Materials Sciences and Applicatio n, 2011, 2, 785-800
doi: 10.4236/msa.2011.27108 Published Online July 2011 (http://www.SciRP.org/journal/msa)
785
Effects of Synthetic and Processing Methods on
Dispersion Characteristics of Nanoclay in
Polypropylene Polymer Matrix Composites
T. P. Mohan, K. Kanny
Composites Research Group, Department of Mechanical Engineering, Durban University of Technology, Durban, South Africa.
Received February 16th, 2011; received March 21th, 2011; accepted May 6th, 2011.
ABSTRACT
This work presents the effect of synthetic procedures (extrusion and casting) on the dispersion characteristics of nano
layered silicate clay particles in the polypropylene (PP) polymer matrix. Three different molecular weights PP samples
are taken and filled with nanoclay of 1 wt% and 3 wt%, and these nanocomposites were synthesized by using an extru-
sion or casting methods. The X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) is used to charac-
terize the structure and morphology of nanocomposites. Rheological and mechanical results show that the extruded
products are better than that of cast products. The outcome of this work is discussed in this paper.
Keywords: Polymer-Clay Nanocomposites, Nanocomposites, Nanoclays, Polypropylene, Mechanical Properties
1. Introduction
In modern plastics, reinforcement of any inorganic or
organic particles is the most common method to improve
the properties of the polymer. In particular, Polymer Clay
is an interesting and very promising research area due to
cost effective and their ease of availability from natural
resources. Smectic clays, in particular, montmorillonite
(MMT) type of clays are predominantly used as nano
fillers in the Polymer Clay Nanocomposites (PCN).
Naturally available MMT clays are hydrophilic and they
must be made organophilic (hydrophobic) to have com-
patible with most host polymers, because most of poly-
mers are hydrophobic. Organic treatment is typically
accomplished via organic cations, namely onium or qua-
ternary ammonium based salts in MMT clays. When
these organotreated MMT clays are filled in to the host
polymer matrix, two types of morphologies will form,
namely, intercalated and delaminated/exfoliated nano-
composite structure. The intercalated structure is a
well-ordered multilayered structure of silicates, where
the polymer chains are just inserted into the interlayer
spaces (intergallery region). On the other hand, in the
exfoliated/delaminated structure the polymer chains
separate individual silicate layers well apart, e.g., 80 -
100 Å or more, and no longer close enough to interact
with each other. Sometimes in exfoliated structure,
nanolayers are randomly dispersed in matrix polymer.
The aspect ratio (length/thickness) of individual nanola-
yer of clay is very high in the order of several 100 to
1000, and therefore contribute to the improved mechani-
cal properties in polymer system along the loading direc-
tion and as well as serves as an impermeable medium
when the host polymer is exposed to the gas/moisture
medium. The maximum utilization of this aspect ratio is
fully exploited by an exfoliated structure of PCN com-
posites rather than an intercalated structure. Hence,
achieving an exfoliated structure is a real challenge in
this PCN system, even though various polymers are used
in recent years [1-11].
Polypropylene (PP)-clay nanocomposites is an area of
tremendous interest due to wide application of PP poly-
mer in commodity areas and also recent usage in engi-
neering applications. The addition of nanoclay in PP ma-
trix increases the thermal stability, increases physical
properties (dimensional stability), improves flame retar-
dant properties (increased thermal-oxidative stability and
reduced Heat Release Rate), and improves mechanical
properties and fracture properties and gas barrier proper-
ties. PP is a relatively inert thermoplastic polymer with
non polar characteristics and moreover does not have any
reactive functional group. So there cannot be any reac-
tion in PP with alky l ammonium ions of organo MMT

