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Corrosion Engineering, Science and Technology
The International Journal of Corrosion Processes and Corrosion Control
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The use of montmorillonite organoclay in
preparation of UV-cured DGBA epoxy anticorrosive
coatings
J. L. Varela Caselis, E. Rubio Rosas, J. D. Santamaría Juárez, J. A. Galicia
Aguilar, M. Sánchez Cantú, O. Olivares Xometl & M. Morales Sánchez
To cite this article: J. L. Varela Caselis, E. Rubio Rosas, J. D. Santamaría Juárez,
J. A. Galicia Aguilar, M. Sánchez Cantú, O. Olivares Xometl & M. Morales Sánchez
(2018) The use of montmorillonite organoclay in preparation of UV-cured DGBA epoxy
anticorrosive coatings, Corrosion Engineering, Science and Technology, 53:5, 362-369, DOI:
10.1080/1478422X.2018.1474329
To link to this article: https://doi.org/10.1080/1478422X.2018.1474329
Published online: 15 May 2018.
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2. The use of montmorillonite organoclay in preparation of UV-cured DGBA epoxy
anticorrosive coatings
J. L. Varela Caselisa
, E. Rubio Rosasa
, J. D. Santamaría Juárezb
, J. A. Galicia Aguilarb
, M. Sánchez Cantú b
,
O. Olivares Xometl b
and M. Morales Sánchez b
a
Centro Universitario de Vinculación, Benemérita Universidad Autónoma de Puebla, Puebla, México; b
Facultad de Ingeniería Química, Benemérita
Universidad Autónoma de Puebla, Puebla, México
ABSTRACT
In this study, montmorillonite organoclay (OMMT) at various concentrations were tested as nanofillers
in preparation of UV-cured DGEBA epoxy anticorrosive coatings and applied on carbon steel
substrates. The effect of incorporating different compositions of OMMT in UV-cured Araldite 506
coatings on the aqueous corrosion resistance of carbon steel in 5 wt-% aqueous NaCl electrolyte
was evaluated. Analysis showed that the OMMT was homogenously dispersed in the polymer
matrix. The result of X-ray diffraction showed that a certain degree of intercalation occurred for the
OMMT in the polymer matrix. The OMMT addition affects the UV cured of the Araldite 506, as
evidenced by Fourier transform infrared spectroscopy. The anticorrosive properties were evaluated
by electrochemical impedance spectroscopy at various exposure periods. Coatings with 3 wt-%
OMMT possessed the best corrosion performance among the coating specimens. In fact, the NC3
coating provided corrosion protection properties even after a long exposure to NaCl solution.
ARTICLE HISTORY
Received 20 September 2017
Accepted 25 April 2018
KEYWORDS
Epoxy resin; coatings; UV
cured; montmorillonite;
nanocomposites
Introduction
Polymer/clay nanocomposites are compounds in which
nanoclay particles are distributed in a polymer matrix. Poly-
mer/clay nanocomposites have been used as anticorrosive
coatings to prepare a series of polymeric matrices [1–3].
These inorganic materials have effectively increased the diffu-
sion pathways of water and destructive ions, thereby enhan-
cing the protection performance of the coatings.
The nanoclays lamellar elements display high in-plane
strength, stiffness and high aspect ratios [4–7]. The nanocom-
posites containing montmorillonite show remarkable barrier
properties to gases and moisture as well as very good resist-
ance to staining [8–10]. Thus, it is particularly interesting
the preparation of montmorillonite reinforced polymeric
thin films for coating application. The aim of the addition
of the nanoclay inorganic particles is to increase barrier effect,
strength and other properties of the polymeric films [11].
Epoxy resins are widely used as a basis for anticorrosive
coatings because of their excellent physico-chemical proper-
ties [12–14]. Within the epoxy resins, the most conventional
ones are glycidyl ethers of bisphenol A (DGEBA) and cycloa-
liphatic epoxies. DGEBA-based resins are cured thermally via
an addition mechanism with diamines, while cycloaliphatic
epoxies are commonly cured with anhydrides [15–17] or
homopolymerised via a cationic mechanism [18–20] initiated
by UV radiation.
UV-curing processes are becoming a very important
alternative to the thermal process due to their particular
characteristics: allows a fast transformation of the liquid
monomer into the solid film with tailored physico-chemical
and mechanical properties [21–23]. This process [24] is
very fast and environmentally friendly since complete conver-
sion is usually obtained in seconds, the substrate does not
need to be heated as in the traditional thermal curing (there-
fore it guarantees the saving of energy), the polymerisation
takes place in the bulk and no solvent is employed (thus
the release of volatile organic compounds is minimised).
