American Journal of Polymer Science 2012, 2(4): 56-61

DOI: 10.5923/j.ajps.20120204.02

Studies on Properties of Egg Shell and Fish Bone Powder

Filled Polypropylene
Isaac O. Igwe*, Genevive C. Onuegbu

Department of Polymer and Textile Engineering, Federal University of Technology, Owerri, Nigeria

Abstract The mechanical and end-use properties of egg shell and fish bone powder filled polypropylene have been de-
termined at filler contents, 0 to 40 wt. %, and particle sizes, 0.150, 0.30, and 0.420 µm. Talc, of particle size, 0.150 µm was
used as the reference filler. The incorporation of egg shell and fish bone powder into polypropylene resulted in improvement
in the tensile strength, tensile modulus, flexural, and impact strength of the composites, and these properties increased with
increase in filler contents, and decrease in filler particle sizes. The elongation at break of the composites was observed to
decrease with increase in filler contents, and particle sizes. The hardness, specific gravity, and water absorption (24 h) of the
prepared composites were found to increase with increase in filler contents, and decease in filler particle size. Talc filled
polypropylene was observed to absorb less water than fish bone or egg shell powder filled polypropylene. The amount of
water absorbed by these composites was observed to be independent of filler content or particle size but on the nature of the
filler used. The fillers under investigation efficiently reduced the rate of burning of polypropylene at high filler contents, and
particle sizes. Generally, egg shell, and fish bone powder fillers have shown greater property improvement over talc in the
prepared composites. Egg shell, and fish bone powder fillers could be viable alternatives to the conventional mineral fillers
for the plastic industry, and for applications where the high water absorption of the fillers is not a critical factor of interest.
Keywords Polypropylene, Composite, Mechanical and End-Use Properties, Filler, Egg Shell and Fish Bone Powder,
Filler Particle Size, Talc

tremendous impact in lowering the usage of petroleum-based

1. Introduction plastics. Filler particles form aggregates or agglomerates
with increasing volume fraction and this depends on their
Polypropylene is one of the most important polyolefins surface energy, and area. The mechanism of polymer rein-
that have a wide range of applications. The use of filled forcement by fillers is not yet fully understood, and is the
polypropylene in electrical and automotive engineering is subject of many publications in the scientific literature[3-5].
presently on the increase due to its excellent stiffness prop- Generally, the properties of filled polymers change with the
erty. Like any other polyolefin, polypropylene is widely dispersion state, geometrical shape, and surface quality of
exploited but not used as a neat polymer. To enhance the the filler particles as well as the particle size.
properties of polyolefins, they are frequently compounded The outlook for filled polypropylene is becoming brighter
with natural minerals (fillers). due to the recent commercial availability of nanosized fillers.
Fillers which merely increase the bulk volume and hence, Nanocomposite materials with length scales smaller than
reduce price, are known as extender fillers while those which 1µm are becoming important as the size of modern electronic
improve mechanical properties, particularly tensile strength devices reaches down to the submicron scales. Typical fillers
are termed as reinforcing fillers[1]. Several million metric for polypropylene are glass fibres, glass sphere, talc, as-
tons of fillers and reinforcements are used annually by the bestors, silica, and mica. The use of mineral fillers and fibres
plastic industry. The use of these addictives in plastics is in making polymer composites has its disadvantages. For
likely to grow with the introduction of improved com- example, a lot of energy is used in the processing of glass
pounding agents that permit the use of high filler/ rein- fibres since their processing temperatures can exceed 1200℃.
forcement content[2]. It has been suggested that fillings up to Also, glass fibres tend to abrade processing equipments, and
75 parts per hundred (pph) could be a common practice in increase the density of the plastic system[6].
future, and that this level of filler addition could have a In the literature, different materials have been studied to
fill polypropylene. These materials include saw dust[7],
* Corresponding author:
izikigwe@yahoo.com (Isaac O. Igwe)
wood flour[8], flax fibre[9], hemp strands[10], flax pulps
Published online at http://journal.sapub.org/ajps [11], lyocell fibre[12], green-coconut fibre[13], montmoril-
Copyright © 2012 Scientific & Academic Publishing. All Rights Reserved lonite[14,15], calcium carbonate[16,17], magnesium hy-
57 American Journal of Polymer Science 2012, 2(4): 56-61