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 786
Matrix Composites
clays in the intergallery regions of clays. Hence, the
nanolayer dispersion in PP matrix can be obtained only
through proper shear device with controlled processing
parameters. Several studies in literature have focused on
addition of compatibilizer in PP and clay nanocomposites,
effect of organoclay types, thermal and mechanical
properties [12-25].
From the literature work of PP-clay nanocomposites it
is found that the report on the influence of molecular
weight and synthetic methods of PP polymer is not fully
exploited. Hence, in this work a detailed insight is given
on how the synthetic methods, processing conditions and
their resultant structure and morphology affects various
molecular weights of PP polymers that are filled with
nanoclay particles. Considering the difficulties in achiev-
ing the exfoliation structure, such studies are important in
PP-clay based nanocomposites because the intercalation
and exfoliation structure takes place only through proper
control of processing parameters as well as the synthetic
methods. In this work, three different molecular weight
of PP sample were chosen and nanoclays were added at 1
wt% and 3 wt% and the materials were developed either
by extrusion or casting methods.
2. Experimental Details
2.1. Materials
Polypropylene pellets (melting point 168°C) were pro-
cured from Chempro, South Africa. Three different mo-
lecular weights (Mw) of PP polymer (Mw of 3.5 × 105,
2.06 × 105 and 1 × 105) were procured from Chempro,
South Africa. Mw of 3.5 × 105 is designated at high mo-
lecular weight polypropylene (LM-PP), Mw of 2.06 × 105
is designated at medium molecular weight polypropylene
(MM-PP) and Mw of 1 × 105 is designated at low mo-
lecular weight polypropylene (LM-PP) in future discus-
sions. Cloisite 15 A nanoclay was obtained from South-
ern Clay Products, USA. This Cloisite 15 A clay is
montmorillonite clay that was organically modified with
a quaternary ammonium salt.
2.2. Nanocomposite Preparation
The PP-clay nanocomposites was prepared by using two
methods, namely, extrusion and casting. In extrusion
method, the polypropylene pellets and the nanoclay were
combined in a REIFFENHAEUSER single screw ex-
truder. The extruder has a 40 mm diameter single rotat-
ing screw with a length/diameter ratio (L/D) of 24 and
driven by a 7.5 kW motor. Extruder has got three heating
zones along the length of the screw as follows: Zone 1
(Hopper or pellet loading end), Zone 2 (centre region of
screw) and Zone 3 (extrusion end). The melt mixing
conditions were kept at constant temperature of 190°C
(Zone 1), 230°C (Zone 2) and 230°C (Zone 3), and the
screw speed is kept at 80 rpm. In casting method, the PP
pellets and nanoclays of desired weight content are
mixed together by mechanical mixer at room temperature
and then heated to its melt temperature using a LABCON
HTR2 environmental heating chamber. After placing in
the molten condition for the desired time (15 minutes),
the molten sample was poured in the aluminium mould
with dimensions of 275 × 175 × 10 mm, and allowed it to
set at room temperature.
2.3. Characterization
The structure of nanocomposites is studied by using
XRD and TEM methods. A Philips PW1050 diffracto-
meter was used to obtain the X–Ray diffraction patterns
using CuKα lines (λ = 1.5406 Å). The diffractrograms
were scanned from 2.5˚ to 12° (2θ) in steps of 0.02˚ us-
ing a scanning rate of 0.5˚/min. Microscopic investiga-
tion of selected nanocomposite specimens at the various
weight compositions were conducted using a Philips
CM120 BioTWIN transmission electron microscope with
a 20 to 120 kV operating voltage. The specimens were
prepared using a LKB/Wallac Type 8801 Ultramicro-
tome with Ultratome III 8802A Control Unit. Ultra thin
transverse sections, approximately 80 - 100 nm in thick-
ness were sliced using a diamond coated blade.
Melt Flow Index is measured for test samples as per
ASTM D1238 testing method. Thermal Analyzer DSC
instrument is carried out for composites series to study
the thermal properties. Heating were carried out from
room temperature to 200°C at the heating rate of
10°C/min and two heating scans have been conducted on
the test specimen. In heat –1 scanning, the melting tem-
peratures (Tm1) were observed. In these curves, ΔH (J/g)
value of melting peak is measured and the % crystallinity
is measured by comparing with the theoretical 100%
crystalline PP melting peak value (115 J/g) [26]. The %
crystallinity is calculated by taking the ratio of ΔH of
melting of test sample to the ΔH of 100% crystalline PP
polymer. Once the polymer is taken to molten state, it is
rapidly cooled to room temperature using liquid nitrogen
and again heat –2 scan is conducted up to 200°C. In heat
–2 scan, crystallization temperature (Tch) and actual
melting point (Tm) of material is measured. In a special
case, once the polymer is taken to molten state (heat –1)
it is slowly cooled at the rate of 10°C/min to measure the
crystallization temperature on cooling (Tcc). Crystalliza-
tion rate is measured in composites series by keeping the
samples at their respective crystallization temperature
(Tch) at different minutes followed by rapid quenching
using cold water to room temperature at the rate of

