S. ÇELÝK ERBAª et al.:FABRICATION AND CHARACTERIZATION OF NANOCLAY-REINFORCED THERMOPLASTIC ...
87–94
FABRICATION AND CHARACTERIZATION OF
NANOCLAY-REINFORCED THERMOPLASTIC COMPOSITE
FILMS
IZDELAVA IN KARAKTERIZACIJA NANOGLINE, OJA^ANE
S TERMOPLASTI^NIMI KOMPOZITNIMI FILMI
Seçil Çelýk Erbaº, Suat Bahar Baºtürk
Department of Metallurgy and Materials Engineering, Faculty of Engineering, Manisa Celal Bayar University, Muradiye,
Manisa, 45040, Turkey
Prejem rokopisa – received: 2018-04-25; sprejem za objavo – accepted for publication: 2018-10-12
doi:10.17222/mit.2018.086
A number of nanoclay/poly(methyl methacrylate) (PMMA) composite films were prepared with three different clay
concentrations (0.5 %,1%and2%( w/%)) via a solution-casting process. The nanoclay was modified by applying different
compatibilization techniques: mere silane surface treatment and surfactant application with the addition of a silane agent. The
interlayer distances of the clay galleries were determined using X-ray diffraction (XRD) and the modifications were verified
with Fourier-transform infrared spectroscopy (FTIR) analysis. The dynamic mechanical analyses (DMA) were performed to
clarify the viscoelastic properties of the produced films. Morphological characterizations were carried out with a scanning
electron microscope (SEM). The neat clay/PMMA composites and pure PMMA film were also used to compare the effects of
the compatibilization methods. The silane-modified clay/PMMA composites exhibited the best performance, as compared to
neat PMMA, by considering the storage modulus (17.7 % increase) and the glass-transition temperature (20 % increase).
However, in terms of the dynamic mechanical properties, the joint implementation of these two modification techniques did not
satisfy the expectations, probably due to the excess modifier and the plasticizing effect.
Keywords: nanocomposites, chemical modification, viscoelastic properties, polymer film
Avtorji so s tako imenovanim raztopno-ulivnim procesom pripravili {tevilne kompozitne filme (tanke prevleke) na osnovi
nanogline/polimetil metakrilata (PMMA) s tremi razli~nimi koncentracijami gline (0,5, 1 in 2 masnih dele`ev). Nanoglino so
modificirali z razli~nimi kompatibilizacijskimi tehnikami: s povr{insko obdelavo s silanom (SiH4) ter z aplikacijo povr{insko
aktivne snovi z dodatkom za tvorbo silana. Razdalje med galerijami plasti gline so dolo~ili z rentgensko difrakcijo (XRD) in
modifikacije so verificirali z infrarde~o spektroskopijo s Fourierjevo transformacijo (FTIR). Dinami~ne mehanske analize
(DMA) so izvedli, da bi razjasnili viskoelasti~ne lastnosti izdelanih filmov. Morfolo{ke lastnosti filmov pa so okarakterizirali z
vrsti~nim elektronskim mikroskopom (SEM). Med seboj so primerjali izdelane kompozite glina/PMMA in ~isti PMMA ter s
tem ugotavljali u~inkovitost kompatibilizacijskih metod. S silanom modificirani kompoziti glina/PMMA ka`ejo bolj{e lastnosti
v primerjavi s ~istim PMMA; meritev modula shranjene energije je pokazala 17,7 % izbolj{anje in temperatura prehoda v
steklasto stanje se je povi{ala za 20 %. Vendar pa implementacija obeh tehnik modifikacije z vidika dinami~nih lastnosti ni
izpolnila pri~akovanj, verjetno zaradi prebitka modifikatorja in u~inka plastificiranja.