droxide[18], and snail shell powder[19]. shell, and fish bone powder were produced were collected
Recently, Yunus et al[20] prepared carbon fibre - poly- locally within Owerri Metropolis, Imo State, Nigeria. These
propylene composites under various process conditions, and materials were properly treated to remove impurities before
determined the mechanical properties of the prepared com- they were crushed and sieved to three particles sizes namely,
posites. The highest tensile strength was obtained for poly- 0.150, 0.30, and 0.42 µm. Talc, which was used as the ref-
propylene (MFI 60) composites reinforced with 10 wt.% erence filler was purchased from a local store at Owerri, Imo
carbon fibre. The composites also exhibited the best tensile, State, Nigeria.
and flexural properties. Also, Wang et al [21] prepared
nano-CaCO3/homo – polypropylene composites by melt - 2.2. Preparation of Polypropylene Composites
blending using twin – screw extruder. The results showed The polypropylene composites of egg shell (ESP), and
that both the impact property and bending modulus of the fish bone powder (FBP) were prepared as described previ-
composites were evidently increased on addition of ously for snail shell powder composites of polypropylene
nano-CaCO3. The electron-beam preirradiation and reactive [23]. The polypropylene composites of talc were prepared
extrusion technologies were used to prepare maleic anhy- only at filler particles size, 0.150 µm.
dride (MAH)/ vinyltrimethoxysilane (VTMS) –co-grafting
polypropylene(PP) as a high-performance compatibilizer for 2.3. Testings
wood-flour/PP composites [22]. The experimental results Testings on the mechanical and end-use properties of
demonstrated that MAH/VTMS-g-PP markedly enhanced polypropylene composites were carried out as described
the mechanical properties of the composites. Compared with previously using standard procedures[23].
MAH-g-PP and VTMS-g-PP, MAH/VTMS-g-PP clearly
showed synergistic effects on increasing the mechanical
properties, water absorption, and compatibility of the com- 3. Results and Discussion
posites.
The use of egg shell powder to fill polypropylene has also 3.1. Mechanical Properties
been reported[20]. Polypropylene composites of egg shell
3.1.1. Tensile Strength
powder were prepared at filler contents, 0 to 5 wt. %, and
particle size, 0.30 µm. The properties of the composites The effects of egg shell and fish bone powder contents,
determined were the specific gravity, water sorption (24 h), and particles sizes on the tensile strength of polypropylene
flammability rate, and hardness tests. are illustrated in Figure 1. From Figure 1, it is evident that
In the present report, the effects of incorporating egg shell the tensile strength of polypropylene composites increased
(ESP), and fish bone powder (FBP) as fillers on the me- with increase in egg shell, and fish bone powder contents.
chanical and end-use properties of polypropylene were Onuegbu and Igwe[19] who studied snail shell powder/
studied. The central objectives are to (i), investigate fully the polypropylene system reported increases in tensile strength
properties of polypropylene composites of egg shell and fish of polypropylene with increase in snail shell powder content.
bone powder, and (ii), determine the effects of egg shell, and Figure 1 shows that the tensile strength of egg shell, and fish
fish bone powder particles sizes on the properties of poly- bone powder filled polypropylene was higher than that of
propylene composites. Filler contents of 0 to 40 wt. % were talc filled polypropylene at filler particle size, 0.150 µm.
used in this study. It is important to note that the work re- Figure 1 also shows that the smaller the particle size of the
ported on the utilization of egg shell powder to fill poly- filler, the higher the tensile strength of polypropylene com-
propylene[23] was exploratory and limited in scope. posites. The envisaged better dispersion of the smaller sized
Egg shell and fish bone are domestic wastes and could be filler in the polypropylene matrix, and improved filler-matrix
found littering dustbins in our big cities, and farm yards in interaction may be the factors responsible for the observed
villages. Besides the work reported above on egg shell trend. Similar observations on the variation of composite
powder[23] which was exploratory and limited in scope, the strength with filler particle size have been reported by Bigg
use of egg shell or fish bone to fill polypropylene or any [24], and Fuad et al [25] for other filled polymer systems.
other thermoplastic has not been reported in the scientific At any particle size of the fillers investigated, the order in
literature to our knowledge. the improvement of tensile strength of polypropylene com-
posites is fish bone > egg shell powder.

