B. SUKSUT, S. DUANGSRIPAT: EFFECT OF GRAPHENE ON THE PROPERTIES OF EPOXIDIZED-PALM-OIL ...
457–464
EFFECT OF GRAPHENE ON THE PROPERTIES OF
EPOXIDIZED-PALM-OIL PLASTICIZED POLY(LACTIC ACID)
BIOPOLYMER NANOCOMPOSITES
VPLIV GRAFENA NA LASTNOSTI PLA BIOPOLIMERNIH
NANOKOMPOZITOV PLASTIFICIRANIH Z EPOKSIDIZIRANIM
PALMINIM OLJEM
Buncha Suksut
1*
, Sorawit Duangsripat
2
1
Faculty of Engineering and Technology, King Mongkut’s University of Technology North Bangkok,
Rayong Campus, Rayong 21120, Thailand
2
Haydale Technologies (Thailand) Company Limited, D510-D515, NIC2 Building l, Tower D, 141 Moo 9, Thailand Science Park,
Phaholyothin Rd., Khlong Luang, Pathumthani 12120, Thailand
Prejem rokopisa – received: 2019-07-03; sprejem za objavo – accepted for publication: 2019-12-12
doi:10.17222/mit.2019.140
This work focused on an analysis of the relationship between the morphology and properties of epoxidized palm oil (EPO)
plasticized poly(lactic acid) (PLA) filled with graphene (GP). Differential scanning calorimetry results showed that GPs can act
as nucleating agents for PLA, which decreased the cold crystallization temperature and increased the crystallinity. This
nucleating effect of the GP was less effective in the PLA/EPO blends, due to its preferred dispersion in the EPO phase. By
polarized light microscopy observation, the spherulite size of the PLA decreased with the presence of GP in the PLA/EPO
blends, while the EPO provided the larger spherulite size as compared to neat PLA. Nevertheless, the increase in crystallinity,
especially at high GP loadings, helped to retain the mechanical properties of the plasticized PLA.
Keywords: graphene, polylactic acid, nanocomposites, crystallization
V tem prispevku avtorji opisujejo raziskavo, ki se je osredoto~ala na analizo povezave med morfologijo in lastnostmi z
epoksidiziranim palminim oljem (EPO) plastificirane polilakti~ne kisline (PLA), polnjene z grafenom (GP). Rezultati
diferencialne vrsti~ne kalorimetrije (DSC) so pokazali, da GP lahko deluje kot sredstvo za tvorbo jeder (nukleacijo) PLA, kar
zmanj{uje hladno kristalizacijo in pove~uje kristalini~nost. Ta nukleacijski u~inek GP je manj u~inkovit v PLA/EPO-me{anicah,
zaradi njegove prednostne disperzije v EPO-fazi. Dodatna opazovanja v opti~nem polarizacijskem mikroskopu so pokazala, da
se velikost PLA-sferulita zmanj{uje s prisotnostjo GP v PLA/EPO-me{anicah, medtem ko EPO zagotavlja ve~jo velikost
sferulita v primerjavi s ~istim PLA. ^eprav GP pove~uje kristalini~nost, {e posebej pri njegovih ve~jih dele`ih, pomaga
ohranjati mehanske lastnosti plastificiranega PLA.
Klju~ne besede: grafen, polilakti~na kislina, nanokompoziti, kristalizacija
1 INTRODUCTION
Biodegradable polymer is of great interest as an
environmentally friendly material. Poly(lactic acid),
PLA, is the most widely used and fastest-growing class
of biodegradable polymer, which exhibits environmen-
tally friendly, good clarity, high strength and moderate
barrier properties. However, the problems of PLA are the
mechanical brittleness and slow crystallization rate,
inducing more difficult to control the processing. The
improvement of the mechanical brittleness can be done
by adding:
1) the filler particles as impact modifier,
2) polymer component such as thermoplastic or rubber
material in PLA matrix and
3) plasticizer.
1–5
To retain biodegradability property of PLA, many
studies have focused on blending PLA with other bio-
degradable materials deriving from renewable plants.
Epoxidized vegetable-oil-based plasticizer, such as
epoxidized soybean oil (ESO) and epoxidized palm oil
(EPO), is employed as a feasible alternative.
6,7
The increase in flexibility of plasticized PLA is
always accompanied by a drop in strength and stiffness.
