Physical-Mechanical Properties of Wood
Industrial Heat treated with Different
Methods
Peter Niemz1) ,Tamás Hofmann2), Melanie Wetzig1) ,Tamás Rétfalvi2)
1)ETH Zurich , Institute for Building Materials; 2) University of West Hungary,
Sopron
[email protected]
1 Introduction
ƒ First publications by Stamm 1937 (USA)
ƒ 1960-1980 many publications
a) Kollmann and Schneider 1963:
Treatment in oxygen atmosphere
b) Burmester 1973, 1975:
FWD-method
c) Giebler 1981:
Treatment in autoclave with nitrogen atmosphere (since 2001
industrial application in Switzerland, Balz Holz AG)
ƒ Since 1990: industrial application: Netherlands, France,
Germany, Switzerland, Austria, Finland
ƒ Production: ca. 200.000m3 / year (2010)
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2 Aims of thermal modification
Primary ideas:
ƒ Increasing durability
ƒ Increasing dimensional stability
Derived ideas / partial main focus of selling:
ƒ Colour changes
Substitute for tropical wood (hardwood)
ƒ Substitute for naturally aged wood (softwood)
ƒ
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3 Application fields of heat-treated wood
Outdoor applications:
ƒ Claddings, noise barriers, terrace floors, windows/doors
¾
Due to increased durability and dimensional stability
Indoor applications:
ƒ Parquet floors, furniture, substitute for naturally aged and
tropical wood
¾
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Due to colour changes and increased dimensional stability
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Using of thermally treated spruce
House produced from naturally
aged wood Chaletbau Matti/CH
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thermally treated wood
Balz Holz/CH
Comparison of different methods to produce heat-treated wood
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Using of thermally modified hardwood
(for furniture)
Thermally treated beech (Airport Zurich)
Furniture:. Bikos/Germany)
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Using of thermally treated wood for
gladdings
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4 Industrial thermal modification methods
ƒ Vacuum-press-dewatering-method (Vacu3)
Treatment temperature devolves the wood samples using heating
plates, (Timura, D), vacuum+ pressure (hot plates), T up to 240oC,
ƒ Pressure 80mbar
ƒ
ƒ Autoclave with steam
Balz Holz AG
atmosphere (Corbat, CH),T 170oC
Pressure 3bar
Autoclave with inert gas
atmosphere (nitrogen) (Balz, CH)
pressure 7bar, T up to 170oC
Autoclave: 6m x 1,05m x 1,30m
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Vacuum-press-dewatering-method
(Vacu3), Opel Therm (Timura/Germany)
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5 Properties of heat-treated wood
5.1 Physical properties
ƒ Colour changes
untreated
treated in autoclave (180°C)
treated by Vacu3 (195°C)
¾ Degree of colour change depends on the used
modification process as well as the intensity
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5 Properties of heat-treated wood
5.1 Physical properties
ƒ Colour changes
heat-treated I
heat-treated II
BÄCHLE, SCHMUTZ (2006)
untreated
Treatment intensity rises from heat-treated I to heat-treated II
Counterbalanced differences between coloured and
uncoloured heartwood
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5 Properties of heat-treated wood
5.1 Physical properties
ƒ None UV-stability
Colour changes after 6 month natural weathering
beech
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ash
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5 Properties of heat-treated wood
5.1 Physical properties
ƒ Equilibrium moisture content (EMC)*
*in %, at 20°C and 65% relative humidity
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ƒSorption velocity perpendicular to the grain Sp, m
and water diffusion resistance factor µm to the
grain (mean values)
,
0.5
beech
DryCup
ash
beech
WetCup
ash
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untreated
method A
method B
untreated
method A
method B
[m/s ]
−3.580·10−7
−2.066·10−7
−2.052·10−7
−3.083·10−7
−1.898·10−7
−1.747·10−7
[-]
153.67
516.20
474.98
201.93
437.40
441.88
untreated
method A
method B
untreated
method A
method B
9.108·10−7
3.418·10−7
5.187·10−7
8.167·10−7
3.061·10−7
3.719·10−7
22.95
154.67
79.58
35.57
164.02
175.78
Comparison of different methods to produce heat-treated wood
5 Properties of heat-treated wood
5.1 Physical properties
ƒ Swelling
beech
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ash
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5 Properties of heat-treated wood
5.1 Physical properties
ƒ Density
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5 Properties of heat-treated wood
5.1 Physical properties
