Dissertations in Forestry and Natural Sciences

9 Summary and
conclusions
In the present thesis, the effects of thermally extracted wood
distillates on the properties of WPCs were successfully
determined. The effects of the distillates were investigated
through the mechanical tests, water absorption studies, and
VOC emissions analyses. The main conclusions with respect to
the aims are:
1. The impregnation of the WPC granules with the wood
distillate, originated from either hardwood or softwood, is
possible with the presented method. However, other
methods, such as impregnation of the agglomerate before
the granulation process, could well be more suitable. The
addition of distillates improved the processability of the
WPC granules.
2. PTR-TOF-MS can be applied to determine and compare the
release of VOCs from WPCs. The advantages of PTR-TOF-
MS include its rapid time response, high sensitivity, and
ease of use. In addition, there is no need for special sample
preparation. However, there are no regulatory limits for
VOC emissions measured with PTR-MS.
3. A small (1 wt%) addition of hardwood distillate
significantly increased the tensile modulus of the WPC.
Higher distillate contents (2–8 wt%) reduced the
mechanical properties of the WPC. In addition, the ability
of the material to absorb water was considerably decreased
in those containing the hardwood distillate. The VOC
emissions increased for the WPCs containing hardwood
distillate.
4. A minor (2 wt%) addition of softwood distillate
significantly increased the tensile strength of the WPC.
Dissertations in Forestry and Natural Sciences No 222 113