Journal of Engineering (Issue on Mechanical, Materials and Manufacturing Engineering)

Mechanical Properties of Medium Density Fibreboard Composites

Material Using Recycled Rubber and Coconut Coir
S. Mahzan*, A.M. Ahmad Zaidi, M.I. Ghazali, N.Arsat, M.N.M. Hatta and S. Rasool Mohideen
Faculty of Mechanical and Manufacturing Engineering, UTHM
*Corresponding email: sharudin@uthm.edu.my

Abstract
Natural fibre reinforced composite has emerged as highly potential replacement for synthetic
fibres. Various natural waste fibres have been adopted for various engineering applications. This
paper investigates the mechanical properties of medium density fibreboard composites material
fabricated using recycled rubber and coconut coir. The suitability of using recycled rubber and
coconut coir as a raw material and polyurethane as a resin in the manufacturer of medium density
fibreboard was also studied. The medium density fibreboards were fabricated at prescribed
percentages of filler. The performance of composite was evaluated by its mechanical and physical
properties. Experimental investigation indicated that the mechanical strength of medium density
fibreboards such as modulus of rupture and modulus of elasticity increased with increasing board
hardness. Overall, the results showed that medium density fibreboard had been produced with
acceptable properties, thus providing alternatives to manufacturing and agricultures economic
planning.

Keywords: Coconut coir, Mechanical Properties, Medium Density Fibreboard, Recycled Rubber.

21
 Journal of Engineering (Issue on Mechanical, Materials and Manufacturing Engineering)

1. INTRODUCTION 2. MATERIALS AND METHODS

The uses of natural fibres in various 2.1 Materials
applications have received considerable The study utilised coconut coir and recycled
attentions to many researchers. Normally, rubber as the fillers, whereas polyurethane was
waste natural materials are burned or dumped, chosen as the resin. Polyurethane is selected
thus creating environmental problems. There due to its structural versatility, e.g.
have been efforts to utilise these waste thermosetting, thermoplastic, rigid, elastomer,
materials for something beneficial to human. and flexible. They are also more compatible to
These include waste materials from tea –leaf fibre compared to other resins, due to possible
fibre, coconut fibre and rice wood [1-3]. The reaction of hydroxyl groups of the fibres and
research focuses on sound absorption panel the isocyanate groups of the polyurethane.
that can be used in various applications. Initially, the coconut coir and recycled
Another investigation focuses on producing the rubber need to undergo pre-processing stages
medium density fibreboard that can be applied before they can be used to form MDF
for furniture, cupboards and flooring. composite. For instance, coconut coir need to
Medium density fibreboard (MDF) is made be grinded to produce small grains, soaked in
from lignocellulosic fibres combined with a water, washed and dried. Similarly, recycled
synthetic resin or other suitable bonding rubber needs to be cut into small particles.
system that are combined together under heat Here, a recycled tyre tube was used as the
and pressure [4,5]. MDF is denser than sample. These two materials are then equally
plywood or particle boards hence widen its mixed together with the polyurethane as the
applications. Reinforcing a polymer matrix binder, at prescribed percentages, as shown in
with lignocellulosic materials have been Table 1 and 2. Here, the percentage of
attributed to several advantages such as lower polyurethane varies in order to investigate the
density, high stiffness, less abrasive to influence of resin on the performance of
equipment, biodegradable and lower cost [6-7]. coconut coir composites.
The However, the major concern in producing
good lignocelluloses–thermoplastics Table 1: Composition of coconut coir, recycled
composites, especially in term of mechanical rubber with 25 percents of polyurethane
and physical properties, the compatibility Sample Coconut Coir (%) Tube tyre (%)
between the constituent materials should have 1 0 100
been resolved. 2 10 90
In general MDF uses wood based fibres as 3 20 80
the raw material and urea formaldehyde as the
4 30 70
resin. However, the decreasing in wood supply
and health hazard produced by urea 5 40 60
formaldehyde are of concerned. Alternative
material is needed for replacement to Table 2: Composition of coconut coir, recycled
conventional material. One of the potential rubber with 35 percents of polyurethane
natural wastes is coconut coir fibres. The Sample Coconut Coir (%) Tube tyre (%)
coconut coir fibre contains a high lignin ratio 1 0 100
and thus low cellulose content, as a result of 2 10 90
which it is resilient, strong and highly durable. 3 20 80
That makes this fibres stiffer and tougher [8-9]. 4 30 70
This paper investigates the viability of 5 40 60
coconut coir fibre added with recycled rubber
as the potential material for MDF. The effect The mixture were then pressed for 15
of adding recycled rubber particles and the minutes using the hot press machine at 90°C
influence of polyurethane are investigated as with 10 tonnes of pressure to produce
the potential replacement of synthetic and composite board, as demonstrated in Figure 1.
mineral fibres.