Klju~ne besede: nanokompoziti, kemijska modifikacija, viskoelasti~ne lastnosti, polimerni film
1 INTRODUCTION
The addition of nanofillers to a polymer medium
results in the formation of polymer nanocomposites that
exhibit significantly improved mechanical, thermal and
physical properties. In composite materials, the rein-
forcing components with a macroscopic size always
include defects. The idea behind the use of nanoparticles
in composites is based on their minimal sizes, small
imperfections and high aspect ratios, which provide a
larger interfacial area that leads to remarkable features,
as compared to neat polymer. Since the discovery of
nanoclay/nylon-6 nanostructures by the Toyota research
group, many researchers have revealed the unique con-
tributions of nanoclay-based hybrids in various appli-
cations, such as automotive, aerospace, coating,
packaging and electronics.
1,2
Although silica, alumina, carbon nanotubes and
graphene are widely employed in nanocomposite appli-
cations, the effects of nanoclays in composites have also
attracted considerable attention due to their high surface
area, low cost and ease of availability. The nanoclay
minerals that show a hydrated alumina-silicate layer
structure can be categorized depending on their formula,
chemical structure and physical properties. Mont-
morillonite (MMT) is the most popular type of nanoclay
and integrated with many plastics using a variety of
techniques.
3
Based on the literature, four main pro-
duction techniques are available for the preparation of
nanoclay-based composites: solution intercalation,
in-situ intercalative polymerization, melt intercalation
and in-situ direct synthesis.
4
The dispersion level of clay
platelets in the polymer matrix is extremely important
Materiali in tehnologije / Materials and technology 53 (2019) 1, 87–94 87
UDK 620.1:620.3:544.236.4 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 53(1)87(2019)
*Corresponding author e-mail:
secil.celik@cbu.edu.tr

for a strong interaction between the platelets. Phase
separated, intercalated or exfoliated structures are the
main morphological types observed in the literature.
5
Generally, the clay minerals show a hydrophilic char-
acter, while the polymers have a hydrophobic behaviour.
In order to eliminate these drawbacks, modification of
the clay is performed to provide compatibility with the
plastic matrix.
6
Organic cations such as an ammonium
ion or phosphonium ions are commonly known organic
modifiers for clay minerals.
The organophilic modification process includes the
exchange of interlayer inorganic cations with organic
amonium salts, which leads to a widening of the inter-
layer distance. Thus, the basal spacing (d) extends and
the diffusion of polymer into the clay galleries becomes
possible.
7
Chen and Yoon revealed the effects of the silanization
process on the exfoliation degree of various nanoclay-
based composites. They concluded that the treatment of
different organically modified clay minerals with glyci-
dyloxypropyltrimethoxysilane increased the hydropho-
bicity of clay.
8
Ianchis et al. performed similar research
and they compared the influences of four alkoxysilanes.
Based on their findings, the glass-transition temperatures
(T
g
) of the nanostructures were significantly affected by
the modification of clay with various silane coupling
agents.
9
Unnikrishnan et al. concentrated on the thermal,
mechanical and flammability properties of Cloisite-type
nanoclay/PMMA composites. Based on their study, the
addition of nanoparticles resulted in an increase of the
basal spacing, which is an indication of intercalation
and/or exfoliation.
The incorporation of maleicanhydride (MA) led to an
increase of the thermal stability and T
g
.
10
Salahuddin
studied the effect of an organoclay addition on the
mechanical properties of PMMA-based composites.
Independent of the filler concentration, both the hardness
and Izod impact strength values increased, while the
tensile properties were enhanced only for a certain clay
content.
11
Vasiliu and her co-workers investigated the optical
transparency characteristics of PMMA/MMT films.
According to their results, the layered silicate/PMMA
films had an optical transmission of greater than 80 % in
the visible-light region.
12
Karesoja et al. reported the
dynamic mechanical (DMA) properties of MMT/Poly
(BuA-co-MMA) nanocomposite films. In their study, the
clay content increase did not significantly affect the
storage and loss modulus of composite films, as well as
T
g
.
13
Kumar et al. noticed the rheological, flammability
and dynamic mechanical (DMA) features of PMMA-
based nanocomposites with/without a compatibilizer. It
was observed that the compatibilizer promoted the
interfacial bonding, which led to an increase in T
g
as well
as optical clarity and flammability.