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer
Matrix Composites
787
100°C/min. The quenched specimen is further heat
scanned using DSC to measure the % crystallinity using
above mentioned formula.
2.4. Mechanical Testing
Tensile tests were performed on virgin PP and the nano-
composite specimens using the LLOYDS Tensile Tester
fitted with a 20 kN load cell. The tensile tests were per-
formed at a crosshead speed of 1 mm/min in accordance
with the ASTM D3039 standard. Five tensile specimens
is taken and the average value is considered for plotting
stress-strain curves. It is envisaged that the standard de-
viation of all the test specimen values are within 3%. The
fracture surfaces of tensile specimens were examined by
using JEOL JSM 840A scanning electron microscope
(SEM).
3. Results and Discussions
3.1. Structure and Properties
Table 1 shows the melt flow behaviour of PP-clay series.
The result shows that the melt viscosity of all the PP
polymer series (LM, MM and HM) is almost constant.
The addition of clay increases the melt viscosity of the
polymer. The rate of increase in viscosity is higher for
HM-PP-clay series than other series. The melting point
of PP series is shown in Figure 1 of DSC heat 1 scan. It
shows that the melting point of PP polymer series are
Table 1. Melt flow index of PP-clay series.
Material MFI, g/10 min
LM-PP 11
LM-PP + 1% clay 10
LM-PP + 3% clay 9
MM-PP 11
MM-PP + 1% clay 9
MM-PP + 3% clay 8
HM-PP 11
HM-PP + 1% clay 7
HM-PP + 3% clay 6
almost constant. However, in heat 2 scanning of DSC
(Figures 2 and 3) result shows that the crystallization
temperature (Tch and Tcc) of LM-PP is higher than that of
other PP series. The effect of nanoclay on the DSC prop-
erties is shown in Table 2. Nanoclay addition increases
the Tch and Tcc temperature of PP series. The rate of in-
crease of crystallization temperature is lesser for HM-PP
series than other PP series. The melting point of PP is by
and large unaffected due to the presence of nanoclay.
The increased crystallization behaviour of PP-clay
nanocomposites is examined by studying the rate of
crystallization formation. Table 3 shows the % crystalli-
zation achieved at various time intervals. It is observed
that the rate of crystallization formation is higher in
nanoclay filled PP composites. Among the nanocompo-
site series, LM-PP series filled with nanoclay shows
higher rate of crystallization formation. As LM-PP
Table 2. DSC heating result of nanocomposites.
Material Tm1 % crystallinity Tch T
m T cc
LM-PP 168 62 114 168 119
LM-PP + 1% clay 169 71 117 169 125
LM-PP + 3% clay 169 74 116 169 127
MM-PP 169 56 112 166 117
MM-PP + 1% clay 170 62 115 168 123
MM-PP + 3% clay 170 64 113 167 125
HM-PP 169 54 112 166 117
HM-PP + 1% clay 170 59 115 167 121
HM-PP + 3% clay 169 61 114 167 122
Table 3. Crystallization behaviour PP-clay series.
LM-PP series MM-PP series HM-PP series
Time, min 0% clay 1% clay 3% clay0% clay1% clay3% clay0% clay 1% clay 3%
clay
0 0 0 0 0 0 0 0 0 0
1 17 24 26 13 16 17 12 14 16
2 36 41 43 30 36 38 28 32 34
3 47 61 66 41 46 47 38 43 45
5 62 71 74 56 62 64 54 59 61

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 788
Matrix Composites
050100150 200 250
Temperature, °C
heat flow (endo down)
LM - P P
MM - PP
HM - PP
Figure 1. DSC heat –1 scan of PP series.
050100 150 200 250
Te m pera ture, °C
Heat flow (endo down)
LM - P P
MM - PP
HM - PP
Figure 2. DSC heat –2 scan of PP series.
haslower molecular weight, the crystal formation is rela-
tively easier than that of higher molecular weight PP
nanoclay composites.
The increased crystallization rate and % crystallinity
of nanoclay filled PP composites suggests that the nano-
clay acts as a nucleating agent. The nucleating behaviour
is further examined by studying the Avarami kinetic
equation. Equation 1 shows the general Avarami equa-
tion as a function of relative crystallinity (Xf) and time to
achieve Xf.

