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The 23rd IPC
Effect of Heat Treatment on
Properties of Chinese White Poplar
Prof. Jianxiong LU
Dr. Yongjian CAO
Dr. Rongfeng HUANG
Research Institute of Wood Industry, CAF
Contents
Results and discussion3
Materials and Method2
Conclusion4
Introduction1
C R I W I , C A F
Introduction1
Part Ⅰ
Heat
treatment
C R I W I , C A F
What’s changed ?
C R I W I , C A F
Research Aim
Improving dimensional stability
Enhancing decay resistance
Darken color
Minimizing loss ratios of MOR or MOE
Establishing regression models
Extending application fields
C R I W I , C A F
Part Ⅱ
Materials and Method2
C R I W I , C A F
Materials
C R I W I , C A F
Facilities
C R I W I , C A F
Method & Parameters
Temp.（℃）
Time （h）
B1 =1 B2 =2 B3 =3 B4 =4 B5 =5
A1 ＝170 A1 B1 A1 B2 A1 B3 A1 B4 A1 B5
A2 ＝185 A2 B1 A2 B2 A2 B3 A2 B4 A2 B5
A3 ＝200 A3 B1 A3 B2 A3 B3 A3 B4 A3 B5
A4 ＝215 A4 B1 A4 B2 A4 B3 A4 B4 A4 B5
A5 ＝230 A5 B1 A5 B2 A5 B3 A5 B4 A5 B5
C R I W I , C A F
Part Ⅲ
Results and discussion3
3.1 Physical properties3.2 Chemistry analysis
3.3 Color analysis
3.4 Mechanical properties
C R I W I , C A F
Oven-dry density
0.38
0.39
0.40
0.41
0.42
0.43
0.44
0.45
155 170 185 200 215 230
密度
(g/c
m3)
Den
sity
温度(℃) Temp.
1h 2h 3h 4h 5h
0.38
0.39
0.40
0.41
0.42
0.43
0.44
0.45
0 1 2 3 4 5
密度
(g/cm3)
Density
时间(h) Time
170℃ 185℃ 200℃
215℃ 230℃
0
Range of loss ratios : 0.52% ～13.63%Effect of temp. > time
C R I W I , C A F
Weight loss ratio
0
3
6
9
12
15
170 185 200 215 230
失重率（%）
Weight loss ratio
温度（℃）Temp.
1h 2h 3h 4h 5h
0
3
6
9
12
15
1 2 3 4 5
失重
率（%）
Weight loss ratio
时间（h）Time
170℃ 185℃ 200℃215℃ 230℃
Range of loss ratios : 0.37% ～12.24%Effect of temp. > time
C R I W I , C A F
Air-dry shrinkage ASE
Range of ASE: 0.84% ～67.21%Effect of temp. > time
C R I W I , C A F
0
10
20
30
40
50
60
70
1 2 3 4 5
ASE
(%)
time (h)
170℃ 185℃ 200℃
215℃ 230℃
0
10
20
30
40
50
60
70
170 185 200 215 230
ASE
(%)
Temp. (℃)1h 2h 3h 4h 5h
Absolute dry shrinkage ASE
Range of ASE: 1.01% ～55.43%Effect of temp. > time
C R I W I , C A F
0
10
20
30
40
50
60
170 185 200 215 230
ASE
(%)
Temp. (℃)1h 2h 3h 4h 5h
0
10
20
30
40
50
60
1 2 3 4 5
ASE
(%)
Time (h)170℃ 185℃ 200℃215℃ 230℃
Air-dry swelling ASE
Range of ASE: 3.98% ～58.52%Effect of temp. > time
C R I W I , C A F
0
10
20
30
40
50
60
170 185 200 215 230
ASE
(%)
Temp. (℃)
1h 2h 3h 4h 5h
0
10
20
30
40
50
60
1 2 3 4 5
ASE
(%)
Time (h)170℃ 185℃ 200℃215℃ 230℃