14
In the study of
Huang and Brittain, the MMT/PMMA nanocomposite
structures exhibited considerable improvements in both
T
g
and decomposition temperatures.
15
Deng et al. used a
new initiator potassium diperiodatocuprate (Cu
3+
) and
according to their experimental results, the (Cu
3+
) exhib-
ited a significant role in the integration and intercalation
of PMMA chains into OMMT layers.
16
Khajehpour et al.
focused on the thermal and morphological properties of
silane-modified montmorillonite (Mnt) based fluoro-
elastomer (FKM) composites. Based on the XRD results,
an approximately 169 % increase in the basal spacing
was found with reasonably good dispersion.
17
The main motivation of this study is the application
of an organophilic modification and silane surface treat-
ment to the same composite films to combine their
synergetic effects. Thus, two modification methods
(silane agent treatment or silane agent+surfactant appli-
cation joint modification) with three different clay
concentrations (0.5, 1 and 2) % were studied. After the
modification process, the nanoclay and host PMMA
were integrated with a conventional solution-casting
method. During the work, the effects of the amount of
nanoclay on the dynamic mechanical properties of the
composite samples were investigated, as well as their
dispersion characteristics. The resulting properties of
both the pure PMMA and the produced nanocomposite
films were evaluated by considering the FTIR, XRD,
DMA and SEM techniques.
2 EXPERIMENTAL PART
2.1. Materials
The polymethylmethacrylate (PMMA), tetrahydro-
furane (THF), cetyltrimethylammonium bromide (surfac-
tant) and bentonite nanoclay were purchased from
Merck™. The 3-glycidyloxypropyltrimethoxysilane
agent for the modification of the powder phase was
supplied by Dow Corning™.
2.2. Modification of nanoclay powder
In this study, two modification strategies were carried
out for the nanoclay powders. In the first process,4gof
nanoclay was added to an ethanol (380 mL) and water
(20 mL) mixture for 30 min to allow the hydrolysis
reaction. After that,4go f3-glycidyloxypropyltri-
methoxysilane was added to this mixture dropwise. The
mixing speed was then maintained for 30 min in a
homogenizer at 12,000 min
–1
and for 15 min in a probe,
ultrasonically tuned to 80 % amplitude. The mixture was
filtered and washed with ethanol, and then dried in an
ovenat80°C.
18
Bentonite clay was modified by using cetyltrime-
thylammonium bromide as an intercalating agent
(Figure 1). For this purpose, 1 g of nanoclay was added
to a 100-mL methanol (90 x/%) and water (10 x/%)
mixture and stirred at 70 °C until all the clay particles
dispersed in the solvent. Unlike the first process,1gof
surfactant (cetyltrimethylammonium bromide) was
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88 Materiali in tehnologije / Materials and technology 53 (2019) 1, 87–94

added to this mixture and stirred for 1 h. 1g of 3-glycidy-
loxypropyltrimethoxysilane was introduced dropwise
and the mixture was blended for4hatthesame tem-
perature. The final mixture was filtered and washed with
methanol, and then dried in an oven at 80 °C.
17
2.3. Production of PMMA/nanoclay composites
Both the neat PMMA and PMMA/nanoclay compo-
site films were prepared using the solution-casting
technique. During the pure polymer film production, 2 g
of PMMA and 40 mL of THF were mixed and stirred at
90 °C for 10 min. After the dissolution of all the PMMA,
the mixture was poured into a clean petri dish. Following
the solvent’s evaporation in an oven at 70 °C, the
produced PMMA film was stripped out from the petri
dish.
A similar treatment was also carried out for the com-
posite specimen’s preparation. Modified or unmodified
clay powders with three different weight percentages
(0.5 %,1%a n d2% )w e r ea d d e dt ot h ep r e p a r e d
PMMA solution according to the above procedure. After
stirring for a while with the magnetic stirrer, the
mixtures were poured into the petri dish. The petri dish
was sonicated for a while to provide a homogeneous
distribution of the clay particles. The PMMA/nanoclay
composite film was obtained after the evaporation of the
mixture in the oven.