() 1n
r

X
teKt  (1)
where K and n are constants that are considered as the
important parameters for crystallization mechanisms.

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 789
Matrix Composites
050100 150200 250
Temperature, °C
Heat flow (endo up)
LM - PP
MM - PP
HM - P P
Figure 3. DSC cooling curves of PP series.
The values of K and n can be calculated by plotting
log[–ln(1 – Xr)] vs. log(t). n and log(K) values are the
slope and intercept values respectively of the Avarami’s
plot. The Avarami plot for PP series and LM-PP-nano-
clayseries is showed in Figures 4 and 5 respectively. The
Avarami’s kinetic constants, namely, n and K values are
shown in Table 4. The remarkable increase in kinetic
constant (K) and crystallization rate; decreased n value
suggests that the nanoclay acts as the nucleating agent in
the system and hence increase the % crystallinity and
rate.
Further, this rheological effect of nanoclay on struc-
ture and morphology is planned to examine for PP poly-
mer. Hence, the structure and morphology of extruded
samples is examined by using XRD and TEM methods.
Figure 6 shows the XRD patterns of PP-clay series.
Nanoclay (Cloisite 15A) shows the diffraction peak of 2θ
at 3.3° and corresponds to interlayer spacing of nanoclay
(d-spacing) of 26.75 Å (calculated from Bragg’s diffrac-
tion law of 2d Sinθ = nλ). HM-PP + 3 wt% clay shows
the diffraction peak at of 2θ at 3.10° and corresponds to
interlayer spacing of nanoclay (d-spacing) of 28.47 Å.
This suggests that the interlayer spacing of nanoclay is
increased by about 1.72 Å due to the presence of matrix
polymer in the interlayer region of nanoclay. The pres-
ence of matrix polymer in the interlayer regions increases
the interlayer spacing of the nanoclays and more over the
results further shows that the nanolayers are arranged
parallel to each other which is a typical intercalated
structure. In MM-PP – 3 wt% nanoclay, the diffraction
Table 4. Avarami’s kinetic constants of PP-clay series.
Material n k
LM-PP 1.02 0.15
LM-PP + 1% clay 0.97 0.26
LM-PP + 3% clay 0.97 0.29
MM-PP 1.10 0.08
MM-PP + 1% clay 1.06 0.14
MM-PP + 3% clay 1.05 0.16
HM-PP 1.12 0.06
HM-PP + 1% clay 1.10 0.10
HM-PP + 3% clay 1.05 0.13
peak occurs at 2θ of 2.98° and this corresponds to the in-
terlayer spacing of clay of 29.62 Å. The result shows that
in MM-PP-3 wt% clay composites, the structure is an in-
tercalated structure with increased interlayer spacing of
nanolayers than that of HM-PP – 3 wt% clay composites.
In the case of LM-PP – 3 wt% nanocomposite, no diffrac-
tion peak is observed and this suggests that the nanolayers
of clay could have randomly dispersed in the matrix
polymer or the clay nanolayers are separated well apart (>
80 Å) so that Bragg diffraction cannot occur due to CuK
lines. This type of structure is called an exfoliated structure
or ordered exfoliated structure. The results further shows
that the low molecular weight based PP-clay composites
form an exfoliated structure and whereas higher molecular
weight based PP-clay composites form an intercalated
structure. To further understand the dispersion of clay in
the polymer matrix, TEM is taken for these composites
are taken and shown in Figure 7. Figure 7 is the bright
field TEM pictures of nanoclay.