22
 Journal of Engineering (Issue on Mechanical, Materials and Manufacturing Engineering)

about porosity, void spaces between fillers and

resin and the surface textures of the MDF
composite can be identified.

2.3 Mechanical properties

The MDF composite was also tested for its
mechanical properties, e.g. hardness and
bending tests. The Shore Hardness (Durometer
Hardness) is measured by determining the
Fig. 1 Sample of coconut coir – recycled rubber depth of penetration of the indenter in the
composite fibre board material being tested. This measurement is
then transmitted to a linear scale in increments
2.2 Physical properties of 0 to 100, which one increment equals to one
The physical properties measured for MDF hardness point. The hardness tests were
composites consist of four tests, e.g. porosity, performed according to standard of D 2240.
density, water absorption and microstructure Bending strength from three points was done
tests. Porosity is a measure of the void spaces according to ISO 178:93 by a SHIMADZU
in a material, normally calculated as the Universal Testing Machine (Model AG-1).
fraction of the voids volume over the total These tests were carried out to determine the
volume. The porosity value is denoted in modulus of rupture (MOR), and the modulus
range, between 0–1, or as a percentage of elasticity (MOE). Charpy impact test with 4
between 0–100 percents; of which zero value J loads was performed on the MDF composite
indicates no pores is existed, whereas value 1 board to measure its impact strength. The
or 100% indicates total pores is existed. composite samples were cut into 8cm length,
Density is a physical property of matter, as 2cm width and 1cm thick. The impact strength
each element and compound has a unique was calculated by dividing the impact energy
density associated with it. Density is defined in with the cross-sectional area of the specimen.
a qualitative manner as the measure of the
relative "heaviness" of objects with a constant 3. RESULTS AND DISCUSSION
volume. Density plays an important indicator 3.1 Physical properties
of a composite’s performance, where it Figure 2 demonstrates the experimental
virtually affects all properties of the material. result obtained for porosity test. It shows that
Moisture content was examined using the porosity value is increased when the
ASTM D 1037-99 (American Society for percentage of coconut coir is increased. It is
Testing and Materials, 1999) method. also demonstrates that sample 5 with 40
The water absorption was determined by percents of coconut coir and 60 percents of
weighting the samples at regular intervals. A recycle rubber have the highest porosity value.
Mettler balance type AJ150 was used with a
precision 0f ± 1 mg. The percentage of water
absorption, Mt was calculated by where Wd
and WN are original dry weight and weight
after exposure, respectively. Equation (1)
shows the relationship of water absorption for
MDF composite.

W N  Wc
Wt   100% (1)
Wd
Fig. 2 Values of porosity for various percentages
Finally, in order to ascertain the property of of coconut coir and recycled rubber
MDF composite, the microstructure of the
sample is observed. Here, characteristics of
fillers (coir and rubber) and the resin is
determined using scanning electron
microscopy (SEM), where the information
23
 Journal of Engineering (Issue on Mechanical, Materials and Manufacturing Engineering)

Fig. 3 Values of density for various percentages Fig. 4 Values of moisture contents for various
of coconut coir and recycled rubber percentages of coconut coir and recycled rubber

