Green composite

8/9/2019 Green composite

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Development of green composite consists of woodchips, bamboo fibers

and biodegradable adhesive

Hiroyuki Kinoshita a,*, Koichi Kaizu b, Miki Fukuda a, Hitoo Tokunaga c, Keisuke Koga d, Kiyohiko Ikeda a

a University of Miyazaki, Gakuen-Kibanadai-Nishi, Miyazaki City 889-2192, Japanb University of Hyogo, Shosha, Himeji City 671-2280, Japanc Ube National College of Technology, Tokiwadai, Ube City 755-855, Japand Matsushita Ecology Systems Co., Ltd., Japan

a r t i c l e i n f o

Article history:

Received 9 October 2008

Received in revised form 12 January 2009

Accepted 17 January 2009

Available online 18 April 2009

Keywords:

A. Wood

A. Fibers

B. Adhesion

B. Mechanical properties

a b s t r a c t

From the viewpoint of the effective utilization of waste wood, the green composite which is produced by

solidifying woodchips has been developed [Miki M, Takakura N, Kanayama K, Yamaguchi K, Iizuka T.

Effects of forming conditions on compaction characteristics of wood powders. Trans Jpn Soc Mech Eng

C 2003;69(678):502–8 [in Japanese]; Miki M, Takakura N, Kanayama K, Yamaguchi K, Iizuka T. Effects

of forming conditions on flow characteristics of wood powders. Trans Jpn Soc Mech Eng C

2003;69(679):766–72 [in Japanese]; Miki M, Takakura N, Iizuka T, Yamaguchi K, Kanayama K. Possibility

and problems in injection moulding of wood powders. Trans Jpn Soc Mech Eng C 2004;70(698):2966–72

[in Japanese]]. Since the composite was solidified by the compressive load without the binder, it did not

have the high strength and was very brittle, and it had no water resistance [Kinoshita H, Kaizu K, Koga K,

Tokunaga H, Ikeda K. In: Proceeding of the Japan Society of Mechanical Engineers M& M2007; 2007. CD

[in Japanese]]. In this study, to improve these defects, it was proposed that a biodegradable resin as an

adhesive andbamboo fibers as reinforced fibers were applied to thewoodchip composite. By using wood-

chips with two kinds of the particle size, bamboo fibers with three kinds of the length and the biodegrad-

able adhesive, several kinds of specimens changed mixing ratio of those materials were produced by

compression molding at the appropriate temperature. By examining the bending strength and impact

strength of the composites, it was found that the high bending strength was obtained in the case where

woodchips with the small particle size and long bamboo fibers were used, and the high impact strength

was obtained in the case where woodchips with the large particle size andlong bamboofibers were used.

2009 Elsevier Ltd. All rights reserved.

1. Introduction

Green composites are expected to be widely used in place of

polymer composites made from fossil oil and to contribute to the

maintenance of a sustainable productive society. Many green com-

posites which consist of natural fibers as reinforcements and a bio-

degradable resin as a matrix material are proposed. Natural fiberssuch as bamboo [5], hemp [6] and kenaf [7] are light, strong,

renewable and inexpensive. Many attempts which use the natural

fibers practically have been performed. For example, in the case of

automobile components, the natural fibers have been used instead

of glass fibers [8]. The biodegradable resin is resolved into water

and carbon dioxide by the microorganism. The green composites

are environmental friendly materials.

Recently, the composite produced by solidifying woodchips has

been developed for effective utilization of waste wood [1–3]. The

composite does not damage the environment because it is com-

posed of only the woodchips which is a natural resource. The waste

woodchips generated by lumbering of the wood can be utilized

effectively. The products with complicated shapes can be formed

by compression molding of woodchips at the appropriate temper-

ature. However, the composite which is produced by solidifying

only the woodchips without the binder does not have the highstrength, and it is brittle partially and its water resistance is bad.

Therefore, to improve these defects, we used the biodegradable re-

sin as an adhesive [4]. Moreover, to obtain the higher strength, we

used the bamboo fibers as a reinforced fiber. The bamboo fibers

have the high strength in comparison with other natural fibers.

