This research studied the potential of renewable material, corncob, as a composite with starch binder to produce green particleboard. The starch was used as a binder in stead of binder from formaldehyde. The corncob and starch binder composite was prepared using compression molding at ratio between the composite was 9:1, 8:2, 7:3 and 6:4 respectively. The increase of concentration of starch binder increased density and tensile strength of composite. The result of water absorption of composite decreased with higher binder content. As a natural material, it was shown that the mechanical performance of corncob and starch binder composite could be tailored to reproduce the behavior of green particle boards

1. MECHANICAL AND PHYSICAL PROPERTIES OF GREEN
PARTICAL BOARD PRODUCE FROM CORNCOB AND STARCH
BINDER COMPOSITE
Prayoon Surin, Jessada Wong-on* and Penlapus Yimsamerjit
Department of Industrial Engineering, Pathumwan Institute of Technology
833 Rama I Rd., Pathumwan, Bangkok 10330 Thailand
*rabit_in_themoon@yahoo.com
ABSTRACT
This research studied the potential of renewable material, corncob, as a composite with
starch binder to produce green particleboard. The starch was used as a binder in stead of
binder from formaldehyde. The corncob and starch binder composite was prepared using
compression molding at ratio between the composite was 9:1, 8:2, 7:3 and 6:4 respectively.
The increase of concentration of starch binder increased density and tensile strength of
composite. The result of water absorption of composite decreased with higher binder
content. As a natural material, it was shown that the mechanical performance of corncob and
starch binder composite could be tailored to reproduce the behavior of green particle boards.
KEY WORDS: Green particleboard, Composite, Corncob, Starch binder
1. INTRODUCTION
Plant-based or bio composites may become materials to replace polymer based
composites and wood in terms of their attractive specific properties, lower cost, simple
processing technologies, eco-friendliness, and ability to be recycled after use.
Environmentally sustainable lignocellulosic resources are available in different forms of
non-wood based fibers and agricultural residues. Non-wood commercial fibers include jute,
sisal, kapok, kenaf, flax, hemp, ramie, etc. Agriculture residues include stalks of most cereal
crops, rice husks, coconut fibers (coir, bagasse, maize cobs, peanut shells, and other wastes.
Man has a long history of using non-wood lignocellulosic resources for producing
composites [1]. These materials have economical and environmental advantages over
petroleum-based materials, making them an attractive alternative.
Particleboard is a panel product manufactured from lignocellulosic materials, primarily in
the form of discrete particles, combined with a synthetic resin or other suitable binder and
bonded together under heat and pressure. Resin is sprayed through nozzles onto the
particles. The major types of particles used to manufacture particleboard include wood
shavings, flakes, wafers, chips, sawdust, strands, slivers, and wood wool. Synthetic

2. thermosetting resins are used to bond the fibers together and other additives may be used to
improve certain properties. There are several types of resins which are commonly used. Urea
formaldehyde resin is the cheapest and easiest to use. It is used for most non-water resistant
boards. Melamine formaldehyde resin is significantly more expensive, as it is moisture
resistant. Phenol formaldehyde is also fairly expensive [2]. The major disadvantage
associated with urea formaldehyde adhesives is the lack of resistance to moist conditions,
especially in combination with heat. These conditions lead to a reversal of the bond-forming
reactions and the release of formaldehyde. The formaldehyde emission levels of products
bonded with urea-formaldehyde adhesive resin, the industry still faces the possibility of
more restrictive regulations on formaldehyde in dwellings. Moreover, tighter restrictions on
formaldehyde levels in the workplace are also likely [3].
Bio-base material or bio composite provided of ensuring long-term service of material in
hazardous environments. Natural products have attracted interest due to health risk and
environmental problem associated with the application of chemical wood preservatives [4].
In the recent past, increasing attention has been paid to the use of natural adhesives as a
binder in the wood-based panel industry such as spruce tannin as a binder for medium
density fiberboards [5], lignin based adhesive [6] or wheat starch [7].
This research studied a natural material, corncob; the central wooden core of a maize,
composite with cassavas starch binder (starch-based material) with low toxicity, high
biodegradability and availability, as substitutes of synthetic thermosetting materials used as
binders for green particleboard production.
2. MATERIALS AND METHODS
2.1. Board Manufacture
Corncob was smashed and screened to separate the dust and small particles 2-4 mm.
Corncob was dried at 80- 90 °C until 9.5% moisture content. Dry corncob were mixed with
cassavas starch binder before pressing at 160 °C for 5 min under 20 kg/cm2
pressure to
produce test boards 50°50 mm in size and 10 mm in thick. The corn and starch binder ratio
was used at 9:1, 8:2, 7:3 and 6:4 respectively.
2.2. Mechanial Testing
Composites from the model formation were tested for tensile strength by standard ASTM
D1037-99.
2.3. Physical Testing
Density and dimension stability were measured by ASTM D1037-99.
3. RESULT AND DISCUSION
3.1 Physical properties
3.1.1 Density
The results from density test of corncob and starch binder composite was shown in
Fig. 1 Density of the composites trended to increase when starch binder content increased.
The increase of density was attributed to good adhesion between corncob and starch binder.
Starch can make substantial contributions to the composite properties by acting as increasing
adhesion between corncob matrixes [8]. The highest density was 2.26 g/cm3
at 30 weight
percent binder. The decrease of density at 40 weight percent of binder was a less dense of
composite when higher starch binder. Density of material influenced on strength and