Variations of densities, e.g. 25 and 35

percents of polyurethane were recorded for
five different samples as demonstrated in
Figure 3. The trend shows the decreasing
pattern, with 25 percents yielded lower values
for all samples compared to 35 percents of
polyurethane. The results also indicated that
density values of fibreboard are related to the
percentage content of fillers. The density
values are gradually decreased as the
percentage of recycled rubber is decreased or
percentage of coconut coir is increased. It was Fig. 5 Values of water immersion for various
anticipated that the increased in recycled percentages of coconut coir and recycled rubber
rubber percentages is reducing the pores in the
samples. Again, sample 5 demonstrated the Water immersion test of the composites
lowest density with 219.9 g/cm3. reveals the behaviour of the composites, with
Figure 4 showed the comparison of moisture respect to percentage of water absorbed. The
content between different percentage of filler result shows in Figure 5 indicated that the
and resin. The moisture contents of the water absorption decreased when the recycled
composite boards ranged from 0.54 to 0.99 % rubber is decreased or the coconut coir is
wt. %. It is observed that sample 5 produced increased. This is expected because the
the highest moisture contents at about 0.99 characteristic of coconut coir being a
percents. The increasing trend was observed lignocelluloses material readily absorbs water
that the coconut coir content linearly increased into its cell wall through the formation of
with the increase of moisture content. It is due hydrogen bonding between its OH groups and
to coconut coir has a good characteristic in the H from water. However, there is no
water absorption. On contrast, tyre tube is not significant difference in water absorption
performing well in water absorption. In among the composites with various
overall, MDF composite is suitable to be percentages of filler.
applied in industry since the moisture content
recorded was below 3 percents. 3.2 Mechanical properties
Figure 6 and 7 show the hardness values
obtained for 25 and 35 percents of
polyurethane, respectively. Both graphs
demonstrate a linearly upward trend, with the
hardness increased when the percentage of
coconut coir is increased or recycled rubber is
decreased. Sample 5 that contains 40 percents
of coconut coir and 40 percents of recycled
rubber demonstrated the highest values.

24
 Journal of Engineering (Issue on Mechanical, Materials and Manufacturing Engineering)

of proportional limit. Like MOR, the same

trends also display by flexural modulus (MOE)
results as shown Fig. 9. Generally it can be
seen that irrespective percentage of the coconut
coir increased and tube tyre decreased, the
MOE of composites was increased. This
indicates that the more addition of percentage
fibre into the board was affected MOE results
through the adhesive binding on the filler. The
MOE value increases as the fibre increase,
because the inherent stiffness of the fibre may
Fig. 6 Hardness value for PU 25% and Filler positively contribute to the overall stiffness of
75% the boards.

Fig. 7 Hardness value for PU 35% and Filler Fig. 9 Values of density for various percentages of
65% coconut coir and recycled rubber

Referring to Figure 10, it can be seen that the

The bending modulus of rupture (MOR) of Charpy impact strength of fibreboard goes up
the MDF coconut coir and tube tyre is shown approximately from 4.13 to 4.95 kJ/m2 as the
in Fig.8. Bending MOR increased slightly with coconut coir is increased from 0 to 40 percents.
the increased percentage of coconut coir or Impact behaviour is a measure of the energy
decreased in recycled rubber percentage. required to cause damage and the progress
Increasing fibres in MDF content increases the failure within the composite. Any enhancement
flexural strength, as demonstrated by sample 5. in toughness and stiffness due to the presence
The recorded flexural strength was 4.47 MPa of natural fibres must rely upon the fibre
for MDF with 25 percents of polyurethane. matrix bond or the inherent toughness and
stiffness of the fibres themselves. Moreover,
the resin and fibre content might also influence
the impact strength significantly. At higher
resin and fibre content, it more covalent bonds
and crosslink would from between fibre and
resin. The former is common in composites
with strong interfacial bond while the
occurrence of the letter is a sign of a weak
bond. With the chemical treatments has been
reported to reduce the impact strength, so it can
produce a good bond. This might resist the
deformation of interface between resin and
Fig. 8 Values of modulus rupture for various fibre, resulting in tougher fibreboard. Another
percentages of coconut coir and recycled rubber reason must be the crosslink density of the
MDF used. The low crosslink density MDF is
The bending modulus of elasticity (MOE) is far more readily toughened than the high
the slope of the tangent line at the stress point crosslink density MDF.
25
 Journal of Engineering (Issue on Mechanical, Materials and Manufacturing Engineering)

Tube

Matrix
Coconut

Fig. 10 Values of impact strength for various

percentages of coconut coir and recycled rubber
Fig. 12 Microscopic view for composite board with
3.7 Morphological 35 percents of polyurethane