The supply of the bamboo fibers has been stabilized because the

growth rate of the bamboo is very rapid. However, recently, the

bamboo disrupts forest and the utilization of the bamboo also

decreases due to the insufficient maintenance of the bamboo thick-

et. Excellent mechanical properties of bamboos should be effec-

tively utilized from the viewpoint of the effective utilization of

natural resources. All of woodchips, bamboo fibers and the biode-

1359-8368/$ - see front matter 2009 Elsevier Ltd. All rights reserved.doi:10.1016/j.compositesb.2009.04.004

* Corresponding author. Tel.: +81 985 58 7290; fax: +81 985 58 2876.

E-mail address: [email protected] (H. Kinoshita).

Composites: Part B 40 (2009) 607–612

Contents lists available at ScienceDirect

Composites: Part B

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c o m p o s i t e s b

mailto:[email protected]://www.sciencedirect.com/science/journal/13598368http://www.elsevier.com/locate/compositesbhttp://www.elsevier.com/locate/compositesbhttp://www.sciencedirect.com/science/journal/13598368mailto:[email protected]


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gradable adhesive which we use as ingredients for the composite

do not give the damage to the environment. Therefore, our pro-

posed green composite are also friendly to the environment. It will

be a great help in saving resources by using the waste woodchips

and bamboo fibers.

In this study, by using woodchips with two kinds of the particle

size, bamboo fibers with three kinds of the length and the biode-

gradable adhesive, several kinds of specimens changed mixing ra-

tio of those materials were produced by compression molding at

the appropriate temperature. With regard to our proposed green

composite, a small quantity of the biodegradable resin is used

and the matrix consists of the woodchips impregnated slightly

with the biodegradable resin. The matrix of the composite is not

made by burying woodchips in the resin. The biodegradable resin

is used to coat woodchips for improvement of the water resistance

and is also used to strengthen the adhesion of woodchips for

improvement of the strength. In order to evaluate mechanical

properties of the composite, we focus on the effects of the biode-

gradable adhesive and bamboo fibers on the bending strength

and impact strength. Therefore, by the four-points bending test

and Charpy impact test, the bending strength and impact strength

of the specimens made under some conditions were examined. In

addition, by Charpy impact tests using the specimens absorbed

water, the effect of its water resistance on the impact strength

was examined. From the experimental results, the effects of the

biodegradable adhesive and bamboo fibers on the bending

strength and impact strength of the proposed green composite

were clarified.

2. Experiments

2.1. Specimens

Woodchips with two kinds of the particle size and three kinds

of bamboo fibers, and the biodegradable adhesive were used as

ingredients for specimens. Fig. 1 shows samples of woodchips

and bamboo fibers used as ingredients for specimens. We used

woodchips of the Japanese cedar. The woodchips have the particle

size of 1 mm or less and 200lm or less, respectively. The bamboo

fibers [9] have 1 mm in diameter and the length of 10 mm, 20 mm

and 30 mm, respectively. The mechanical properties of the wood

and bamboo fibers used as ingredients for specimens are listed in

Table 1. As the biodegradable adhesive, Landy CP-100 [10,11]

was used. The biodegradable adhesive is the aqueous dispersion

of starchy fatty acid ester (CORNPOL resin [12]) made from the

cornstarch. Landy CP-100 is accessioned as ‘‘Green Plastics” by Ja-

pan bioplastics association [13]. The main mechanical properties of

Landy CP-100 are listed in Table 2. The adhesive has the property

that the adhesive strength is maximum between 120 C and

140 C.

We made eight types of specimens using woodchips with twokinds of the particle size for the bending test and Charpy impact

test, respectively, as listed in Table 3. Fig. 2 shows the forming

process of the specimens. The specimens for bending tests were

made by mixing woodchips and bamboo fibers with weight of

5 g in total, and the biodegradable adhesive with the weight of

4 g. The specimens have the length of 60 mm, the width of

18 mm and the depth of 5.6–8.5 mm in a rectangular cross section.

