Dissertations in Forestry and Natural Sciences

8 Discussion
In the present thesis, the effects of hardwood and softwood
distillates on the characteristics of commercial WPCs were
studied. The first objective of this thesis was to assess the
suitability of the impregnation method used to incorporate the
distillates into the WPC granules. The suitability of wood
distillates as additives in WPCs was determined by conducting
mechanical tests, water absorption studies, and via a
characterization of VOC emission rates. In addition, the
applicability of PTR-TOF-MS for determining the VOC
emissions from WPCs was assessed.
8.1 IMPREGNATION OF WPC GRANULES WITH WOOD
DISTILLATES
The impregnation of the WPC granules with the distillates was
successfully performed for the LG granules but not for the UFs.
Commercially available granules were used in this thesis
because the impregnation of the WPC granules with the
distillates was both straightforward and quick and there were
no suitable facilities with which to produce WPC granules from
raw materials. Commercialized WPC granules contain multiple
additives, and theoretically, these could have interfered with
the modifications investigated here. Nonetheless, the present
results clearly demonstrated that wood distillates can be added
to certain types of WPC granules and this can improve their
processability during injection molding.
In future studies, the incorporation of distillates into WPCs
could be carried out at an earlier stage of the WPC production.
The impregnation of the agglomerate or wood particles with the
distillates could eliminate at least some of the limitations
associated with the impregnation of WPC granules. For
Dissertations in Forestry and Natural Sciences No 222 97