Tube 4. CONCLUSION
The mechanical and physical properties of
medium density fibreboard (MDF) composites
Coconut based on coconut coir and recycled rubber
Matrix were successfully obtained. It was found that
the content of fillers and resins play an
important role in order to get good results.
Here, the optimum composition was 40
percents of coconut coir added with 60
percents of recycled rubber. The new MDF
composites combine cheap and highly
available raw materials with have quite good in
Fig. 11 Microscopic view for composite board with final properties is important to remark. The
25 percents of polyurethane performance of such materials may be
enhanced by improving the adhesion between
The density and porosity properties of the both co-components. The lack of affinity
composite fibre boards were controlled by the between natural filler and recycled rubber may
gas quantity released during the isocyanate be improved by choosing an adequate
reaction. This affects the number of cells and compatible stabilizing agent. The usage of the
their sizes. Figures 11 and 12 compare the MDF as filler also demonstrated a good result
surface structure between composites with 25 due to the MOE, MOR, impact strength,
and 35 percents of PU content, respectively. It hardness, moisture content, porosity, and
was observed that more pores have occurred in density properties of the fibreboard. Therefore
the sample with 25 percents PU with larger this material make either alternative to reduce
pore size. The recorded pore size obtained was pollution rate and achieving mechanical and
between 129µm to 179µm. On contrary, physical properties desired for many
composite boards with 35 percents PU and 65 application such as interior lining for
percents fillers produced less pores and smaller apartments, aircrafts, ducts, enclosures, sub
pore sizes. The measured size recorded was in flooring, interior surface for wall which can to
between 99µm to 110µm. The microstructure reduce the reverberant.
of composite fibre boards justifies the results
obtained in density and porosity analysis, and
reflecting into the acoustics properties of
coconut coir composite boards.

26
 Journal of Engineering (Issue on Mechanical, Materials and Manufacturing Engineering)

REFERENCES
[1] R. Zulkifli, Zulkarnain and M.J.M. Noor,
2010. “Noise control using coconut coir
fibre sound absorber with porous layer
backing and perforated panel”, American
Journal of Applied Sciences, Vol. 7(2), pp.
260-264.
[2] S. Ersoy and H. Kucuk, 2009.
“Investigation of Industrial tea-leaf-fibre
waste material for its sound absorption
properties”, Applied Acoustics, Vol. 70, pp.
215-220.
[3] H-S.Yang, D.-J.Kim and H.-J. Kim, 2003.
“Rice straw-wood particle composite for
sound absorbing wooden construction
material”, J. Bioresource Tech., Vol. 86,
pp. 117-121.
[4] ANSI Standards, A208.2-1994. Medium
Density Fiberboard (MDF). National
Particleboard Association, Gaithersburg,
MD. 1994.
[5] P. Douglas, W.R. Murphy and G.M.
McNally, “The effect of surface active
agent on the mechanical properties of
wood-polymer composites”, Queen’s
University Belfast.
[6] R. M. Rowell, B. A. Cleary, J. S. Rowell,
C. Clemons and R. A. Young. “Results of
chemical modification of lignocellulosic
fibers for use in composites”, in Wood –
fiber/polymer composites: Fundamental
concepts, processes and material options,
Forest Products Society, 1993, pp. 121–
127.
[7] M. Jacob, S. Thomas and K.T. Varughese.
“Mechanical properties of sisal/oil palm
hybrid fiber reinforced natural rubber
composites”, J. Comp. Sci. and Tech.,
2004. Vol. 64, pp. 955-965.
[8] H.P.S Abdul Khalil, M. Siti Alwani,and
K.Mohd Omar, “Chemical composition,
anatomy, lignin distribution and cell wall
structure of Malaysia plant waste fibres”.
BioResources, 2006, Vol 1 (2), pp. 220–
232.
[9] A.A. Erakhrumen, S. E. Areghan, M. B.
Ogunleye, S. L. Larinde and O. O.
Odeyale, “Selected physico-mechanical
properties of cement bonded particleboard
made from pine (Pinus caribaea M.)
sawdust-coir (Cocos nucifera L.) mixture”,
Scientific Research and Essay, 2008, Vol.
3 (5), pp. 197 – 203.

27
International Journal of Integrated Engineering (Issue on Mechanical, Materials and Manufacturing Engineering)

28