Acta Polytechnica


doi:10.14311/AP.2018.58.0292
Acta Polytechnica 58(5):292–296, 2018 © Czech Technical University in Prague, 2018

available online at http://ojs.cvut.cz/ojs/index.php/ap

EFFECT OF IMPERATA CYLINDRICA REINFORCEMENT FORM
ON THE TENSILE AND IMPACT PROPERTIES

OF ITS COMPOSITES WITH RECYCLED
LOW DENSITY POLYETHYLENE

Olusola Femi Olusunmade∗, Abba Emmanuel Bulus,
Terwase Kelvin Kashin

Department of Mechanical Engineering, University of Agriculture, Makurdi, P. M. B. 2373, Makurdi, Nigeria
∗ corresponding author: olusunmadeolusola@yahoo.com

Abstract. Composites of recycled low-density polyethylene obtained from waste water-sachets and
imperata cylindrica were produced with particulate and long-fibre unidirectional mat reinforcements.
Comparison was made of the tensile and impact properties resulting from the use of the different
reinforcement forms at 10 wt% ratio in the matrix. The results obtained from the tests carried
out revealed that tensile strength, tensile modulus, elongation at break and impact strength of the
composite with the long-fibre mat reinforcement were better than those of the one composite with
the particulate reinforcement. The better performance observed in the long-fibre mat reinforcement
could be attributed to the retention of the toughness and stiffness of the imperata cylindrica stem in
this form of reinforcement, which is lost after the stem strands are pulverized into particles. Imperata
cylindrica stem, as a natural fibre reinforcement for polymetric material is, therefore, recommended
in the long-fibre mat form. The combination of these otherwise challenging resources in composite
materials development will add economic value to them and help to reduce the environmental menace
they present.

Keywords: tensile properties; impact strength; imperata cylindrica (IC); water-sachets; composites;
particulate; long-fibre mat.

1. Introduction
Effective resource utilization as well as concern for the
environment are among the reasons many researchers
and industries are adopting the use of renewable nat-
ural fibres as replacement for synthetic fibres in a
polymer reinforcement for the development of compos-
ites [1–3]. The composites produced with the natural
fibre reinforcement of polymetric material have shown
the potential of application in many engineering appli-
cations [4] due their excellent properties (mechanical,
physical, electrical, etc). One natural fibrous plant
is imperata cylindrical, which is a perennial, with
basal leaves 3–100 cm long, 2–20 mm wide [5]. It is
an aggressive and difficult weed to control due to its
short growth cycle. It is abundant, yet unsuitable for
grazing animals and lacks good commercial value [6].
When fully mature, its overall nutrient decline and
its sharp pointed seeds and tangled awns may injure
animals and humans [7]. They also act as a collateral
host for pathogens that affect the yield of some food
crops [8]. However, imperata cylindrica is stiff and
tough [5, 9]. These properties make it promising as a
fibre reinforcement for polymers, particularly recycled
water-sachets, to produce thermoplastic composites.
This will give economic importance to the fibre and
reduce the environmental challenges posed by plastics
wastes to human and aquatic lives. However, several
factors affect the properties of composite materials,

they include: fibre ratio in the matrix [2], production
technique, chemical modification, fibre orientation
or direction, fibre type and reinforcement form [10].
There are many types and forms of reinforcement,
such as fibre, powder, and bulk. Compared to the
other types of fibre form, the powder form has the
smallest volume. According to El-Shekeil et al. [11],
the mechanical properties of kenaf fibre reinforced
polyurethane composites were influenced by the size
of the kenaf fibre. Different fibre size showed a signifi-
cant influence on the tensile and flexural properties
and impact strength. Agarwal et al., [12] reported
that a substantial improvement in the mechanical
properties can be envisaged through an addition of
fillers (either short fibre or particulate) into a nitrile
rubber. However, the addition of short fibres has been
found to be more effective. Vijay and Singha [13]
reported that with a particle reinforcement, the com-
pressive strength increases to a greater extent than
with the short and long fibre reinforcement. It was
also reported that the composite with a particle re-
inforcement has a higher load bearing capacity and
lower wear rate than those with the short and long
fibre reinforcement. This study, therefore, made a
comparative examination of the tensile and impact
properties of polymer composites produced with im-
perata cylindrica (IC) in the particulate form and
long-fibre mat form at 10 wt% ratio in the matrix.