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 790
Matrix Composites
-1
-0.9
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
00.1 0.2 0.3 0.40.5 0.6 0.7 0.8
Log (T)
log [-ln(1-Xf)]
LM - PP
MM - PP
HM - PP
Figure 4. Avarami plot of PP series.
-0.8
-0.7
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
0. 1
0. 2
00.2 0.4 0.60.8
log (T)
log [- ln (1- Xf) ]
LM - PP
LM - PP + 1% clay
LM - PP + 3% clay
Figure 5. Avarami plot of LM-PP with clay series.
filled PP composites, in which the bright phase in the
TEM picture is the matrix phase and the dark phase is the
particle phase. LM-PP + 3 wt% nanoclay composites
shows the a well separated distribution nanolayers in the
matrix and such structure is the exfoliated structure.
MM-PP + 3 wt% clay and HM-PP + 3 wt% clay com-
posites shows the parallel arrangement of nanolayers in
the polymer matrix and such structure is called an inter-
calated structure. Further more, the TEM pictures sup-
ports the XRD data of nanocomposite structure. The pos-

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 791
Matrix Composites
036912
2 theta
Intensity (arbitrary unit)
(a)
(b)
(c)
(d)
(e)
Figure 6. XRD pattern of (a) organoclay, (b) HM-PP + 3 wt% clay, (c) MM-PP + 3 wt% clay, (d) MM-PP + 1 wt% clay and (e)
LM-PP + 3 wt% clay.
(a)
(b)

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer
Matrix Composites
792
(c)
Figure 7. TEM of (a) LM-PP + 3 wt% clay, (b) MM- PP + 3 wt% cl a y, (c) HM-PP + 3 wt% clay.
sible reason for intercalated structure in HM-PP and
MM-PP series could be due to the high viscosity of
polymer and clay mixture that could have induced low
shear force during processing. Moreover, all the PP-clay
series are processed at same shear force and this force
might be lesser to exfoliate the clays in higher molecular
weight PP composites.
The effect of this reheological, structure and mor-
phology of nanoclay filled PP composites is further ex-
amined by studying the tensile properties of the compos-
ites. Figure 8 shows the tensile stress-strain curves of PP
series. The curves show that the behaviour of PP series
under loading is different from each other. HM-PP shows
increased failure strain than that of other PP series,
whereas it shows lowest modulus than other PP series.
Table 5 and Figure 9 show the effect of nanoclay on
tensile properties of various PP series. This result shows
that the addition of nanoclay in PP improves the tensile
modulus, strength and failure strain in all the PP series.
The increased modulus in nanocomposites is due to the
molecular level distribution of the clays in the polymer
matrix. The nanoclay increases the molecular strength
due to the nanolevel distribution of the particles and
thereby increases the modulus under loading condition.
The possible increase in the strength of the nanocompo-
sites is due to the nanoclay particles acts as a crack stop-
pers or initiates the crack growth at higher loading level.
In addition to these factors, the extended deformation
mechanisms could have also caused the composites to
fail at higher strength level. To further understand this
deformation mechanisms, SEM of the composites speci-
mens were taken and shown in Figure 10. The fracture
surface of LM-PP is smooth and the crack has propa-
gated in the material with several branched marks caused
due to the propagation of crack front. On the other hand,
fracture surface of LM-PP + 3 wt% clay shows the dif-
ferent fracture morphology. The crack surface shows the
extended deformations (shown in circles) that caused the
material to fail in higher strain level. Also, the crack sur-
face shows the failure occurs under the cavitation
mechanisms (represented by arrows). In this cavitation
mechanism, the propagating crack surrounds the particle
front and will propagate further at higher loading level
until material fails. Hence, these factors have caused the
increased tensile properties of nanoclay filled PP poly-
mer composites. On observing Table 5, it further shows
that the rate of improvement in tensile properties of high
molecular weight PP-clay composite series (MM-PP and
HM-PP) is slower than that of other series. The possible
cause of this could be the formation of intercalated
structure in these nanocomposites. When compared to
intercalated structure, exfoliated structure provides better
improvement in properties due to the random distribution
of nanolayers of clays as well individual dispersion of
nanolayers of clays. In the intercalated structure, group
of nanolayers forms a stacking sequence and orient in
particular direction and this reduces the dispersion ability
of individual nanolayers and also reduces the net aspect
ratio of the nanolayers (length/thickness). Therefore,
better improvement in properties can be obtained in in-
tercalated structure if the nanolayers are dispersed ran-
domly or forms into an exfoliated structure. Hence, to
obtain the better dispersion of intercalated structures, the
processing parameters were varied and examined.