The specimens for Charpy impact tests were made by mixing

woodchips and bamboo fibers with the weight of 4 g in total, andthe biodegradable adhesive with the weight of 3.2 g. The speci-

Bamboo fibersWoodchips Woodchips(Length: 20mm)(Size: 200 m)(Size:1mm)

Fig. 1. Materials used as specimens.

Table 1

Mechanical properties of wood and bamboo fiber used as ingredients for specimen.

Tensile strength of wood (Japanese cedar) 55 MPa

Compressive strength of wood 28 MPa

Bending strength of wood 90 MPa

Impact energy of wood 3.6 J/cm2

Tensile strength of bamboo fiber 290 MPa

Table 2

Mechanical properties of Landy CP-100.

Properties Landy CP-100

Density (g/cm3) 1.13

Grass transition temperature (C) 60

Softening temperature (C) 39

Young’s Modulus (MPa) 540

Tensile strength (MPa) 25

Total elongation (%) 110

Absorption (%) 5.0

Adhesive strength (MPa)

Temperature of adhesive

80 C 1.0

100 C 1.5

120 C 4.0

140 C 3.5

160 C 2.0

Table 3

Types of specimens.

No. Types of specimens

1 Woodchips 100% without adhesive

2 Woodchips 100% with adhesive

3 Length of bamboo fiber: 10mm (with adhesive) Content: 10%

4 Content: 20%


6 Content: 20%


8 Content: 20%

Compression

Woodchips Bamboofibers

Biodegradable

adhesive

Fig. 2. Forming of the specimen.

608 H. Kinoshita et al. / Composites: Part B 40 (2009) 607–612


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mens have the length of 55mm, the width of10 mm and the depth

of 8.0–10.0 mm, and does not have notch. The specimens for bend-

ing tests were made by pressing at a pressure of 15 MPa using the

universal testing machine and holding for 3 h at the temperature of

130 C. Similarly, the specimens for Charpy impact tests were

made by pressing at a pressure of 30 MPa and holding for 3 h at

the temperature of 130 C.

2.2. Experimental methods

Fig. 3 shows a schematic illustration of the four-points bending

test. The tests were carried out using the universal testing machine

(Simadzu AG-500A) at the crosshead speed of 0.5 mm/s. The max-

imum bending stress is given by the following equation:

r f ¼ 3P ðL aÞ

2bh2

ð1Þ

where P is the maximum load, L is the distance between lower sup-

porting points, a is the distance between upper loading points, b

and h are the width and the depth in a rectangular cross section

of the specimen, respectively. Charpy impact tests were carried

out in conformity to the Japanese Industrial Standards (JISZ2202).

3. Results and discussions

3.1. Microstructures of specimens

Fig. 4 shows examples of specimens with adhesive made for

bending tests. The surfaces of specimens were polished and photo-

graphed. From Fig. 4(B), we can show some bamboo fibers in the

matrix of the composite.

Fig. 5 shows microstructures of specimens observed by the sub-

stance microscope.

From Fig. 5(A), it is found that the specimen with the wood-

chips size of 1 mm or less has more voids between the particles

than the specimen with the woodchips size of 200 lm or less.

Also, from the comparison of the specimen of only the wood-

chips without the biodegradable adhesive in Fig. 5(A) and thespecimen with the biodegradable adhesive in Fig. 5(B), it is

found that the number of voids between the particles consider-

ably decreases in the case where the biodegradable adhesive is

added to the woodchips. It seems to be a cause that the adhe-

sion between particles is intensified by adding the adhesive.

From Fig. 5(C), it is also found that the bamboo fibers have been

buried in the particles of the woodchips. The fibers bend and a

part of fibers overlap each other.

3.2. Bending strength

Fig. 6 shows comparison of the bending strengths obtained by

four-points bending tests. The symbols of and j shown inFig. 6 express the average of five samples of the bending strengths

and the error bars which show the standard deviation. First, we

examine the influences of the biodegradable adhesive on the bend-

(A) Specimen of woodchips 100% with

adhesive (Woodchips size: 1mm or

less)

(B) Specimen with Bamboo fibers:

(Fiber length: 10mm, content: 20%,

woodchips size: 1mm or less)

20mm

Fig. 4. Examples of specimens with adhesive.