2. Materials and Methods 3.1.2. Tensile Modulus

The tensile modulus of filled and unfilled polypropylene
2.1. Materials
are illustrated in Figure 2. Figure 2 shows that the modulus of
The polypropylene used in this study was obtained from polypropylene composites were higher than the modulus of
Eleme Petrochemical Company Limited, Rivers State, Ni- unfilled polypropylene, and increased with increase in filler
geria. It has a melt flow index of 2.5 to 3.5 g/min, and density, content. This observation highlights the fact that the incor-
0.926 g/cm3. The egg shell, and fish bone from which egg poration of fillers into polymer matrix improves the stiffness
 Isaac O. Igwe et al.: Studies on Properties of Egg Shell and Fish Bone Powder Filled Polypropylene 58

of the latter. The result obtained in this study is in agreement hancement of the flexural strength of polypropylene com-
with the findings of Rozman et al[26] who working on oil posites is fish bone > egg shell powder, and at 0.150 µm filler
palm empty fruit bunch powder - polypropylene system particle size considered, the order is fish bone powder > egg
found that the tensile modulus of polyethylene composites shell powder > talc. This order shows that egg shell, and fish
increased with increase in oil palm empty fruit bunch powder bone powder are better fillers than talc in enhancing the
content. Similarly, Onuegbu and Igwe[19] had reported an flexural strength of polypropylene.
increase in tensile modulus of polypropylene on addition of
snail shell powder. Both egg shell, and fish bone powder
enhanced the tensile modulus of polypropylene more than
talc, the reference filler (Figure1). However, fish bone
powder was superior to egg shell powder in increasing the
tensile modulus of polypropylene.

Figure 3. Plot of Flexural Strength versus Weight of Filler for Polypro-

pylene Composites at different Filler Particle Sizes

3.1.4. Elongation at Break

Elongation at break (EB) is a measure of the ductility of a
material. The data on elongation at break obtained for poly-
propylene composites at different filler contents, and particle
Figure 1. Plot of Tensile Strength versus Weight of Filler for sizes are illustrated graphically in Figure 4. The figure shows
Polypropylene Composites at different Filler Particle Sizes
that the EB of polypropylene composites decreased with
increase in the filler contents at any filler particle size con-
sidered. Fillers, generally can be considered as structural
elements embedded in the polymer matrix, and at the con-
centrations of the fillers used (0 to 40 wt. %), the concentra-
tions might not be high enough to significantly restrain the
polypropylene molecules. Consequently, highly localized
strains might have occurred at the concentrations investi-
gated, causing dewetting between polypropylene and the
fillers, and thus, leaving essentially a matrix that is not duc-
tile. Such a reduction in elongation at break of polypropylene
composites on addition of fillers has been reported by
Onuegbu and Igwe[19], Fuad et al[25], and Basuki et al[27].

Figure 2. Plot of Tensile Modulus versus Weight of Filler for Polypro-

pylene Composites at different Filler Particle Sizes

3.1.3. Flexural Strength

The experimental data on the flexural strength of poly-
propylene composites are illustrated graphically in Figure 3.
It is evident that at any particle size of the fillers considered,
the flexural strength of the composites increased with in-
crease in filler contents. Figure 3 also shows a general de-
crease of flexural strength of the composites as the particle
size of the fillers increased from 0.150 to 0.420 µm. Similar
decrease in material property with increase in filler particle
size was also observed for the tensile strength and tensile Figure 4. Plot of Elongation at Break versus Weight of Filler for Poly-
modulus of the composites. The general order in the en- propylene Composites at different Filler Particle Sizes
59 American Journal of Polymer Science 2012, 2(4): 56-61