8
One of the most feasible approaches to balance the per-
formance of polymer is the reinforcing of nanoparticles
into the polymer matrix, which exhibits an enormous
surface area, being larger by several orders of magnitude.
These nanofillers included clay, nanocellulose and
graphene (GP).
8–12
According to Cheing et al. the addi-
tion of a small amount of graphene nanoplatelet (xGnP)
(up to 0.3 w/%) improves the tensile properties of
PLA/EPO.
8
The further addition of xGnP provides a de-
crease of stiffness, strength and flexibility. Sriprachuab-
wong et al. attributes the highest elongation at the break
of PLA/EPO at an optimal GP loading of 0.6 w/%
13
However, both the stiffness and strength decreases
continually with increasing GP loading. The same effect
was observed for a PLA/clove essential oil (CLO) blend
Materiali in tehnologije / Materials and technology 54 (2020) 4, 457–464 457
UDK 67.017:620.1:665:620.3 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 54(4)457(2020)
*Corresponding author's e-mail:
buncha.s@eat.kmutnb.ac.th (Buncha Suksut)

with the addition of graphene oxide (GO) nanosheets.
12
Besides the reinforcement effect, the presence of nano-
filler is considered to change the morphological struc-
tures, thus the final properties of products. Therefore, the
main objective of this work is to focus on the influence
of GP on the PLA morphology as well as on the relation-
ship between the resulting morphology and properties of
composites.
2 EXPERIMENTAL PART
2.1 Materials
Commercial poly(lactic acid) (PLA LX175, Corbion
Purac) was used as a matrix in the present work. The
melt flow and the density of this product are 6 g/10 min
(210 °C/2.16 kg) and 1.24 g/cm
3
, respectively. The PLA
was dried at 60 °C for 12 h in an oven before use.
Epoxidized palm oil (EPO) (Multi Ple Plus Company
Limited) was used as a plasticizer. Graphene (GP) syn-
thesized by electrolytic exfoliation under the condition
described in
13
was supported by Haydale Technologies
(Thailand) Company Limited.
2.2 Preparation of PLA/EPO/GP nanocomposites
In order to obtain a homogeneous nanoparticle dis-
persion, a masterbatch preparation was adopted for the
compounding of nanocomposites. PLA/EPO blends with
and without 0.3 w/% of GP were first prepared using an
internal mixer (MX500, Chareontut) at a mixing
temperature of 190 °C and a rotor speed of 60 min
–1
for
20 min. The PLA/EPO composition at a weight ratio of
97:3 was used. This composition was reported to yield
the optimal mechanical properties.
14
The masterbatches
were cooled in air for 30 min before grinding with a
mechanical grinder. Because of the limitation of the
yielding of the GP from electrolytic exfoliation
preparation and the requirement of transparent samples,
the maximum concentration of GP in this work was
0.2 w/%. In the second step, the masterbatches were then
diluted to the designed GP concentration varied from
0.02 to 0.20 w/% by a co-rotating twin-screw extruder
(CTE-D22L32, Chareontut) at a screw speed of 60 min
–1
.
The temperature was set from 190 °C near the hopper to
200 °C at the die. The diameter of the screw was 22 mm
and the L/D (length/diameter) ratio was 32.
After extrusion, the neat PLA and its nanocomposites
were injection molded (100ECS, JSW) to tensile test
samples according to ASTM D638 type I and impact test
samples according to ASTM D256. The temperatures
were set from 180 °C near the hopper to 210 °C at the
nozzle. A mold temperature of 40 °C and an injection
rate of 10 ccm/s were used.
2.3 Characterization of PLA/EPO/GP nanocomposites
The structure of the GP synthesized by electrolytic
exfoliation was characterized by Raman spectroscopy
(Ram II, Bruker). The morphology of the GP and
fractured surface of PLA and its nanocomposites after
the impact test were examined with a scanning electron
microscope (SEM, model JSM 6400, JEOL) at room
temperature. An acceleration voltage of 20 kV was used
to collect the SEM images for the sample. The fracture
surface sample was coated with gold for 3 min before
analysis.
In order to reveal the dispersion of graphene in
PLA/EPO/GP nanocomposites, a microtomed thin
section of 10 μm cut from the injection-molded plate was
applied onto a glass slide and covered by a cover slip.
The sample was then analyzed with a transmitted-light
microscope (DM2700M, Leica).