Fig. 5. Microstructures of specimens observed by substance microscope.

10

5 . 6

8 . 5

26

Specimen

Fig. 3. Bending test.

H. Kinoshita et al./ Composites: Part B 40 (2009) 607–612 609


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ing strength. From the results of comparing the No. 1 specimen

(the specimen is composed of only the woodchips without the bio-degradable adhesive) with the No. 2 specimen (the specimen is

composed of the woodchips with the biodegradable adhesive), it

is found that the bending strength remarkably increases by addi-

tion of the biodegradable adhesive.

Second, we examine the influences of the bamboo fibers on the

bending strength. The bending strengths of the No. 3–8 specimens

composed of the woodchips with the particle size of 200lm orless

and the bamboo fibers are higher than that of the No. 2 specimen

composed of only the woodchips. And the bending strength in-

creases as the fibers becomelonger and the content of the fibers in-

creases. On the other hand, the bending strengths of the specimens

composed of the woodchips with the particle size of 1 mm or less

and the bamboo fibers increase except for the No. 3 specimen with

the fiber length of 10 mm and content of 10%. Fromthose results, itis found that the bending strength increases remarkably by mixing

long bamboo fibers with woodchips.

Third, we examine the influences of the particle size of wood-

chips on the bending strength. For the No. 1 specimens composed

of only the woodchips without the biodegradable adhesive, their

bending strengths are low in both particle sizes and the effect of

the particle size is not found in those results. On the other hand,

with regard to specimens with the biodegradable adhesive, the

bending strengths of the specimens composed of the woodchips

with the particle size of 200 lm or less are higher than those of

the specimens composed of the woodchips with the particle size

of 1 mm or less. Particularly, the bending strengths of the speci-

mens composed of the woodchips with the particle size of

200lm or less and bamboo fibers with the length of over 20 mmare very high. From those results, in the case of using the biode-

gradable adhesive, it is found that the bending strength is high

when woodchips with the small particle size are used. It seems

to be a cause that the voids in the specimen decrease since the par-

ticle size is small, and the adhesion of woodchips becomes firm.

From the results, it is clarified that the bending strength of the

specimen composed of woodchips with the small particle size, long

bamboo fibers and the biodegradable adhesive is very high.

3.3. Impact strength

Fig. 7 shows comparison of impact energy by Charpy impact

test. The symbols of and j shown in Fig. 7 express the average

of five samples of impact energy and the error bars which showthe standard deviation. From the results for the No. 1 specimen

composed of only the woodchips without the biodegradable adhe-

sive and the No. 2 specimen with the biodegradable adhesive, theimpact strength increases slightly when only the biodegradable

adhesive is added to the woodchips. Namely, it is found that the

biodegradable adhesive is not effective for the improvement on

the impact strength. When both the bamboo fibers and the biode-

gradable adhesive are mixed with the woodchips, the impact

strength is higher than that of the specimen composed of only

the woodchips. As well as the case of the bending strength, the

impact strength is improved as the length of the bamboo fiber

becomes longer and the content of the bamboo fiber increases. Par-

ticularly, the impact strengths of the No. 6 and No. 8 specimens are

very high. In the case of those specimens, the bamboo fibers with

the length of 20 mm or 30 mm are mixed with content of 20%.

From those results, it is found that bamboo fibers have a good ef-

fect on the improvement of the impact strength, and long bamboofibers increase remarkably the impact strength. Fig. 8 shows exam-

ples of fractured specimens after Charpy impact tests. They are No.