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vol. 58 no. 5/2018 Effect of Imperata Cylindrica Reinforcement Form

Figure 1. IC Mat.

2. Materials and method
The part of the imperata cylindrica that was used
for this study is the stem and these were obtained
from Pilla village in Makurdi area of Benue State.
The growth environment of the imperata cylindrica
is tropical with an average temperature of 27 °C and
relative humidity of 82 %. The water-sachets made
from low density polyethylene (LDPE) were hand-
picked from the environment within Makurdi area of
Benue State.

2.1. Processing of the materials
The imperata cylindrica stems were harvested in
February during the dry season, which is one of the
two major season in the tropics. Subsequently, the
finer strands of the stems were handpicked and ar-
ranged into a unidirectional mat (see Figure 1). The
average diameter across the length of the strands
selected to form the mat was 3 mm. This was mea-
sured with a digital micrometre screw gauge. Tiny
threads were used to hold the IC strands together
at three different positions along the breadth of the
mat to ease its transfer into the mould without
scattering. The dimension of the woven IC mat is
285 × 200 × 3 mm. Some of the IC strands were also
ground into smaller particles. The waste water-sachets
were thoroughly washed and pulverized at Goshen
Plastics Industry, Makurdi (see Figure 2). These
pulverized waste water-sachets will be referred to as
recycled low density polyethylene (RLDPE) hence-
forth.

2.2. Preparation and characterization
of the composites

The equipment used and methods adopted for pro-
ducing and characterizing the composites were as de-
scribed by Olusunmade et al. [3]. The weight of the
IC (particulate, mat) and the RLDPE were measured
using an electronic weighing balance such that the
weight ratio of the mat in the matrix was 1:9. The
thickness of the mat (which is the diameter of the
individual strand of the IC stem) and the expected
thickness of the test specimens were responsible for
the weight ratio in this study. Both reinforcement

Figure 2. Pulverized waste water-sachets.

forms of the imperata cylindrica were used to produce
the sheets. Figures 3–5 show one of the composite
sheets produced and the test specimens. The test
specimens for the tensile test have a dumb-bell shape
with a gauge length of 30 mm, grip width of 15 mm
and thickness of 5 mm. The dimensions of the impact
test specimens are 100 × 10 × 5 mm. Three specimens
were used for each of the tests. The temperature and
relative humidity of the test environment is 22 °C and
50 %.

3. Results and discussion
3.1. Tensile properties
3.1.1. Tensile strength of the composite
Table 1 shows the average tensile strength of the com-
posites produced with the long-fibre mat and particu-
late IC compared to the RLDPE. It was observed that
there was an increase of 57.27 % in the average ten-
sile strength of the RLDPE/IC mat composite when
compared to the RLDPE and an increase of 81.23 %
when compared to the RLDPE/IC particulate com-
posite. The higher value of tensile strength observed
for the RLDPE/IC mat composite when compared to
that of the neat RLDPE and RLDPE/IC particulate
composite was due to the transfer of stress to the IC
long-fibre. A physical examination showed that the
IC stem offers great resistance to the force pulling it
along its length, due to its stiff nature, thereby increas-
ing the tensile load bearing capacity of the composite
material before fracture.

3.1.2. Tensile modulus of the composite
Table 1 shows the average tensile modulus of the com-
posites produced with the long-fibre mat and particu-
late IC compared to the RLDPE. It was observed that
there was an increase of 327.50 % in the average tensile
modulus of the RLDPE/IC mat composite when com-
pared to the RLDPE and an increase of 278.05 % when
compared to the RLDPE/IC particulate composite.
The increment in the modulus can be attributed to
the decreased deformability of the rigid interface be-
tween the IC mat/particulate and the matrix material,
which cause a reduced strain. The enhancement in the

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O. F. Olusunmade, A. E. Bulus, T. K. Kashin Acta Polytechnica

Figure 3. Finished Composite Sheet.

Figure 4. Tensile Test Specimens.

tensile modulus is also due to the fibres itself, which
have a higher stiffness than the polymer [2, 3, 14].
The IC stem is more rigid in its original form than
when pulverized into particulate, hence, there is a
more rigid polymer/IC interface in the long-fibre mat
form resulting in a higher value for the average tensile
modulus recorded for the RLDPE/IC mat composite
over the RLDPE/IC particulate composite.