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 793
Matrix Composites
3.2. Effect of Processing Parameters on
Structure and Properties of Nanocomposites
In order to improve the dispersion quality of the
nanolayers of clays particles in high molecular weight PP
polymer matrix (MM and HM series), it is decided to
change the processing parameters. Two parameters were
varied in the extrusion processing, namely, increased
temperature and increased melt shear force. In the first
0
5
10
15
20
25
30
35
40
050100150 200 250 300
strain,%
stress, MPa
LM‐PP
MM‐PP
HM‐PP
Figure 8. Tensile stress-strain curves of PP series.
0.5
1
1.5
2
2.5
012
cl ay co n ten t, wt.%
Tensil e modul us, G Pa
3
LM seri es
MM s eries
HM seri es
(a)

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 794
Matrix Composites
20
25
30
35
40
45
0123
cla y content, w t.%
Tensil e strength, M Pa
LM s eri es
MM series
HM seri e s
(b)
100
120
140
160
180
200
220
240
260
280
300
0123
cl ay co n ten t, wt. %
E lo n g ati o n at break, %
LM series
MM series
HM se ri e s
Figure 9. Effect of nanoclay on (a) tensile modulus, (b) tensile strength and (c) elongation at break of PP series.
Table 5. Tensile properties of PP-clay series.
Modulus Strength Elongation
Material GPa MPa %
LM-PP 1.1 29 130
LM-PP + 1% clay 1.8 33 146
LM-PP + 3% clay 2.3 36 163
MM-PP 1 31 200
MM-PP + 1% clay 1.35 36 233
MM-PP + 3% clay 1.7 38 255
HM-PP 1.1 35 270
HM-PP + 1% clay 1.3 43 276
HM-PP + 3% clay 1.7 49 281

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer
Matrix Composites
795
(a)
(b)
Figure 10. SEM of fracture surface of (a) LM-PP and (b) LM-PP + 3 wt% nanoclay.
case, the extrusion processing temperature is varied from
230°C to 245°C and the resultant change in the XRD
pattern over previous method is shown in Figure 11.
Figure 11 shows the XRD pattern of MM-PP and
HM-PP polymer filled each with 3 wt% clay. The figure
shows a diffraction peak at 2θ of 2.92° and 2.82° and
corresponds to the interlayer spacing of 28.47 Å and
29.62 Å for MM-PP + 3 wt% clay and HM-PP + 3 wt%
clay composites respectively. The results show that the
formation of intercalated nanocomposite structure with
improved d-spacing over the previous processing method
conditions (230°C). In the another case of processing, the
shear force is increased by changing screw rpm from 80
rpm to 120 rpm and keeping the processing temperature
constant at 230°C. Figure 12 shows the XRD pattern of
MM-PP and HM-PP polymers filled each with 3 wt%
nanoclay that were processed by high shear force. The
XRD pattern shows the absence of any diffraction peaks.
This suggests that the structure is an exfoliated structure.
To further under stand the dispersion level of nanoclays
in the polymer matrix, TEM of these processed samples
were taken and shown in Figure 13. Figure 13 is the
TEM of HM-PP + 3 wt% nanoclay processed at two dif-
ferent conditions. It is observed that higher processed

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 796
Matrix Composites
0246810
2 theta
Intensity (arb. unit)
12
Figure 11. XRD of (a) MM-PP + 3 wt% and (b) HM-PP + 3 wt% clay processed at 245°C.
0246810
2 theta
Intensity (arbitrary unit)
12
Figure 12. XRD of (a) MM-PP and (b) HM-PP with 3 wt% clay processed at 120 rpm/230°C.
temperature of composites shows the intercalated struc-
ture and whereas higher shear induced force composites
shows the exfoliated structure. These pictures further
support the XRD result. In high temperature processing,
the separation of nanolayers can occurs only though the
diffusion mechanisms, and the higher molecular weight
polymer might face considerable difficulties in diffusing
into the inter gallery regions of nanoclays and hence re-
sulted in an intercalated structure. Whereas in high shear
force induced nanocomposites processing, the increased
shear force is sufficiently high enough to break the parti-
cles into smaller size, or to delaminate the clay nanolay-
ers. Therefore high shear force can favour the formation
of an exfoliated structure in high molecular weight
polymer composites. The resultant tensile properties due
to these processing effects is shown in Table 6 (Case 1 is