2 and No. 8 specimens with the particle size of 1 mm or less,

respectively. It seems to be a cause of the improvement for the im-

pact strength that the crack extension resistance increases by

bridging of bamboo fibers as shown in Fig. 8. In regard to the influ-

ences of the particle size of woodchips on the impact strength, the

impact strengths in the cases where woodchips with the particle

size of 1 mm or less were used are higher than those in the cases

where woodchips with the particle size of 200 lm or less were

used. From experimental results of the bending strength in Fig. 6

and the impact strength in Fig. 7, it is found that the specimen with

the small particle size of the woodchips has the high bending

strength and the specimen with large particle size of the wood-

chips has the high impact strength. When the small particles for

woodchips are used, the adhered interfaces between the bamboo

fibers and the woodchip particles increase. When the large parti-

cles for woodchips are used, the adhered interfaces between the

0

5

10

15

20

25

B e n d i n g s t r e

n g t h M P a

Specimen No.

1 2 3 4 5 6 7 8

Woodchip size: 1mm or less

Woodchip size: 200 m or less

Fig. 6. Comparison of bending strength.

Specimen No.

1 2 3 4 5 6 7 8

Woodchip size: 1mm or less

Woodchip size: 200 m or less

I m p a c t e n e r g y J / c m

2

0.0

1.0

2.0

3.0

4.0

5.0

Fig. 7. Comparison of impact energy by Charpy impact tests.

Fig. 8. Fracture of specimens after Charpy impact tests.



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bamboo fibers and the woodchip particles decrease, but the bam-

boo fibers are bent by the large particles from Fig. 5(C). In the case

of the bending test at the quasi-static load, the composite is frac-

tured by the crack extension in the woodchip matrix as the tensile

stress increases. Therefore, it is considered that the effect of the

adhesive strength between the woodchip particles on the bending

strength is bigger than the effect of the bamboo fibers. On the other

hand, in the case of the impact test, the composite is also fracturedby the crack extension in the woodchip matrix as the tensile stress

increases, but the bamboo fibers show the effect of the reinforce-

ment after fracture of the matrix. The resistance for pulling out

the bamboo fibers in the composites with the large woodchip par-

ticles is larger than that of the composites with the small woodchip

particles because the bamboo fibers is bonded to the woodchip

particles in the condition that the fibers are complicatedly bent.

Therefore, the reinforcement by bamboo fibers remarkably influ-

ences the impact strength.

3.4. Water resistance

To examine the water resistance for produced specimens,

Charpy impact tests using the specimens absorbed water were car-ried out. The impact tests were carried out using the No. 1–No. 8

specimens composed of woodchips with the particle size of

1 mm or less as shown in Table 3. Also, the specimens with the

water absorption of about 50% which were obtained by soaking

them in the water and the specimens dried to about 0% after they

were soaked in the water to the water absorption of about 50%

were used for the tests. Fig. 9(A) shows comparison of impact en-

ergy of the specimens with the water absorption of about 50%.

Fig. 9(B) shows comparison of impact energy of the specimens with

the water absorption of about 0%. The symbol of shown in

Fig. 9(A) and (B) expresses the average of samples and the error

bars which show the standard deviation. From Fig. 9(A), it is found

that the No. 1 specimen without the biodegradable adhesive which

absorbed water dose not have the impact strength at all. On the

other hand, it is also found that No. 2–No. 8 specimens that the bio-

degradable adhesive is added keep having the strength, respec-

tively, though the impact strengths become lower by absorbing

water. Particularly, the specimens with long bamboo fibers have

the high impact strengths. From Fig. 9(B), it is found that the im-

pact strengths of No. 2–No. 8 specimens recover considerably by

drying after soaking. The water resistance is improved by the bio-

degradable adhesive and the long bamboo fiber. They are effective

in the case where the woodchip matrix is deteriorated by the

water.

4. Conclusions

To improve the strength and water resistance for the composite

made of only the woodchips, the composite composed of wood-

chips as the matrix material, bamboo fibers as the reinforced fiber

and the biodegradable resin as the adhesive was proposed, and its

strength and water resistance were examined. The results obtained

from the experiments are as follows:

(1) The bending strength increases by adding the biodegradable

adhesive to woodchips, and it increases remarkably by add-

ing long bamboo fibers in addition.(2) The impact strength increases slightly when only the biode-

gradable adhesive is added to the woodchips, and the impact

strength increases remarkably and the water resistance is

also improved when long bamboo fibers are added in

addition.

