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THE EFFECT OF THERMAL TREATMENT USING VEGETABLE OILS ON PHYSICAL AND MECHANICAL PROPERTIES OF POPLAR AND ROBINIA WOOD
Robert NEMETH
Dr. - Institute of Wood Sciences, University of
West Hungary
Address: Bajcsy-Zs. U. 4, H-9400 Sopron, Hungary
E-mail: nemethr@fmk.nyme.hu
Miklos BAK
Dr. - Institute of Wood Sciences, University of
West Hungary
Address: Bajcsy-Zs. U. 4, H-9400 Sopron, Hungary
Laszlo TOLVAJ
Prof.Dr - Institute of Wood Sciences, University
of West Hungary
Address: Bajcsy-Zs. U. 4, H-9400 Sopron, Hungary
Sandor MOLNAR
Prof.Dr - Institute of Wood Sciences, University
of West Hungary
Address: Bajcsy-Zs. U. 4, H-9400 Sopron, Hungary
Abstract: Pannonia
Poplar (Populus × euramericana Pannonia)
and Robinia (Robinia pseudoacacia L.) were treated
at 160°C and 200°C in different vegetable
oils, in absence of Oxygen, using laboratory equipment.
Three different vegetable oils were used, namely
sunflower oil, linseed oil and rapeseed oil. Three
different durations were chosen for the thermal
treatment: 2h, 4h and 6h. The aim of the research
work was to prove, in what extent the treatments
influence some important characteristics of the
wood. The investigated properties were: MOR, impact
bending, compression strength, ASE and colour.
Untreated samples from the same wood material
served as control. The treatments decreased the
impact bending in case of Robinia and poplar as
well. Longer duration of the treatment delivered
proportionally lower values in impact bending.
The same could be observed regarding the MOR values
for Robinia, whereas in case of Poplar the more
intensive treatments (longer duration and higher
temperature) caused a significant increase in
MOR. Regarding the compression strength values
the treatments resulted in higher strength values
by Poplar, whereas in case of Robinia a clear
increase could be observed at 160°C, and a
significant decrease at 200°C. As a consequence
of the treatments the dimension stability could
be enhanced for both wood species, so the ASE
values increased with increasing duration and
temperature. The treatments caused significant
darkening for both wood species by all temperatures.
The colour coordinates L* and a* (lightness and
red hue) shifted to the same direction for both
species. The value b* (yellow hue) increased for
Poplar, whereas a decreasing was observed for
Robinia. Comparing the oils used for this research
work, no significant differences in effectiveness
could be proved for the investigated properties.
An important observation for the practical use
was done, as in Robinia wood numerous cracks could
be observed in case of wet samples, while practically
no damages (cracks, collapses) were observed in
Poplar wood using wet samples. The treatments
on laboratory scale enhanced the dimensional stability
by acceptable decrease in mechanical stability
for Robinia and in an increase for Poplar. The
results encourage the authors to perform further
investigations towards development of technologies
for industrial application.
Key words: wood modification, Poplar,
Robinia, vegetable oil, colour, ASE, OHT.
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SAILER, M.; RAPP, A.O.; LEITHOFFH, PEEK, R.D.
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STAMM, A.J; BURR, H.K; KLINE, A.A (1946). Heat
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