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 797
Matrix Composites
(a)
(b)
Figure 13. TEM of HM-PP + 3 wt% clay processed at (a) 245°C/80 rpm and (b) 230°C/120 rpm.
Table 6. Effect of proc essing parameters on tensile properties.
Modulus, GPa Strength, MPa Elongation, %
Material Case 1 Case 2 Case 1 Case 2 Case 1 Case 2
MM-PP + 1% clay 1.56 1.61 39 44 241 256
MM-PP + 3% clay 1.90 1.97 41 47 261 270
HM-PP + 1% clay 1.38 1.44 48 51 287 301
HM-PP + 3% clay 1.82 1.93 49 56 293 306
high processing temperature and Case 2 is high shear
force). The result shows improved property enhancement
of composites in high shear force condition due to the
formation of an exfoliated nanocomposite structure.
3.3. Effect of Synthetic Methods on Structure
and Properties of Nanocomposites
In a special case, the effect of synthetic methods on the

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 798
Matrix Composites
properties is studied. Here, two synthetic methods are
compared, namely extrusion process and casting process.
Table 7 shows the effect of synthetic methods on tensile
properties of composites. It shows that the extrusion
method shows improved properties than that of casting
method. The possible reason for low property in the
casting method is examined by studying the morphology
of the clay particles in PP matrix using TEM. Figure 14
shows the TEM of 3 wt% nanoclay dispersion in LM-PP
matrix and shows the existence of intercalated nano-
composites structure with agglomerated clay particles.
This agglomerated structure could have caused low
property in the composites. This effect is caused due to
the less shear force during mixing of clay particles and
molten polymer.
4. Conclusions
A relatively new class of material consisting of polypro-
pylene as matrix material and the nanoclay as reinforce-
ment filler is prepared by using extrusion or casting
methods. The result shows that the addition of nanoclays
increases the melt viscosity of the all the type of PP sam-
ples. Nanoclay acts as nucleating agent in LM-PP com-
posites due to the increase of % crystallization and rate
of crystallinity of LM-PP samples. These nucleating ef-
fects of nanoclays in PP samples were studied using
Avarami’s equation. The kinetic study shows reduced
nucleating effect of nanoclays in higher molecular weight
PP samples. Exfoliated structure forms in LM-PP com-
posite series, and where as proper improvement of shear
force in extrusion proved exfoliated structure in higher
molecular weight PP composite series. The low shear
force and agglomeration of particles causes reduced ten-
sile properties of melt cast samples over extruded com-
posite.
The outcome of this work suggests that the nanoclays
acts as a viable nanofiller in the development of particle
filled polymer composites. The nanoclay distribution in
matrix is depended on molecular weight of the polymer,
processing or synthetic conditions. The nanoclays im-
Table 7. Effect of synthetic methods on tensile properties.
Modulus, GPa Strength, MPa Elongation
Material Extrusion Casting Extrusion Casting Extrusion Casting
LM-PP + 1% clay 1.80 1.62 33 31 146 141
LM-PP + 3% clay 2.30 2.18 36 33 163 156
MM-PP + 1% clay 1.61 1.43 44 41 256 239
MM-PP + 3% clay 1.97 1.72 47 45 270 256
HM-PP + 1% clay 1.44 1.21 51 49 301 287
HM-PP + 3% clay 1.93 1.73 56 51 306 293
Figure 14. TEM of melt cast LM-PP + 3 wt% nanoclay.

Effects of Synthetic and Processing Methods on Dispersion Characteristics of Nanoclay in Polypropylene Polymer 799
Matrix Composites
proves the crystallization rate and there by useful for
molding engineering components that require higher
crystallization rate during processing.
5. Acknowledgements
Authors gratefully acknowledges the financial support
provided by National Research Foundation-NRF (Grant
No: 71599) of South Africa for carrying out this work.
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