(3) The bending strength is high when the woodchips with the

small particle size and long bamboo fibers are used. On the

other hand, the impact strength is high when the woodchips

with the large particle size and long bamboo fibers are used.

(4) The proposed composite composed of woodchips, long bam-

boo fibers and the biodegradable adhesive has the high

strength, and the practical application for the composite

can be expected.

Acknowledgements

We are grateful to Mr. Masahiro Okuya in Miyoshi Oil & Fat Co.,

Ltd. and Mr. Toshiaki Ishikawa in Japan Corn Starch Co., Ltd. for

providing us with the data for the basic characteristics of the bio-

degradable adhesive Landy CP-100.

References

[1] Miki M, Takakura N, Kanayama K, Yamaguchi K, Iizuka T. Effects of forming

conditions on compaction characteristics of wood powders. Trans Jpn Soc

Mech Eng C 2003;69(678):502–8 [in Japanese].

[2] Miki M, Takakura N, Kanayama K, Yamaguchi K, Iizuka T. Effects of forming

conditions on flow characteristics of wood powders. Trans Jpn Soc Mech Eng C2003;69(679):766–72 [in Japanese].

(A) Specimens with the water absorption of about 50%

(B) Specimens with the water absorption of about 0% by drying

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Specimen No.


2

1 2 3 4 5 6 7 8

Water absorption of

specimens :50 6%

(Woodchip size: 1mm or less)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Specimen No.

1 2 3 4 5 6 7 8

Water absorption of specimens :0 5%

(Woodchip size: 1mm or less)


2

Fig. 9. Comparison of impact energy of specimens absorbed water by Charpy

impact tests.

H. Kinoshita et al./ Composites: Part B 40 (2009) 607–612 611


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[3] Miki M, Takakura N, Iizuka T, Yamaguchi K, Kanayama K. Possibility and

problems in injection moulding of wood powders. Trans Jpn Soc Mech Eng C

2004;70(698):2966–72 [in Japanese].

[4] Kinoshita H, Kaizu K, Koga K, Tokunaga H, Ikeda K. In: Proceeding of the Japan

Society of Mechanical Engineers M& M2007; 2007. CD [in Japanese].

[5] Takagi H, Ichihara Y. Effect of fiber length on mechanical properties of ‘‘green”

composites using a starch-based resin and short bamboo fibers. JSME Int J A

2004;47(4):551–5.

[6] Keller A. Compounding and mechanicalproperties of biodegradable hemp fibre

composites. Compos Sci Technol 2003;63:1307–16.

[7] Nishino T, Hirao K, Kotera M, Nakamae K, Inagaki H. Kenaf reinforced

biodegradable composite. Compos Sci Technol 2003;63:1281–6.

[8] Wambua P, Ivens J, Verpoest I. Natural fibres: can they replace glass in fibre

reinforce plastics? Compos Sci Technol 2003;63:1259–64.

[9] Ban Co., Ltd. Available from: http://www.nmt.ne.jp/~toban/.

[10] Miyoshi Oil & Fat Co., Ltd. Available from: http://www.miyoshi-yushi.co.jp/.

[11] Convertech, vol. 010. Available from: http://www.ctiweb.co.jp/cti/sinkinou/

index.html.

[12] Japan Corn Starch Co., Ltd. A catalog of CORNPOL resin.

[13] Japan bioplastics association. Available from: http://www.jbpaweb.net/.

http://www.nmt.ne.jp/~toban/http://www.miyoshi-yushi.co.jp/http://www.ctiweb.co.jp/cti/sinkinou/index.htmlhttp://www.ctiweb.co.jp/cti/sinkinou/index.htmlhttp://www.ctiweb.co.jp/cti/sinkinou/index.htmlhttp://www.jbpaweb.net/http://www.jbpaweb.net/http://www.jbpaweb.net/http://www.ctiweb.co.jp/cti/sinkinou/index.htmlhttp://www.ctiweb.co.jp/cti/sinkinou/index.htmlhttp://www.miyoshi-yushi.co.jp/http://www.nmt.ne.jp/~toban/

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