Dissertations in Forestry and Natural Sciences

esistance of the WPCs with wood distillates. Furthermore, the
applicability of proton-transfer-reaction time-of-flight massspectrometry
(PTR-TOF-MS) in determining the VOC emission
characteristics of WPCs was studied. The effects of incorporating
hardwood and softwood distillates into WPCs were examined by
characterizing the mechanical properties, water resistance and VOC
emissions of these WPCs modified with the distillates. The distillate
content varied from 1 wt% to 20 wt%. The suitability of PTR-TOF-MS
for analyzing VOC emissions from WPCs was assessed by measuring
VOC emissions from a WPC deck during a 41-day trial and comparing
VOC emission rates between seven different WPC decks.
Both hardwood and softwood distillates exerted positive effects on
the water resistance of the WPC; the addition of hardwood distillate
decreased the water absorption of the WPC by over 25% whereas at
least a 16% decrease was observed for the WPC with the softwood
distillate. Moreover, a 1 wt% addition of hardwood distillate into the
WPC led to a highly significant increase (11.5%, p < 0.01) in the tensile
modulus as well as achieving minor enhancements in some other
mechanical properties. Similarly, when 2 wt% of softwood was added
to the WPC, a highly significant increase in the tensile strength (5.0%,
p < 0.01) was observed. Even though the addition of the distillates
increased the total release of VOCs, the emission rates of harmful
compounds, such as benzene, remained low. Nonetheless, the results
from the VOC analyses indicated that some of the compounds
investigated in this thesis may be smelled from the WPCs because
their odor thresholds were exceeded.
Wood distillates displayed good potential as natural additives in
WPCs as they improved the mechanical properties and water
resistance. The results of this thesis provide a basis for the further
development of wood distillates as bio-based additives in WPCs.