The spherulitic structure of PLA, as obtained from
the isothermal crystallization, was observed under a pol-
arized optical microscope (DM2700M, Leica) equipped
with a heating stage (LTS420, LINKAM). The thin
section of 10 μm was heated to 210 °C on the heating
stage and kept for 5 minutes at 210 °C to erase the pre-
vious processing history. It was then cooled to 120 °C,
and held constant until the completion of the crys-
tallization.
The thermal properties were determined using a
differential scanning calorimeter (DSC, Q200, TA
instruments) equipped with a Refrigerated Cooling
Systems 90 (RCS90). Indium was used as a reference
material to calibrate both the temperature scale and the
melting enthalpy before the samples were measured in
alternate runs and the baseline was subtracted. The
calorimeter was purged with nitrogen gas throughout the
measurement. The weight of each sample, between 5 and
10 mg, was placed in an aluminium pan and the pan was
then completely sealed with an aluminium lid.
The sample was initially heated from 0 °C to 210 °C
at the rate of 20 °C/min and held for 5 min at 210 °C to
ensure the complete melting of the previous crystals and
to erase their process history. Subsequently, the sample
was cooled to 0 °C at the rate of 10 °C/min. The glass-
transition temperature (T
g
), melting temperature (T
m
),
peak crystallization temperature during heating (T
cc
) and
degree of crystallinity (%X
c
) from the heat of fusion
were determined.
Tensile tests were conducted using a universal testing
machine (Model 25 ST, Tinius Olsen) with a load cell of
5 kN and a crosshead speed of 5 mm/min at 25 °C. A
minimum of five specimens were used for each compo-
sition. The measurements of elastic modulus, stress at
break and elongation at break were recorded. All the im-
pact test samples were notched using a V-notch sampling
machine (GT-7016-A2, Gotech Testing Machienes INC.)
with a notch angle of 45° having a radius of 0.25 mm
and a depth of 2.54 mm. The depth of the specimens
after being notched was 10.20±0.05 mm. A notched Izod
impact test was performed according to ASTM 256
using an impact testing machine (IT 504, Tinius Olsen).
The pendulum energy of 5.64 J was used at 25 °C. A
B. SUKSUT, S. DUANGSRIPAT: EFFECT OF GRAPHENE ON THE PROPERTIES OF EPOXIDIZED-PALM-OIL ...
458 Materiali in tehnologije / Materials and technology 54 (2020) 4, 457–464

minimum of five specimens was tested for each compo-
sition.
3 RESULTS AND DISCUSSION
Figure 1 shows the corresponding Raman spectra of
GP used in this research and typical graphite powder. It
can be seen that the Raman spectra of both the GP and
the graphite contain D, G and 2D bands, as the major
peaks at around 1356 cm
–1
, 1587 cm
–1
and 2700 cm
–1
,
respectively. A sharp G band is an in-plane vibrational
mode that involves sp
2
hybridized carbon atoms that
comprise the graphene sheet. The D band represents the
disorder or the defect band and is generally weak in
graphite. The 2D band (the second-order D band) is the
result of a two phonon lattice vibration process and is
always a strong band in the graphene.
15,16
Furthermore,
the G band is stronger than the 2D band in the spectrum
of graphene, a multilayer structure.
17
This confirms that
the electrolytic exfoliation method provides graphene
sheets with multilayers of sp
2
-bonded carbon.
Representative SEM images of GP powder are dis-
played in Figure 2 where the GP particles were agglo-
merated after drying. These SEM images also reveal the
thickness of the GP plate in the size range 30–100 nm.
This confirms that the GPs used in this research are on
the nanoscale.
Figure 3 shows images of PLA/EPO with and with-
out GP samples. These optical images show the micro-
dispersion of the GP in the composites. It can be seen
that there are some visible agglomerates with a size less
than 1 μm. However, these small agglomerates are uni-
formly distributed and homogeneously dispersed in the
PLA/EPO blends.