2.4. Characterization
The Fourier transform infrared spectrum (FTIR) anal-
yses were performed with an Agilent™ Technol-
ogies/Cary 660 FTIR spectrophotometer to confirm the
different functional peaks in the nanocomposites. The
X-ray diffraction (XRD) profiles were measured with a
Panalytical Empyrean™ with Cu–K
 radiation ( =
0.15406 nm) and the patterns were recorded for the 2 range 1°–10° with a 0.01 s
–1
scan speed. The basal
spacings of the modified and neat clay powders were
estimated from the d (001) peaks in the XRD pattern.
The DMA characteristics of the film specimens were
assessed with TA™ Instrument Q800 equipment. The
rectangular test specimens were deformed via the dual
cantilever mode from 40 °C to 150 °C with a heating rate
of 5 °C/min under a liquid-nitrogen flow. The storage
modulus (E'), loss modulus (E") and loss tangent (tan  )
of each sample were recorded at a frequency of 1 Hz.
Morphological studies of the nanocomposite films were
carried out with a COXEM™ EM-30 Plus scanning
electron microscope (SEM).
3 RESULTS AND DISCUSSION
3.1 Characterization of the Modification Effects
In order to reveal the effects of the silane surface
modification and the surfactant application, the FTIR
spectra of the original neat nanoclay, silanized nanoclay
and surfactant-silanized nanoclay powders were recorded
in the range 4000–400 cm
–1
and shown in Figure 2.
S. ÇELÝK ERBAª et al.:FABRICATION AND CHARACTERIZATION OF NANOCLAY-REINFORCED THERMOPLASTIC ...
Materiali in tehnologije / Materials and technology 53 (2019) 1, 87–94 89
Figure 2: FTIR spectra of: a) neat nanoclay, b) silanized nanoclay and
c) surfactant-silanized nanoclay
Figure 1: Bentonite intercalation with cetyltrimethylammonium
bromide

There are some characteristic bands that can be seen
in all the spectra (Figure 2, a), b) and c)) at approxim-
ately 3300 cm
–1
and 3600 cm
–1
. These peaks can be des-
cribed as Al-OH, Si-OH bond-stretching vibrations
(peaks found in silanized and pure clay) and stretch-
ing-bending vibrations of the water (H
2
O) between the
clay layers. A pair of strong bands, 2856 cm
–1
and 2929
cm
–1
, were observed on modified bentonite, which could
be assigned to the symmetric and asymmetric stretching
vibrations of the methylene group ( CH
2
). Furthermore,
their bending vibrations between 1486 cm
–1
and 1470
cm
–1
that supported the intercalation of surfactant
molecules between the silica layers was not observed in
the neat clay.
The X-ray profiles of the materials provide con-
siderable information about their dispersion grades.
Based on the literature, the bentonite nanoclay generally
exhibited its characteristic peak(s) between 1° and
10°;
19,20
therefore, during the study this range was
generally taken into account in terms of the XRD
interpretation. The analysis results of the pure clay,
silanized clay and surfactant-silanized clay are shown in
Figure 3. Depending on these spectra, the unmodified
nanoclay exhibited a characteristic peak at 5.984° with a
d-spacing of 1.4981 nm. As seen in the same figure, the
merely silane surface modification slightly reduced the
2 value to 5.757° when the interlayer spacing increased
to 1.5337 nm. In addition to that the peak showed a
lower intensity and broadening character that can be the
attributed to the intercalation of the clay platelets. In the
XRD graph of the surfactant-silanized nanopowder, an
interesting hump appeared at a 2 angle that is equiva-
lent to 0.3993 nm. A few researchers encountered this
kind of profile in the literature and they considered the
hump as an indication of an amorphous phase.