ƒ Modulus of elasticity (MOE)
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5 Properties of heat-treated wood
5.1 Physical properties
ƒ Bending strength
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5 Properties of heat-treated wood
5.1 Physical properties
ƒ Brinell hardness
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5 Properties of heat-treated wood
5.1 Physical properties
ƒ Thermal conductivity λ10 [W/(m*K)]
Ash
beech
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Comparison of different methods to produce heat-treated wood
Color
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Comparison of different methods to produce heat-treated wood
5 Properties of heat-treated wood
5.2 Structural properties
ƒ Cracking fissuration into the cell walls
ash untreated
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ash heat-treated by variant B
Comparison of different methods to produce heat-treated wood
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5 Properties of heat-treated wood
5.3 Chemical properties
ƒ Total phenol content*
HOFMANN, T. (2010)
*in mmol quercetin/100g dry wood
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5 Properties of heat-treated wood
5.3 Chemical properties
ƒ Soluble carbohydrate content*, method A
HOFMANN, T. (2010)
*in mg glucose/g dry wood
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5 Properties of heat-treated wood
5.3 Chemical properties
ROFFAEL, E.; KRAFT, R. (2010); ROFFAEL, E.; KRAFT, R., NIEMZ, P. (2008)
*in mg /100g dry wood; reviewed by the flask method (40°C, 24h)
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5.3 Chemical properties (Ash, treatment method A)
ƒ Waste water - Main component analysis with GC-MS
Retention
Compound name
Time
3.241
2,3-butanedione
A
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Area*
3473438
4.054
Acetic acid
204269540
4.135
4.453
4.643
3-methyl-butanal
1-hydroxy- 2-propanone
1-methoxy-2-propanone
83427
846463
183601
4.787
2,3-pentanedione
375347
5.014
Propionic acid
5.202
3-hydroxy-2-butanone
284028
6.235
1-hydroxy-2-butanone
583496
7.318
Furfural
8.633
8.700
8.922
1-(2-furanyl)-ethanone
Butyrolactone
2,5-hexanedione
9.117
5-methyl-2(5H)-furanone
9.425
5-methyl-furfural
2376812
50261034
370478
293136
63978
91965
5489972
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5.3 Chemical properties (Ash, treatment method A)
ƒ Waste water - Micro component analysis with GC-MS
B
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10.801
10.880
11.128
11.524
12.432
12.790
14.091
14.676
14.900
15.497
15.856
16.124
17.013
17.596
17.705
18.173
19.539
4-oxo-pentanoic acid
2-furancarboxylic acid
2-methoxy-phenol
Maltol
1,2-benzenediol
5-hydroxymethyl-furfural
2,6-dimethoxy- phenol
Vanillin
4-hydroxy-benzeneethanol
Acetovanillone
1-(4-hydroxy-3-methoxyphenyl)-2-propanone
Vanillic acid
4-hydroxy-3,5-dimethoxy-benzaldehyde
1-(4-hydroxy-3,5-dimethoxyphenyl)- ethanone
4-hydroxy-2-methoxycinnamaldehyde
4-hydroxy-3,5-dimethoxybenzoic acid
3,5-dimethoxy-4-hydroxycinnamalde
Comparison of different methods to produce heat-treated wood
34355578
8887595
2852988
9426876
7901331
56289943
11416106
25759304
22705462
4376276
6594803
10740874
28988740
2846732
7848213
2187070
3972230
27
5.3 Chemical properties (treatment method A)
ƒ Waste water analysis with GC-MS
1: 1-hydroxy-2-propanone,
2: propionic acid,
3: 1-hydroxyde-2-butanone,
4: 1-(2-furanyl)-ethanone,
5: 4-oxo-pentanoic acid,
6: maltol,
7: 5-hydroxymethyl-furfural,
8: 4-hydroxy-4-trimethyl-cyclohexanemethanol,
9: 2,6-dimethoxy-phenol,
10: vanillin,
11: 4-hydroxy-benzeneethanol,
12: acetovanillone,
13: vanillic acid,
14: unknown component,
15: 4-hydroxy-3,5-dimethoxy-benzaldehyde,
16: 4-hydroxy-2-methoxycinnamaldehyde,
Waste water from the treatment of Ash,
Ash Spruce
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17: 4-hydroxy-3,5-dimethoxybenzoic acid,
18: 3,5-dimethoxy-4-hydroxycinnamaldehyde
5 Properties of heat-treated wood
5.4 Workability
ƒCharacteristic offensive smell (depending from the
method)
ƒDecreased water absorption (perpendicular to the grain
direction)
ƒPartially higher pressing time by gluing (lower
equilibrium moisture content and pH-value)
ƒIncreased internal stresses when gluing treated and
untreated wood together
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6 Conclusion
ƒColour changes depending on the process used and on
the intensity of the treatment
ƒPhysical-technological properties generally decreased
with increasing heat-treatment intensity
ƒChanged chemical properties in consequence of heattreatment
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Thank you for your attention
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