In order to clarify the influence of the GP nanopart-
icles on the crystallization of the nanocomposites, DSC
measurements of neat PLA, PLA/GP and PLA/EPO/GP
nanocomposites were performed. The DSC second
heating thermograms of the selected samples are pre-
sented in Figure 4. T
g
, T
cc
(determined at the peak of the
exothermic area), T
m
(determined at the peak of the
endothermic melting area) and H
m
(the measured heat
of fusion) are observed. All results derived from the
second heating thermograms are listed in Table 1.Itcan
B. SUKSUT, S. DUANGSRIPAT: EFFECT OF GRAPHENE ON THE PROPERTIES OF EPOXIDIZED-PALM-OIL ...
Materiali in tehnologije / Materials and technology 54 (2020) 4, 457–464 459
Figure 3: Representative transmitted-light images of: a) PLA/EPO, b)
PLA/EPO/GP0.02, c) PLA/EPO/GP0.1 and d) PLA/EPO/GP0.2,
scalebar is 20 μm Figure 1: Raman spectrum of electrolytic exfoliation graphene
Figure 2: SEM micrographs of electrolytic exfoliated graphene
powder at: a) 10000× and b) 30000×

be seen that, a single T
g
peak appeared at around
60–62 °C for all materials. This small hysteresis peak
associates with physical relaxation of the molecular
chain.
18
As shown, the T
g
slightly decreases with the
presence of EPO (about 2 °C) as compared to neat PLA.
This indicates that EPO is partially miscible with PLA,
increasing the chain mobility. This has been reported that
the carboxyl end groups of thermoplastic polyester are
miscible with epoxy resins during high-temperature
mixing.
6,19
In contrast, such a reduction in T
g
is not ob-
served for the PLA/GP and PLA/EPO/GP nanocompo-
sites, indicating that GP nanoparticles have no impact on
the T
g
of the PLA matrix. Similar to the T
g
, the incor-
poration of GP does not significantly change the T
m
of
the PLA for both PLA/GP and PLA/EPO/GP.
In the present work, the PLA does not crystallize
during cooling for all the materials (not shown here).
The crystallization of all the samples occurs during
second heating (cold crystallization). It is known that
lower T
cc
initiates faster crystallization. The exothermic
peak of cold crystallization of neat PLA is found at
129.0 °C. The incorporation of 0.10 w/% of GP shifts
approximately 4 °C to lower temperatures (the T
cc
de-
creases from 129.0 C to 125.4 °C), implying faster crys-
tallization. The results suggest that the GP nanoparticle
act as nucleating agents for the PLA. In the hetero-
geneous nucleation, the nucleating agent helps lower the
free-energy barrier, thus favoring faster nucleation.
20
In
the case of the incorporation of EPO, the DSC thermo-
gram of PLA/EPO shows a very weak and broad
exothermic peak appearing at the temperature of
131.0 °C, which is higher than that of neat PLA. This
implies that EPO retards the ability for the cold
crystallization of PLA. The retarding effect of EPO still
affects the PLA crystallization in PLA/EPO/GP0.02 and
PLA/EPO/GP0.1. Nonetheless, the DSC thermogram of
PLA/EPO/GP0.2 becomes a sharper and narrower
exothermic peak in comparison with PLA/EPO. The T
cc
of PLA/EPO/GP0.2 is lower than that of PLA/EPO, but
it is higher than that of PLA/GP0.1. This could be the
result of the competition between the nucleation effect of
the GP and retarding the effect of EPO. This finding
B. SUKSUT, S. DUANGSRIPAT: EFFECT OF GRAPHENE ON THE PROPERTIES OF EPOXIDIZED-PALM-OIL ...
460 Materiali in tehnologije / Materials and technology 54 (2020) 4, 457–464
Figure 4: DSC second heating thermograms of neat PLA and
PLA/EPO blends with and without GP
Figure 5: Polarized optical micrographs of PLA spherulites after isothermal crystallization at 120 °C in: a) neat PLA, b) PLA/EPO,
c) PLA/EPO/GP0.1 and d) PLA/EPO/GP0.2

deduces that the nucleating effect induced by the GP
nanoparticles dominates over the retarding effect of the
EPO only at high GP loadings (0.20 w/%).