21
Thus, it
can be concluded that the surfactant and silane agent
application resulted in the existence/increase of amor-
phous content.
3.2. Dynamic mechanical properties of nanocomposi-
tes
The viscoelastic properties of the films produced
using the solution-casting technique were determined
with DMA to clearly compare the effects of the nanoclay
addition under cycling stress at various temperatures. In
Figure 4, both the storage modulus (E’) and the damping
(tan  ) parameters are plotted as a function of the
temperature. Although the data were recorded between
40 °C and 150 °C, the temperature axis ends at 120 °C to
clearly identify the results of the parameters. In these
graphs, the modification types were compared by con-
sidering the same nanoclay percentage.
It is evident that the major differences in the pre-
paration procedure for the nanoclay-based composites as
well as extensive variations of nanoclay type (mass,
platelet size, aspect ratio, homogeneous distribution,
etc.) can result in differences in the mechanical pro-
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90 Materiali in tehnologije / Materials and technology 53 (2019) 1, 87–94
Figure 4: Storage modulus and tan delta plots containing neat PMMA
and a) 0.5 % nanoclay/PMMA composite, b) 1 % nanoclay/ PMMA
composite, c) 2 % nanoclay/PMMA composite
Figure 3: XRD spectra of pure nanoclay, silanized nanoclay and sur-
factant-silanized nanoclay

perties. Therefore, in this work, the individual influence
of the modification method and the clay amount are
considered to accurately describe the DMA properties.
As seen in Figure 4a to 4c, the storage modulus (E’)
decreases as the temperature increases. It is observed that
above 55–60 °C, the decline of E’is more significant for
all of the samples and tan  starts to rise due to the onset
of a transition from the glassy state to the rubbery state.
The measured modulus values of neat PMMA and the
composite films are tabulated in Table 1. It is concluded
from the table that the E’ parameter shows unstable
changes depending on the modification technique. The
joint effects of the silane treatment and the surfactant
application did not satisfy the expectations in terms of
E’. This may be explained by the adverse influence of
the double modification, which probably decreased the
capability of PMMA to penetrate the clay platelet spac-
ings and caused the stiffness reduction of the composites.
It might also be the fact that some of the excess modifier
migrated from the nanoclay to the polymer, led to a
negative plasticizing effect and resulted in the lower
dynamic mechanical properties.
22,23
The existence of the
amorphous phase, which reduces the rigidity of
materials, in the surfactant-silanized clay powder can be
another possible reason for the lower E’values.
Table 1: Glass-transition temperatures (T
g
) and storage moduli (E’)of
neat and composite films based on dynamic mechanical analyses.
Amount of
clay (w/%)
Sample
T
g
(°C)
E’@ 40
°C (MPa)
0 Neat PMMA 80.6 1871.57
0.5
Neat clay/PMMA comp. 78.81 2192.34
Silanized clay/PMMA
comp.
94.98 2201.98
Surfactant-silanized
clay/PMMA comp.
90.45 1575.20
1
Neat clay/PMMA comp. 83.91 1527.64
Silanized clay/PMMA
comp.
95.17 2141.78
Surfactant-silanized
clay/PMMA comp.
93.20 1592.01
2
Neat clay/PMMA comp. 90.86 2193.66
Silanized clay/PMMA
comp.
96.68 1017.21
Surfactant-silanized
clay/PMMA comp.
95.76 1188.14
The silanized films usually exhibited higher modulus
values, except for the 2 % (w/%) sample, as compared to
the neat PMMA and other composite types. The treat-
ment of nanoclay with silane leads to a reaction between
the alkoxysilane Si-O-R functionalities with hydroxyl
groups on the edges of the clay and promotes the Si-O-Si
bridges by removing alcohols (R-OH).
17,24
Therefore, the
maximum E’ values are attributed to the strong bonding
formed between the host polymer and the silanized
nanoclay.
The stiffnesses of the neat clay/PMMA composites
were also investigated and it is surprising that the storage
moduli of the films (0.5 % and 2 %) are relatively good.
