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

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Introduction1

Part Ⅰ

Heat

treatment

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What’s changed ?

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Research Aim

Improving dimensional stability

Enhancing decay resistance

Darken color

Minimizing loss ratios of MOR or MOE

Establishing regression models

Extending application fields

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Part Ⅱ

Materials and Method2

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Materials

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Facilities

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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

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Part Ⅲ

Results and discussion3

3.1 Physical properties3.2 Chemistry analysis

3.3 Color analysis

3.4 Mechanical properties

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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

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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

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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

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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

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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