3. stability of material. Maloney [9] reported that increase of particleboard density improves
the physical properties.
0
0.5
1
1.5
2
2.5
10 20 30 40
Starch binder content (wt%)
Density
(g/cm
3
)
Fig. 1 Density of corncob and starch binder composites at 10-40 wt% binder content
3.1.2 Water Absoption and Dimension stability
Dimension stability and water absorption is important properties of particleboard
composite. This research studied dimension stability of the corncob and starch binder
composite based on thickness swelling. The particleboard composite was soaked in water for
2 hours. The result of thickness swelling was shown in Fig. 2 The particleboard composite is
shown in Fig. 3 Thickness swelling of the particleboard composite decreased when starch
binder content increase. More fibrous material was absorbed much water. If the
particleboard composite was compressed so that there was greater contact between the
particles in the matrix, the starch binder was cured more effectively in the void spaced of the
particleboards and there less water absorption. Thus the fiber absorbed much water result in
higher thickness swelling whereas water absorption decreased. This behavior was also found
by Mustafa et al [4].
0
20
40
60
80
100
10 20 30 40
Starch binder content (wt%)
Thicness
swelling
(%)
Fig. 2 Percentage of thickness swelling of corncob and starch binder composites
at 10-40 wt% binder content

4. 40 30 20 10
Fig. 3 corncob and starch binder composites at 10-40 wt% binder content
3.2 Mechanical Properties
0
20
40
60
80
100
120
140
160
10 20 30 40
Starch binder content (wt%)
Tensile
Strength
(kgf/mm
2
)
Fig. 4 Tensile strength of corncob and starch binder composites at 10-40 wt%
binder content
Fig. 4 showed tensile strength of the particleboard composite, corncob and starch binder.
Tensile strength of the particleboard composite increased when starch binder content
increased. The highest tensile strength of the particleboard composite was 141 kgf/mm2
at
30 weight percent binder content. This result indicated that better adhesion between corncob
and starch binder increased tensile strength of the particleboard composite. The strength
reduction was obtained at 40 weight percent binder content. At this point it was more binder
and less corncob content which was lower fiber part and weak for tensile strength [10].
4. CONCLUSION
The cassavas starch binder was used in stead of synthetic formaldehyde resin. It was non
toxic binder. The results of this work showed that it is possible to use starch as a binder
replace for hazardous synthetic resins. The highest tensile strength of the particleboard
composite was 141 kgf/mm2
at 30 weight percent of starch binder. The binder increased
density of the composites whereas decrease thickness swelling. The starch binder has
potential as a binder with a renewable agricultural material, corncob, for making green
particleboard.
5. REFERENCES
[1] http://www.springerlink.com/content/ ep314051gh428143/fulltext.pdf
[2] http://www.epa.gov/ttn/chief/ap42/ch10/ final/c10s06-2.pdf
[3] http://www.fpl.fs.fed.us/documnts/pdf1996/ conne96a.pdf
[4] M. K. Yalinkilic, International Biodeterioration & Biodegradation, 41, 75-83 (1998)

5. [5] http://www.springerlink.com/content/ 9jmwhx8u31d0etq0/fulltext.pdf
[6] http://journals.tubitak.gov.tr/agriculture/issues/tar-03-27-3/tar-27-3-8-0205-10.pdf
[7] http://www.touchbriefings.com/
[8] http://www.chemistry.mtu.edu/pages/courses/files/ ch4620-paheiden/WebProject-
2006/Bio%20Project/ Bio-1.pdf
[9] T. M. Maloney, Modern Particleboard & Dry-Process Fiberboard Manufacturing, Miller
Freeman Inc., San Francisco, 1993, pp 681.
[10] R. Viswanathan, Gothandapani, Biores. Technol., 67, 93-95 (1999)