The E’ values of these films are close to the silanized
samples and this situation might be due to the high
aspect ratio of the filler and the relatively good disper-
sibility.
Generally, the mutual effect between the polymer
chains and the nanoparticle surface promotes the gene-
ration of the polymer nanolayer close to the nanoparticle
surface that determines the glass-transition temperature
(T
g
).
25
Therefore, the vigorous interaction established
between the composite components results in the
improvement of this parameter. In terms of the damping
characteristics of composite films, the T
g
values of all the
samples were measured as the peak value of a tan
 -temperature plot. The single tan  peak’s existence
indicates the pure amorphous structure of the polymer
nanocomposites, as seen in Figure 4a to 4c. Almost all
the curves in this figure shifted towards the higher tran-
sition temperature, compared with the pure polymer due
to the restricted polymer chain motion at the clay-poly-
mer interface. As it is well known that if the T
g
value of
the interphase is below than matrix the prepared com-
posite possesses a lower glass-transition temperature. In
the opposite situation, the composite shows a higher T
g
.
26
In this study, whole nanocomposites independent of
modification type (except 0.5 % neat nanoclay/PMMA
sample) exhibit a higher T
g
, which can be attributed to
the strong link between the PMMA and the nanoclay in
the interphase region. The 0.5 % wt. neat nanoclay/
PMMA shows a lower T
g
as compared to the neat
PMMA, which is probably due to the smaller interfacial
interaction of the components throughout the interphase
zone. The increase of the clay content also considerably
enhances the glass-transition temperatures of the
composite films, as seen in Table 1. These results clearly
showed that the introduction of more nanoclay promotes
the adhesion of the polymer and layered silicate, which
is a typical effect for the inclusion of clay in a polymer
medium. Furthermore, the individual silanization led to
the highest transition temperatures, which might be due
to the advanced interaction/intercalation between the
nanoclay and the PMMA via hydrogen bonding.
Although the 2 %-silanized-clay-based nanocomposite
sample showed a very low storage modulus, its T
g
value
increased up to 96.68 °C, with an approximately 20 %
increase. Similar achievements for the same percentage
of filler were also observed for the surfactant-silanized
clay/PMMA and the neat clay/PMMA films with 18.8 %
and 12.73 % increments, respectively.
Based on the literature, the decrease of the tan  peak
is an indication of the reinforcement efficiency and
related to the degradation of mobile chains during the
glass transition.
5
Regarding Figure 4, nearly all the
nanocomposite films exhibited lower tan  peak values,
as expected. This may be attributed to the chemical and
physical absorption of the polymer molecules on the
particle surface, which resulted in the diminishing of the
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Materiali in tehnologije / Materials and technology 53 (2019) 1, 87–94 91

chain mobility.
5,25
Some composites, such as the 1 %
silanized clay/PMMA, the 2 % neat clay/PMMA and the
2 % surfactant-silanized clay/PMMA, showed broad
transition zones, unlike the other specimens. This type of
character is generally observed when the structure
possesses heterogeneity and a broader distribution of the
relaxation times.
27
In DMA studies, the loss modulus (E") represents the
viscous features of the samples as a function of time,
temperature or frequency. The loss modulus vs. tempe-
rature graphs of the produced films are seen in Figures
5a to 5c. As seen in the figures, the loss modulus of the
pure PMMA shows a single peak that points out its
amorphous nature. The E" peaks of the composite films
are shifted to higher temperatures with the introduction
of more nanoclay, independent of the modification type.
This effect may be due to the influence of the present
clay on the relaxation manner of the PMMA chains.
28
Another important finding is related to the loss modulus
behaviour of surfactant-silanized clay-based films.
Except for the 2 % sample, those composites showed the
highest loss transition temperatures, but lower modulus
values. So it can be concluded that the improved loss
modulus is a typical indication of the dominant viscous
character of surfactant-silanized composites.