Saturated swelling ASE
Range of ASE: 2.68% ～56.43%Effect of temp. > time
C R I W I , C A F
0
10
20
30
40
50
60
170 185 200 215 230
ASE
(%)
Temp. (℃)
1h 2h 3h 4h 5h
0
10
20
30
40
50
60
1 2 3 4 5
ASE
(%)
Time (h)170℃ 185℃ 200℃215℃ 230℃
Regression modelsloss ratio regression model R2 Adj. R2 Pr > F
absolute dry density ŷ＝0.139x1＋1.240x2－25.866 0.964 0.96 < .0001
weight loss ratio ŷ＝0.130x1＋1.144x2－24.526 0.942 0.937 < .0001
air dry shrinkage ratio ŷ＝0.999x1＋4.837x2－184.299 0.940 0.934 < .0001
absolute dry shrinkage ratio ŷ＝0.838x1＋3.924x2－153.255 0.960 0.956 < .0001
air dry swelling ratio ŷ＝0.596x1＋4.578x2－94.132 0.880 0.869 < .0001
water absorbed swelling ratio ŷ＝0.771x1＋3.419x2－134.318 0.973 0.971 < .0001
ŷ means loss ratio, x1 means temperature, x2 means time C R I W I , C A F
Discussion
1. Degradation of cellulose and hemicelluloses
2. Disappearance of inorganic and volatile materials
3. Change in hydrogen bond between surfaces of cellulose
C R I W I , C A F
Decay resistance
Ⅰ: strong decay resistance, 0 ～10% Ⅱ: decay resistance, 11 ～24% Ⅲ: little decay resistance, 25 ～44% Ⅳ: no decay resistance, >45%
C R I W I , C A F
Weight loss ratios
0
10
20
30
40
50
60
155 170 185 200 215 230
失重率(%)
Weig
htlo
ssra
tio
温度(℃) Temp.1h 2h 3h 4h 5h
0
10
20
30
40
50
60
0 1 2 3 4 5
失重率(%)
Weig
htlo
ssra
tio
时间(h) Time
170℃ 185℃ 200℃
215℃ 230℃
0
Range of loss ratios : 55.75% ～2.05%Effect of temp. > time
C R I W I , C A F
Data of weight loss ratio
Weight loss ratio (%)
Control 170℃ 185℃ 200℃ 215℃ 230℃
1h55.746 Ⅳ
44.690 Ⅳ
41.726 Ⅲ
38.374 Ⅲ
26.595 Ⅲ
18.648 Ⅱ
2h55.746 Ⅳ
43.423 Ⅲ
39.880 Ⅲ
34.280 Ⅲ
22.504 Ⅱ
8.086 Ⅰ
3h55.746 Ⅳ
42.123 Ⅲ
36.117 Ⅲ
27.829 Ⅲ
18.672 Ⅱ
7.317 Ⅰ
4h55.746 Ⅳ
39.014 Ⅲ
34.450 Ⅲ
25.294 Ⅲ
16.432 Ⅱ
3.157 Ⅰ
5h55.746 Ⅳ
37.612 Ⅲ
31.904 Ⅲ
21.474 Ⅱ
12.073 Ⅱ
2.052 Ⅰ
C R I W I , C A F
Discussion
Pyrogenation reactionLittle nutritional materials were not enough to fungiDecreased of cellulose and lignin in wood
896.
77
1057
.67
1109
.68
1159
.27
1227
.02
1268
.52
1319
.12
1372
.95
1424
.21
1459
.27
1510
.69
1604
.44
1657
.11
1736
.58
- 0 . 2
0 . 0
0 . 2
0 . 4
0 . 6
0 . 8
1 . 0
1 . 2
1 . 4
1 . 6
Abso
rban
ce
1000 1200 1400 1600 1800 Wavenumber s ( cm- 1)
C R I W I , C A F
Part Ⅲ
Results and discussion3
3.1 Physical properties
3.2 Chemistry analysis3.3 Color analysis
3.4 Mechanical properties
C R I W I , C A F
Holocellulose content
55
60
65
70
75
80
85
155 170 185 200 215 230
含量
(%)
Cont
ent
温度(℃) Temp.
