest VOC emission rates in
106 Dissertations in Forestry and Natural Sciences No 222