UV irradiating a suitable photoinitiator can generate both
radical and cationic species; therefore, the reaction mechan-
ism is either radical or cationic.
Photopolymerisation has advantages in the synthesis of
nanocomposites due to fast reaction kinetics that accelerates
polymeric network formation over inorganic phase separ-
ation or aggregation, a quick conversion solidifies the med-
ium around the dispersed particles and suspends the
dispersion state attained in initial material. Previous works
have shown the possibility of obtaining intercalated nano-
composites in the presence of epoxy resins, using cationic
photopolymerisation [25,26].
Numerous reports have already demonstrated the positive
effects of nanoclays on epoxy resins [8,27–29]. Both thermal-
cured DGEBA epoxy-based nanocomposite and UV-cured
cycloaliphatic epoxy coatings have been extensively studied
[30–33], however, few studies have reported on the prep-
aration and anticorrosive performance of UV-cured nano-
composite coatings based on DGEBA and montmorillonite
[34]. It is interesting to evaluate as an alternative the potential
use of DGEBA epoxy, since these resins are less expensive
than the cycloaliphatic ones, and may have an impact on
the cost of preparing UV-cured coatings.
Thus, the purpose of this study was characterising by
physical techniques, the synthesised coatings and monitoring
the effect of the addition of an organophilic montmorillonite
on the corrosion performance of UV-cured Araldite 506
epoxy resin coatings applying electrochemical impedance
spectroscopy (EIS).
© 2018 Institute of Materials, Minerals and Mining Published by Taylor & Francis on behalf of the Institute
CONTACT J. L. Varela Caselis jvarela11@yahoo.com.mx Centro Universitario de Vinculación, Benemérita Universidad Autónoma de Puebla, Prol. 24 sur y Av.
San Claudio, C.U. Col. San Manuel, Puebla C.P. 72570, México
CORROSION ENGINEERING, SCIENCE AND TECHNOLOGY
2018, VOL. 53, NO. 5, 362–369
https://doi.org/10.1080/1478422X.2018.1474329

3. Experimental
Materials
Samples were prepared using Araldite 506 epoxy resin
(A506), having an epoxide equivalent weight of 172–
185 Da, and the cationic photoinitiator triarylsulfonium hex-
afluorophosphate, mixed 50% in propylene carbonate.
OMMT, a nanoclay’s surface-modified that contains 20–
30 wt-% methyl dihydroxyethyl hydrogenated tallow
ammonium. All reagents were supplied from Sigma Aldrich.
Preparation UV-cured coatings
The OMMT was dispersed in liquid resin A506 at concen-
trations of 0, 1, 3 and 5 wt-% and abbreviated as NC0,
NC1, NC3 and NC5, respectively, where NC0 was reference
sample. The procedure of the clay/epoxy dispersion was as
follows: mechanical mixing for 2 h at 60°C, then sonication
for 2 h at room temperature and finally 2 wt-% cationic
photoinitiator was added. The obtained solution was coated
onto cold-rolled carbon steel panels using a wire-wound
applicator with substrates being decreased by acetone before-
hand. Finally, they were exposed for 5 min to UV light using a
20 mWcm−2
lamp and 110–113 µm thickness films were
obtained. All the polymerisation reactions were performed
at room temperature.
Scanning electron microscopy (SEM) images of the nano-
composite coatings were obtained on a JEOL JSM-6610LV
equipped with an Oxford Instruments energy dispersive X-
ray spectroscopy. The samples were placed on conductive
aluminium tape and coated with gold in a sputtering unit
(Denton Vacum, DESK v SCD-030) before SEM observation.
SEM observations were carried out by use of secondary elec-
tron detector on coatings samples working in high vacuum
mode and at 20 kV of accelerating voltage. X-ray diffraction
(XRD) data were collected on a Bruker diffractometer
model D8 Discover in a Bragg–Brentano geometry using
CuKα radiation (λ = 0.15418 nm) and step-scan mode
(range: 3–80° of 2θ, step-time: 0.60 s, step-width: 0.04°).
Thermal stability of the samples was determined by thermo-
gravimetric analysis (TGA) on a Netzsch thermal analyser
model STA 449 F3 Jupiter from 25 to 800°C under a nitrogen
atmosphere. The heating rate was 10°C min−1
. Fourier trans-
form infrared spectroscopy (FTIR) was carried out on a Bru-
ker spectrometer model Vertex 70, in the interval of 500–
4000 cm−1
.
Electrochemical studies
The anticorrosive properties were investigated using EIS.