3.1.3. Percentage elongation
at break of the composite

It was observed in Table 1 that there was a decrease
of 35.24 % in the average percentage elongation of
the RLDPE/IC mat composite when compared to the
RLDPE and an increase of 28.74 % when compared to
the RLDPE/IC particulate composite. With the in-
corporation of the IC mat/particulate in the polymer,
the elasticity of the composite is suppressed. The re-
duction is attributed to the decreased deformability of
the rigid interface between the IC mat/particulate and
the matrix material [2, 3]. The decrease in elongation
at break is due to the destruction of the structural in-
tegrity of the polymer by the fibres and the rigid struc-
ture of the fibres [15]. The higher value of the average
percentage elongation recorded for the RLDPE/IC
mat composite over the RLDPE/IC particulate com-
posite was as a result of the mat’s long-fibres being

Figure 5. Impact Test Specimens.

able to stretch a little further while been pulled by
tensile forces before fracture due to their length un-
like the particles, which easily separate under a load
in the matrix. The IC stem is slightly more elastic
in the long-fibre mat form than in the particulate
form.

3.2. Impact strength of the composite
Figure 6 illustrates the average impact strength of the
composites produced with the long-fibre mat and par-
ticulate IC compared to the RLDPE. It was observed
that there was an increase of 44.14 % in the average
impact strength of the RLDPE/IC mat composite
when compared to the RLDPE and an increase of
151.74 % when compared to the RLDPE/IC partic-
ulate composite. The IC stem has a foam-like inner
layer, which makes it tough and able to absorb more
impact energy before fracture. This is responsible for
the higher value of the impact strength obtained for
the RLDPE/IC mat composite. In the particulate
form, the structure is destroyed, leading to a reduction
in the toughness and hence a lesser value of the impact
strength of the RLDPE/IC particulate composite.

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vol. 58 no. 5/2018 Effect of Imperata Cylindrica Reinforcement Form

RLDPE RLDPE/IC Mat RLDPE/IC Particulate
Tensile Strength (MPa) 10.86 ± 0.86 17.09 ± 1.50 9.43 ± 0.62
Tensile Modulus (MPa) 116.44 ± 14.86 497.78 ± 33.34 131.67 ± 15.46
Elongation at Break (%) 54.93 ± 16.57 35.57 ± 8.43 27.63 ± 2.3

Table 1. Tensile properties of RLDPE, RLDPE/IC Mat and RLDPE/IC Particulate.

 

 

 

 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

RLDPE RLDPE/IC MAT RLDPE/IC PARTICLE

Im
p

a
c
t 

S
tr

e
n

g
th

 (
J
/m

m
)

Material Type

Figure 6. Comparison of Impact Strength of RLDPE,
RLDPE/IC Mat and RLDPE/IC Particulate.

4. Conclusion
In this study, composites of recycled low-density
polyethylene obtained from waste water-sachets and
imperata cylindrica were produced with particu-
late and long-fiber unidirectional mat reinforcements.
Comparison was made of the tensile and impact prop-
erties resulting from the use of the different reinforce-
ment forms at 10 wt% ratio in the matrix. The re-
sults from the tests carried out revealed that ten-
sile strength, tensile modulus, elongation at break
and impact strength of the composite with the long-
fibre mat reinforcement were better than that of
the composite with the particulate reinforcement.
The better performance observed in the long-fibre
mat reinforcement could be attributed to the re-
tention of the toughness and stiffness of the im-
perata cylindrica stem in this form of reinforce-
ment, which is lost after the stem strands are pul-
verized into particles. Imperata cylindrica stem, as
a natural fibre reinforcement for polymetric mate-
rial is, therefore, recommended in the long-fibre mat
form.

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	Acta Polytechnica 58(5):292–296, 2018
	1 Introduction
	2 Materials and method
	2.1 Processing of the materials
	2.2 Preparation and characterization of the composites

	3 Results and discussion
	3.1 Tensile properties
	3.1.1 Tensile strength of the composite
	3.1.2 Tensile modulus of the composite
	3.1.3 Percentage elongation at break of the composite

	3.2 Impact strength of the composite

	4 Conclusion
	References