1h 2h 3h 4h 5h
55
60
65
70
75
80
0 1 2 3 4 5
含量(%)
Content
时间(h) Time
170℃ 185℃ 200℃
215℃ 230℃
0
Range of loss ratios : 2.52% ～23.72%Effect of temp. > time
C R I W I , C A F
α- celluloses content
25
30
35
40
45
50
155 170 185 200 215 230
含量(%
)Co
nten
t
温度(℃) Temp.
1h 2h 3h 4h 5h
25
30
35
40
45
50
0 1 2 3 4 5
含量(%)
Content
时间(h) Time
170℃ 185℃ 200℃
215℃ 230℃
0
Range of loss ratios : 0.94% ～41.44%Effect of temp. > time
C R I W I , C A F
Lignin content
10
15
20
25
30
35
155 170 185 200 215 230
含量
(%)
Cont
ent
温度(℃) Temp.
1h 2h 3h 4h 5h
10
15
20
25
30
35
0 1 2 3 4 5
含量
(%0
Content
时间(h) Time
170℃ 185℃ 200℃
215℃ 230℃
0
Range of increase ratio : 9.06% ～123.64%Effect of temp. > time
C R I W I , C A F
Hemicellulose content
1h 2h 3h 4h 5h
control 32.12 32.12 32.12 32.12 32.12
170℃ 30.58 30.81 29.70 29.44 29.07
185℃ 29.75 28.63 26.32 24.64 27.69
200℃ 25.15 22.20 25.60 27.47 29.76
215℃ 24.44 24.33 24.77 28.87 31.91
230℃ 26.05 28.14 32.22 32.33 32.76
C R I W I , C A F
Question and key
Why?Should be decrease!
But increase? ? ?
C R I W I , C A F
Reaction mechanisms
(Source: VTT, Thermowood ® handbook)C R I W I , C A F
FTIR Spectra
896.
77
1057
.67
1109
.68
1159
.27
1227
.02
1268
.52
1319
.12
1372
.95
1424
.21
1459
.27
1510
.69
1604
.44
1657
.11
1736
.58
- 0 . 2
0 . 0
0 . 2
0 . 4
0 . 6
0 . 8
1 . 0
1 . 2
1 . 4
1 . 6
Abso
rban
ce
1000 1200 1400 1600 1800 Wavenumber s ( cm- 1)
C R I W I , C A F
Answer
So …
New materialswere produced in the thermal degradation process. However these new materials did not extracted thoroughly from three main chemical components.
C R I W I , C A F
Part Ⅲ
Results and discussion3
3.1 Physical properties
3.2 Chemistry analysis
3.3 Color analysis3.4 Mechanical properties
C R I W I , C A F
Color
CIE (1976) Color space
L* : white to dark
a* : red to green
b* : yellow to blue
△C* : saturation diff.
△E* : color diff.
△H* : hue diff.
C R I W I , C A F
△C*
-6
-4
-2
0
2
4
6
8
170 185 200 215 230
色差
值colo
rdi
ffer
ence
valu
e
温度(℃) Temp.
1h 2h 3h 4h 5h
-6
-4
-2
0
2
4
6
8
1 2 3 4 5
色差
值co
lor
differ
ence
value
时间 (h) Time
170℃ 185℃ 200℃
215℃ 230℃
Range of saturation diff. : 6.87 ～ － 5.14Effect of temp. > time
C R I W I , C A F
△E*
0
10
20
30
40
50
60
70
170 185 200 215 230
色差值
colordifference
value
温度(℃) Temp.