3.3. Morphological characterization
The scanning electron microscope (SEM) images of
the neat PMMA and the nanoclay-based composites are
shown in Figures 6 and 7. During the SEM analysis, it
was difficult to capture the photographs with a fine/
precise resolution. Therefore, the whole images do not
have the same magnifications. Although the intercalation
or dispersion of the clay platelets in the polymer medium
is not sufficiently determined from these micrographs,
the distribution of filler provides fundemental ideas in
terms of the morphological aspects. The clay particles in
the matrix are lighter and generally observed as agglo-
merations or aggregates, as seen in Figure 6. Probably,
they can be regarded as tactoids, which are composed of
unseparated clay galleries. However, these agglomerated
particles usually show a narrow size distribution and
relatively good regularity.
In Figure 7a, the 2 % silanized clay/PMMA film
exhibited a dendritic like morphology, unlike the other
samples, which resulted in the highest T
g
. The formation
of the dendritic morphology is not as common as inter-
calated or exfoliated microstructures. According to the
literature,
29
a long or strong ultrasonic treatment pro-
motes the transformation of self-assembled lengthy rod
structures into the shortened morphologies. The me-
chanism consists of the fracturing of lengthy rods and
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92 Materiali in tehnologije / Materials and technology 53 (2019) 1, 87–94
Figure 6: SEM photographs of: a) Neat PMMA, b) 0.5 % silanized
clay/PMMA, c) 0.5 % surfactant-silanized clay/PMMA and d) 0.5 %
neat clay/PMMA
Figure 5: Loss modulus vs. temperature plots containing neat PMMA
and a) 0.5 % nanoclay/PMMA composite, b) 1 % nanoclay/PMMA
composite, c) 2 % nanoclay/PMMA composite

restacking into dendrites of short rods. The ultrasonic
treatment ensures sufficient energy for the hierarchical
transformation and the appearance of the dendrites be-
comes more regular in branching. In our study, the 2 %
silanized clay/PMMA was probably subjected to higher
ultrasonic vibration and due to the higher filler
concentration, the particles tended to form leaf dendrites.
This type of structure led to the increase of T
g
and the
decrease of the storage modulus.
The agglomerated morphology is more dominant for
the other composite specimens, as seen in Figures 7b
and 7c. Similar morphologies like in Figure 7 were also
present for the 1 % films; therefore, the SEM images of
those specimens are not included in this study. Although
the glass-transition temperatures of the composite films
increased with an increase of the clay concentration, the
poor dispersion of nano-filler seen in the SEM photo-
graphs might be the probable reason for the decrease of
the storage-modulus values.
4 CONCLUSIONS
In the present study the effects of different surface-
modification techniques and filler concentration were
examined for nanoclay/PMMA composite films. The
films were produced via a solution-casting technique and
their behaviours were determined depending on their
modification type. Based on the XRD characterization
results it was surprising that the presence of silane and
surfactant in the nanoclay structure led to the exist-
ence/increase of the amorphous phase. Although the
main purpose of this work is the application of organo-
philic modification and silane surface treatment together
for combining their synergetic effects, the produced
films did not satisfy the expectations in terms of storage
modulus (E'). However, the introduction of nanofiller led
to an increase of the glass-transition temperatures (T
g
)of
almost every composite film, independent of the modi-
fication technique. So it was concluded that the addition
of a larger nanoclay quantity enhances the adhesion of
the polymer and layered silicate. The individual silane
agent implementation was the most successful method
and the silanized composites generally exhibited the
highest stiffness (E') and transition temperature (T
g
), as
compared to the other samples. In addition, the loss
modulus (E") of the every composite film shifted to
higher temperatures with an increase of the nanoclay
concentration. This may be attributed to the effect of the
clay on the relaxation manner of PMMA chains and
according to the SEM images, the clay fillers are
generally observed as agglomerated particles, but they
showed a narrow size distribution and a relatively good
regularity.
Acknowledgment
Funding for this research was provided by the project
2016-069, Scientific Research Funds of Manisa Celal
Bayar University.
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