Table 1: DSC second heating results of PLA and PLA/EPO blend
with and without GP
Samples T
g
,°C T
cc
,°C T
m
,°C  H
m
, J/g
PLA 62.2 129.0 152.1 14.3
PLA/GP0.02 62.3 130.3 152.4 13.1
PLA/GP0.10 62.0 125.4 152.9 21.7
PLA/EPO 59.9 131.0 150.9 5.0
PLA/EPO/GP 0.02 59.9 133.0 152.2 4.4
PLA/EPO/GP 0.04 60.1 131.2 152.0 5.8
PLA/EPO/GP 0.06 59.8 130.9 151.4 6.5
PLA/EPO/GP 0.08 60.4 130.7 152.2 8.6
PLA/EPO/GP 0.10 60.4 131.0 152.5 8.1
PLA/EPO/GP 0.20 60.0 128.4 152.2 16.9
A significant increase of the heat of fusion values of
the PLA is observed with an addition of 0.10 w/% of GP,
as compared with the neat PLA, which had a  H
m
,o f
14.3 J/g. It is well known that a higher heat of fusion
corresponds to a higher degree of crystallinity. However,
a huge depression of the heat of fusion is observed with
the addition of EPO. The results are in good agreement
with the previous report of F. Ali.
6
In PLA/EPO blends,
the heat of fusion slightly increases with an increasing of
the GP content up to 0.10 w/% of GP and reached the
maximum value at the GP content of 0.20 w/%, which is
about three times greater than that of the PLA/EPO.
Thus it is deduced that the GP can be considered as the
most effective nucleating agent for neat PLA, but it may
be less effective in PLA/EPO. It could be though that the
GP preferentially dispersed in the EPO phase instead of
the PLA, leading to less nucleation ability for the PLA.
The nucleation effect of the GP can be confirmed by an
analysis of the spherulitic development via a thermo-
optical technique.
Polarized optical micrographs of neat and plasticized
PLA samples after melting and cooling to the isothermal
crystallization of 120 °C are shown in Figure 5. The neat
PLA forms a well-defined Maltese cross pattern of sphe-
rulites with a average diameter of about 20 μm (Figure
5a). The spherulite size seems to increase as a result of
blending PLA with EPO (Figure 5b). This confirms that
the crystallization behaviors of PLA are hindered with
the existence of EPO, which is in a good agreement with
the DSC results. The presence of GP tends to decrease
the PLA spherulite size (Figures 5c and 5d). The results
indicate that the GP can act as a nucleating agent, where
a high number of heterogenous nuclei lead to smaller
spherulites. This result is in good agreement with DSC
thermograms in the previous discussion.
The Young’s modulus and tensile strength at yield of
the PLA and PLA/EPO samples are plotted in Figures 6.
The incorporation of EPO decreases the Young’s mo-
dulus of the PLA as the plasticizing effect of the EPO. It
can also be seen that both the Young’s modulus and the
B. SUKSUT, S. DUANGSRIPAT: EFFECT OF GRAPHENE ON THE PROPERTIES OF EPOXIDIZED-PALM-OIL ...
Materiali in tehnologije / Materials and technology 54 (2020) 4, 457–464 461
Figure 7: Tensile strain at break (left) and impact strength of neat
PLA and PLA/ESO blends with and without GP
Figure 6: Young’s modulus (left) and tensile strength at yield (right)
of neat PLA and PLA/ESO blends with and without GP

tensile-strength evaluation does not well define the
dependence of GP loading, and seems not to be signifi-
cantly affected by the GP addition. From the tensile
results, the reinforcement effect of the GP on the
PLA/EPO blend is ambiguous. This could be because of
poor nanoparticle/matrix interfacial adhesion, preferen-
tial dispersion of the GP in the EPO rather than in the
PLA and/or GP loading. Due to its ability to crystallize,
the mechanical properties of PLA not only depend on the
reinforcement of the nanoparticle, but also its crys-
tallinity and spherulite size. The microscopy analysis
reveals the reduction in the size of spherulites with the
incorporation of GP. A smaller spherulite generally
causes a tensile strength.
21
On the other hand, a higher
crystallinity of PLA in PLA/EPO/GP0.2 results in a
small increase in the Young’s modulus. It is the
crystalline phase rather than the amorphous phase that is
stronger and more difficult to deform. C. Sriprachuab-
wong et al.
13
reported that the Young’s modulus and
tensile strength of the PLA/EPO blend decrease linearly
with the increasing GP loading (ranged from 0.2 w/% to
0.8 w/%), attributed to the weak interface adhesion
between the GP and PLA. B. W. Chieng et al.
22
also
found a similar result of the reduction in tensile strength
on hybrid plasticized PLA/xGnP nanocomposites.
Although the Young’s modulus of the hybrid plasticized
PLA with 0.1 w/% loading was about 10 % greater than
that of the hybrid plasticized PLA, it decreased sig-
nificantly with increasing xGnP loading (up to 1 w/%).
