CHANGES IN THE CHEMICAL AND
MECHANICAL PROPERTIES OF ASH-TREE
WOOD AFTER HYDROTHERMAL
MODIFICATION
Grinins J., Biziks V. , Andersons B. , Andersone I., Puke M.
Latvian State Institute of Wood Chemistry,
Riga, Latvia
WSE 2011, 27. - 28. October, Oslo, Norway
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THE AIM
To investigate the thermal modification of ash-tree, to
ensure a longer lifetime and expand it’s applicability
for producing products with a higher added value.
WSE 2011, 27. - 28. October, Oslo, Norway
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THE TASK
To determine the effect of the hydrothermal treatment
on the chemical structure and mechanical properties
of ash-tree wood, to estimate optimal treatment
regimes (temperature, time).
WSE 2011, 27. ‐ 28. October, Oslo, Norway
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INTRODUCTION
The total stock of deciduous trees in the Republic of Latvia is ~250
million m3, from which approximately 2% is ash-tree. In the recent
years, studies have been initiated in Latvia on the use of soft
deciduous wood for producing products with a higher added value,
but practically, there are no studies on the thermal modification of
hard deciduous wood (ash-tree, oak). To forecast the properties of
the modified material as well as its stability in service conditions, it
is important to understand the processes occurring in wood as a
result of the thermal action.
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MATERIALS AND METHODS
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Materials and methods
Planks without visible defects
Physical properties
Hydrothermal treatment at 140, 160, 170 and 180°C for 1 and 3h
Analysis
Physical properties
Chemical
Mechanical
Geometrical
parameters
Extractives
Bending strength
Lignin
Hardness according
to Brinell
Mass
Cellulose
Holocellulose
Monosaccharides
WSE 2011, 27. - 28. October, Oslo, Norway
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RESULTS AND DISCUSSION
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Changes in the physical parameters of ash‐tree wood depending on the modification temperature
18
16
14
Mass loss
12
%
10
Density loss
W=12%
8
6
4
2
0
140/1
160/1
160/3
170/1
WSE 2011, 27. ‐ 28. October, Oslo, Norway
180/1
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Chemical composition of ash-tree wood
depending on the modification temperature
80
70
%
60
Extractives
50
Cellulose
40
Lignin
30
Hemicelluloses
20
Holocellulose
10
0
Un ‐
treated
140/1
160/1
160/3
170/1
WSE 2011, 27. ‐ 28. October, Oslo, Norway
180/1
9
60
Monosaccharides in the filtrate after the
isolation of Klason lignin
50
40
%
Xylose
30
Glucose
20
10
0
Untreated
140/1
160/1
160/3
170/1
WSE 2011, 27. ‐ 28. October, Oslo, Norway
180/1
10
4
Hydrothermally treated ash‐tree hardness according to the Brinell EN LVS 1534 test method
3,5
Hardness
3
Tangential
surface
2,5
2
Radial
surface
1,5
1
0,5
0
Untreated
140/1
160/1
160/3
170/1
WSE 2011, 27. ‐ 28. October, Oslo, Norway
180/1
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Bending strength of hydrothermally treated ashtree wood
140
120
MPa
100
80
60
40
20
0
Untreated
140/1
160/1
160/3
WSE 2011, 27. ‐ 28. October, Oslo, Norway
170/1
180/1
12
16
Modulus of elasticity of hydrothermally treated
ash-tree wood
14
12
GPa
10
8
6
4
2
0
Untreated
140/1
160/1
160/3
WSE 2011, 27. ‐ 28. October, Oslo, Norway
170/1
180/1
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CONCLUSIONS
With increasing hydrothermal treatment temperature for
ash-tree wood:
1. Density decreases and mass losses grow;
2. Relative amounts of extractives, cellulose and lignin
grow. No linear relationship is observed for the
changes in the holocellulose amounts. The calculation
testifies that the amount of hemicelluloses decreases.
3. In the filtrate, after the isolation of Klason lignin, the
relative glucose amount increases, and the relative
amount of xylose decreases.
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4. Surface hardness, both in tangential and radial
direction, decreases. Tangential surface hardness is
higher by 5-20% than that for the radial surface.
5. Modulus of elasticity grows at the first treatment
regimes (140°C and 160°C/1h), then decreases.
Bending strength decreases.
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ACKNOWLEDGEMENT
The authors gratefully acknowledge the financial
support by the Latvian Scientific Council grant No.
1600 and State Research Program “NatRes”.
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Thank you for your attention!
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