It is important to note that the EB of polypropylene 3.2.1. Hardness

composites decreased with increase in filler particle size. Figure 6 shows the effect of filler contents and particle
Firstly, there is the envisaged better dispersion of the smaller sizes on the hardness of filled polypropylene. The hardness
sized fillers which reduced the tendency of filler - matrix of unfilled polypropylene is 22.0 MPa. The figure shows that
interaction from taking place. Thus, the samples can be the hardness of all filled polypropylene at a given filler par-
elongated to a much higher value. However, at the highest ticle size increased with increase in filler content. This result
filler content investigated (40.0 wt. %), the degree of filler indicates enhancement of abrasion and impact strength of the
matrix interactions might have become more prominent even composites. For a reinforcing filler, the composite becomes
in the case of composites of smaller sized filler. Conse- stiffer and harder with increase in filler content. Such in-
quently, dramatic reduction in EB was observed. Secondly, creases in composites hardness with increase in filler content
the interface needs to be considered. The increment in filler have been reported by Chakraborty et al[29], and Igwe and
contents will eventually result in a reduction of the de- Njoku[30]. Generally, the hardness of all the composites
formability of a rigid interface between the fillers, and decreased with increase in the filler particle size at any given
polypropylene matrix. Talc filled polypropylene did not filler content considered. At any given filler particle size
show any elongation at break, an indication of the brittle considered, the order in the enhancement of hardness of
nature of the composites. polypropylene is egg shell > fish bone powder, and when talc
3.1.5. Impact Strength was incorporated into polypropylene, the observed order is
egg shell > fish bone powder > talc.
The data on impact strength of the polypropylene com-
140
posites are illustrated graphically in Figure 5. The figure
shows that the impact strength of polypropylene composites
Rockwell Hardness, MPa

120
increased with increase in filler content at any filler particle
size considered. Such an increase in impact strength of a 100
thermoplastic composite with increase in filler content has
been reported in the literature[23,28]. The impact strength of 80
0.15 µm ESP
the composites was observed to decrease with increase in 0.30 µm ESP
60
filler particle size for any filler content considered. Thus, 0.42 µm ESP
0.15 µm FBP
increasing the particle size of the fillers at a given filler 40 0.30 µm FBP
content probably increased the level of stress concentration 0.42 µm FBP
in the composites with the resultant decrease in impact 20 0.15 µm Talc
strength. However, Guo et al[16] who investigated poly-
propylene/carbonate system found that the impact strength of 0
0 10 20 30 40 50
the composites increased at first with increase in filler con- Weight of Filler ,%
tent, and later, decreased with further addition of fillers.
Figure 6. Plot of Rockwell Hardness versus Weight of Filler for Poly-
50
propylene Composites at different Filler Particle Sizes
45
Impact Strenght, J/m

40 3.2.2. Water Sorption

35 The variation of water absorbed by the composites with
30
0.15 µm ESP
filler content at any given filler particle size is not much.
25 0.30 µm ESP Similarly, the amount of water absorbed by the composites at
20
0.42 µm ESP a given filler content varies slightly with the filler particle
0.15 µm FBP
15 0.30 µm FBP
size. These observations are indications that the amount of
10
0.42 µm FBP water absorbed by polypropylene composites is not strongly
5
0.15 µm Talc
dependent on the filler content or particle size but on the
0
nature of filler used. Figure 7 shows that all the filled poly-
0 10 20 30 40 50 propylene absorbed more water than unfilled polypropylene.
Weight of Filler ,%
Fish bone powder composites of polypropylene were ob-
Figure 5. Plot of Impact strength versus Weight of Filler for Polypropy- served to absorb more water than those of egg shell powder.
lene Composites at different Filler Particle Sizes However, talc filled polypropylene absorbed less water than
Figure 5 shows that when talc is used to make the com- those of egg shell or fish bone powder. Bogoera-Gacera et
posites, the order in enhancing the impact strength of poly- al[31] who studied jute fibre filled polypropylene reported
propylene is fish bone > talc > egg shell powder. However, that the amount of water absorbed by the composites in-
for a given filler particle size, the order is fish bone > egg creased with increase in jute fibre content. Similar observa-
shell powder. tions to ours in this study have also been reported by Ewu-
lonu and Igwe[32] for oil palm fruit bunch fibre filled high
3.2. End-Use Properties density polypropylene.
 Isaac O. Igwe et al.: Studies on Properties of Egg Shell and Fish Bone Powder Filled Polypropylene 60