1h 2h 3h 4h 5h
0
10
20
30
40
50
60
70
1 2 3 4 5
色差值
colordifference
value
时间(h) Time170℃ 185℃ 200℃
215℃ 230℃
Range of color diff. : 13.98 ～ 62Effect of temp. > time
C R I W I , C A F
△H*
0
2
4
6
8
10
12
170 185 200 215 230
色差值
color
difference
value
温度(℃) Temp.
1h 2h 3h 4h 5h
0
2
4
6
8
10
12
1 2 3 4 5
色差值
colordi
fference
value
时间(h) Time
170℃ 185℃ 200℃
215℃ 230℃
Range of hue diff. : 3.63 ～ 10.46Effect of temp. > time
C R I W I , C A F
Regress models
change value regression model R2 Adj. R2 Pr > F
△C* ŷ＝21.972－0.064x1－ 2.110x2
0.819 0.802 < .0001
△E* ŷ＝0.226x1＋10.310x2－ 34.749 0.960 0.957 < .0001
△H* ŷ＝0.035x1＋1.092x2－ 3.128 0.942 0.937 < .0001
ŷ means change values, x1 means temperature, x2 means time
C R I W I , C A F
colors
More pictures …C R I W I , C A F
Discussion
C R I W I , C A F
Auxochrome :
Chromophoric groups :
Part Ⅲ
Results and discussion3
3.1 Physical properties
3.2 Chemistry analysis
3.3 Color analysis
3.4 Mechanical properties
C R I W I , C A F
Hardness
6
8
10
12
14
155 170 185 200 215 230
硬度
（N/
mm2）
Hard
ness
温度（℃） Temp.
1h 2h 3h 4h 5h
6
8
10
12
14
0 1 2 3 4 5
硬度
（N/
mm2 ）
Hard
ness
时间（h） Time
170℃ 185℃ 200℃215℃ 230℃
Range of loss ratios : － 15.82% ～ 22.09%Effect of temp & time
C R I W I , C A F
Bending strength
30
40
50
60
70
80
90
0 1 2 3 4 5
抗弯强度（MPa
）Bending
strength
时间（h） Time
170℃ 185℃ 200℃215℃ 230℃
30
40
50
60
70
80
90
155 170 185 200 215 230
抗弯强度（MPa）Be
nding strength
温度（℃） Temp.1h 2h 3h 4h 5h
0
Range of loss ratios : － 11.28% ～ 54.2%Effect of temp. > time
C R I W I , C A F
MOR
10
11
12
0 1 2 3 4 5
弹性
模量
（GPa）
MOE
时间（h） Time
170℃ 185℃ 200℃215℃ 230℃
10
11
12
155 170 185 200 215 230
弹性模量（GPa0 M
OE
温度（℃） Temp.
1h 2h 3h 4h 5h
0
Range of increase ratios : 2.73% ～ 15.8 %Effect of temp & time
C R I W I , C A F
Regression models
loss ratio ŷ( % ) regression model R2 Adj. R2 Pr > F
bending strength
ŷ＝0.961x1＋4.218x2－ 183.8316 0.953 0.948 < .0001
MOE ŷ＝0.089x1＋1.544x2－ 32.172 0.777 0.756 < .0001
ŷ means loss ratio, x1 means temperature, x2 means time
C R I W I , C A F
Discussion
Before 200 ℃& 2hrs,
New –OH were generated beteween fibers of wood;
thermal degradation seems to be ignored.
After 200 ℃& 2hrs,
Thermal degradation became harder and harder.
Fibre chains became shorter and shorter so that
mechanical strength was decreased step by step.
But, MOE was increased during the whole process.
C R I W I , C A F
Part Ⅳ
Conclusion4
C R I W I , C A F
Conclusion
Heat treatment can remarkably improve the dimensional
stability and decay resistance of wood.
Thermal degradation of chemical component is the
main reason for loss of mechanical strength of wood.
The temperature should be controlled at below 200 ℃
so that there is no loss or a minimum loss in the
mechanical strength of wood.
C R I W I , C A F
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