As is well known, the plasticization of EPO normally
gives high flexibility. As expected, the elongation at
break of the PLA is enhanced with the addition of EPO,
as shown in Figure 7 (left), and the large standard de-
viation should be noted. In addition, elongation at break
increases with increasing GP loading up to 0.04 w/%,
then decreases as the GP loading increases further to
0.2 w/%. The increase in the elongation at break of
PLA/EPO at lower GP loading could be explained by the
reduction of PLA spherulite size. As is well known, the
spherulitic structure occurs by the stack of folded chain
lamellar crystal. The connections between lamellar
crystals are called tie-molecules. The smaller spherulite
size leads to a larger number of tie-molecules, resulting
in an increase of the flexibility and impact strength.
23
On
the other hand, when the GP loading is increased, the
spherulite size is less effective on the improvement of
flexibility. This result agrees with Chieng et al., reports
which stated that the decrease of elongation at break
with increasing filler loading may be associated with a
large aspect ratio of filler and the interfacial adhesion
between the filler and the polymer matrix.
8
This restricts
the effectiveness of the stress transfer between the
polymer matrix and the filler. Figure 7 (right) presents
the impact strength of PLA/EPO/ GP nanocomposites.
As seen, the effect of GP nanoparticles is not
pronounced in the impact-strength improvement. The
presence of GP retains the impact strength of the
PLA/EPO over the range of GP loading, even the
reduction of the elongation at the break of PLA/EPO at a
high GP loading is found. This could be due to the
differences in the stain rate of two testing methods, as
related to different applications.
From the above discussion, we can conclude that the
mechanical properties of the PLA/EPO blend is
B. SUKSUT, S. DUANGSRIPAT: EFFECT OF GRAPHENE ON THE PROPERTIES OF EPOXIDIZED-PALM-OIL ...
462 Materiali in tehnologije / Materials and technology 54 (2020) 4, 457–464
Figure 8: SEM micrographs of fractured surface of: a) Neat PLA, b) PLA/EPO, c) PLA/EPO/GP0.02 w/%, d) PLA/EPO/GP0.10 w/%

determined not only by nanoparticle/matrix interfacial
adhesion and nanoparticle loading, but also the main
morphological parameters, such as the degree of
crystallinity and the spherulite size. The interplay bet-
ween these factors cannot always be separated.
The SEM micrographs revealed a rather brittle frac-
ture of neat PLA without any visible plastic deformation
on the smooth fractured surface of the impact sample, as
shown in Figure 8a). The addition of EPO ( Figure 8b)
is brought into relative rough fractured surface with a
fibrous structure, which is evidence of the ductile frac-
tures.
5
In PLA/EPO/GP nanocomposites, the GP nano-
particles on the fractured surface are not easily
distinguishable, even from high magnification due to the
surface sample instability when a large magnification is
attempted. However, the SEM micrographs of the impact
fractured surface of the PLA/EPO/GP nanocomposites
(Figure 8c and 8d) retain a fibrous structure on the
rough fractured surface. From this we can deduce that
the toughness improvement of the PLA is contributed by
the plasticization of the EPO.
4 CONCLUSIONS
This work presents the influence of GP nanoparticles
on the morphology of PLA and the mechanical
properties of the PLA/EPO blend. The crystallization of
the PLA in the PLA/EPO/GP system is influenced by a
competition effect of the EPO as plasticizer and GP as
the nucleating agent. In neat PLA, GP induces a higher
degree of crystallinity of PLA, along with the lower cold
crystallization, but its effectiveness is less pronounced in
PLA/EPO. A drop in the ability to nucleate the GP in the
PLA/EPO blend could be due to the preferred dispersion
in the EPO phase. In addition, the resulting tensile pro-
perties of PLA/EPO filled with GP is a result of an
efficiency of stress transfer and the morphology of the
PLA. As of interest, with higher crystallinity obtained in
the presence of GP, a small increase in the Young’s
modulus and tensile strength of PLA/EPO can be
attained.
Acknowledgment
The authors would like to thank the Faculty of
Engineering and Technology, King Mongkut’s Uni-
versity of Technology North Bangkok, Thailand, for
experimental support of this work. The authors also
thank the Haydale Technologies (Thailand) Company
Limited for the supply of the graphene.
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