1.2
3.2.4. Flame Propagation
1 Figure 9 shows that the rate of burning of the composites
Water Sorption ,%

at any given filler particle size decreased with increase in

0.8
filler contents. The burning behavior of polypropylene, a
0.15 µm ESP
0.6 0.30 µm ESP
thermoplast, involves shrinkage and often, melting when
0.42 µm ESP subjected to heat. Both melting and shrinkage have the effect
0.4
0.15 µm FBP
of reducing the apparent flammability of polypropylene. On
0.30 µm FBP
0.42 µm FBP approaching the ignition source, polypropylene shrinks, and
0.2
0.15 µm Talc even, drips away from the flame. This behavior ensures
0
energy removal, decrease in surface area exposed, and hence,
0 10 20 30 40 50 reduction in oxygen accessibility. The present flame retar-
Weight Of Filler , %
dant property of egg shell, and fish bone powder fillers in-
Figure 7. Plot of Water Sorption versus Weight of Filler for Polypropy- vestigated could be attributed also to their calcium carbonate
lene Composites at different Filler Particle Sizes
contents among the other factors.
The level of water absorb by egg shell, and fish bone
powder filled polypropylene is considerably higher than
those for other mineral filled systems[6]. Water absorption is
one of the important characteristics of composites that de-
termine their end use applications. It can lead to a decrease in
some of the composites properties, and therefore, needs to be
considered when selecting applications for possible use of
egg shell, and fish bone powder filled polypropylene.

3.2.3. Specific Gravity

Data on the specific gravity of the various filled poly-
propylene are illustrated graphically in Figure 8. The specific
gravity of unfilled polypropylene is 0.95. Figured 8 shows Figure 9. Plot of Flame Propagation Rate versus Weight of Filler for
that there was a general increase in the specific gravity of Polypropylene Composites at different Filler Particle Sizes
polypropylene composites in comparison to unfilled poly-
propylene at any given filler particle size considered. How- Both fish bone, and egg shell contain calcium carbonate
ever, the specific gravity of the composites decreased with (CaCO3)[30,31]. On the application of heat/flame, calcium
increase in the particle size of the fillers. The increase in the carbonate decomposes according to the equation,
∆
specific gravity with a reduction in the filler particle size CaCO3  → CaO + CO2 (1)
could be attributed to the greater and more uniform disper- With the evolution of carbon dioxide (CO2) which does not
sion of the smaller sized fillers in the polypropylene matrix. support combustion. The more the fillers are incorporated
The general increase in the specific gravity of the prepared into polypropylene, the more the quantity of CaCO3 in the
composites with increase in filler contents as was observed composites, and the less, the tendency of the composites to
in this study is in general agreement with our earlier re- burn since CO2 is a good fire extinguisher. Another possible
ports[19,32]. In this study, egg shell, and fish bone powder factor for the observed flame retardant property of the fillers
have shown greater increase in specific gravity over talc in could be the interaction of the fillers with polypropylene, the
the prepared composites. possible mechanism which has been described previously
1.6 [19].
The effect of filler particle sizes on the flame retardant
Specific Gravity

1.4
property of egg shell, and fish bone powder is not very ap-
1.2
parent in this study since all the filler particle sizes investi-
1 0.15 µm ESP gated exhibited similar flame retardment property.
0.30 µm ESP
0.8 0.42 µm ESP
0.15 µm FBP
0.6 0.30 µm FBP
0.42 µm FBP 4. Conclusions
0.4 0.15 µm Talc
Egg shell, and fish bone powder have been utilized suc-
0.2
cessfully in preparing polypropylene composites. The tensile
0 strength, tensile modulus, flexural strength, impact strength,
0 10 20 30 40 50
Weight of Filler, %
hardness, and specific gravity of the polypropylene com-
Figure 8. Plot of Specific Gravity versus Weight of Filler for Polypro- posites were found to increase with increase in filler contents,
pylene Composites at different Filler Particle Sizes and decrease in filler particle size. The elongation at break of
61 American Journal of Polymer Science 2012, 2(4): 56-61

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