Coated samples were exposed to a 5 wt-% NaCl water sol-
ution for 2000 h. A three-electrode cell arrangement with
coated carbon steel substrates as a working electrode, graphite
bar as a counter electrode and a saturated calomel electrode as
reference electrode, were used. AC impedance measurements
were conducted on open circuit potential using a Gamry,
Reference 600 potentiostat/galvanostat/ZRA over a frequency
range of 100 kHz–10 mHz, the amplitude of sinusoidal vol-
tage was 10 mV. Interpretation of the impedance data was
performed using the Gamry Instruments Echem Analyst fit-
ting program, version 6.25.
Results and discussion
Coating’s microstructure
The homogeneity and morphology of the organoclay dis-
persed in the epoxy matrix was investigated by SEM, since
the difference in scattering densities of the clay and the
epoxy matrix facilitates their differentiation. Figure 1(a,b)
shows the surfaces images of the cured epoxy resin (NC0)
and the NC3 sample.
The epoxy coating NC0, had a relatively smooth surface
morphology, with no cracks or discontinuities being detected
(Figure 1(a)). SEM images show that the brittle fracture sur-
face of the cured epoxy resin (NC0) becomes rougher when
the clay is incorporated into the polymer matrix (Figure 1
(b)), however, clay distribution is uniform and homogenous
on the NC3 coating surface. Figures 1(c,d) shows a cross-sec-
tion of the coating, where an excellent adhesion can be
observed in the coating/metal interface. The coatings thick-
ness was in the range of 110–113 µm.
The OMMT’s dispersion in epoxy resin was also studied by
the XRD technique. Figure 2 illustrates the XRD patterns of
pure organoclay (OMMT), the reference sample NC0 (cured
epoxy resin) and the composite samples NC1, NC3 and
NC5. Sample OMMT presented the characteristic reflections
of montmorillonite with an intense and well-defined reflection
of the (001) plane at 4.88° and a weak reflection generated by
the (002) plane at 9.5° of 2θ. The difference of the 2-theta pos-
ition of the (001) reflection compared to other reports [35] was
attributed to the organic section of the raw material (see exper-
imental section) which is incorporated into the montmorillo-
nite structure causing its lattice expansion. On the other hand,
the NC0 sample exhibited a broad signal centred at 18° which
is related to the amorphous structure of cured epoxy resin. In
NC1 sample, the absence of the two characteristic montmoril-
lonite reflections was attributed to the apparatus detection
limits. However, in samples with higher clay loadings (NC3,
NC5) the (001) plane was clearly identified indicating that
the fraction of retained organoclay in the polymer matrix
increases with increasing the clay content in the sample [36–
38]. It has been reported that this peak reveals that XRD’s
analysis as sufficiently sensitive technique for detecting the
presence of organoclay in NCs and for its quantification [39].
It is important to remark that a shift towards lower 2θ
values of the (001) reflection was identified in NC3 and
NC5 samples (d(100) = 20.3 and 20.1 Å, respectively) com-
pared to NC0 (d(100) = 18.1 Å) which is indicative of a lattice
expansion. In this context, it was assumed that this expansion
was caused by the polymer incorporation into montmorillo-
nite’s structure.
The synthesised samples were analysed by FTIR spec-
troscopy with the aim of monitoring the UV curing reaction
of epoxy resin. Epoxy group conversion was followed by
monitoring the decrease of the absorbance of the oxirane
group band in the region 970–914 cm−1
. Figure 3, shows
the spectra before and after UV-irradiation of the coating.
The characteristic absorption bands of the samples A506,
NC0, NC1, NC3 and NC5 are shown in the figure. The
absorption band located at 914 cm−1
is associated to the oxi-
rane group. This band is not present in NC0 sample, but was
increased with larger loads of OMMT, then the presence of
this band is observed with greater intensity in the NC5
sample, this band is associated to unreacted oxirane. Santosh
CORROSION ENGINEERING, SCIENCE AND TECHNOLOGY 363

4. et al. [40] found that the presence of amines inhibited the rate
of photopolymerisation and the degree of inhibition
depended on the basicity of the amine. Based on the above
it can be explained that UV cured is inhibited by the amine
group contained on the OMMT and inhibition increases as
the organoclay concentration is increased.
Thermal properties of epoxy NCs
Thermal stability of the epoxy resin was investigated by TGA.
Figure 4 shows OMMT, NC0, NC1, NC3 and NC5
thermograms obtained under nitrogen atmosphere in the
temperature range from 25 to 800°C. The initial degradation
temperature (IDT), and the residual mass of samples are pre-
sented in Table 1. IDT, defined as the temperature of the 5%
weight loss, was used as a thermal stability indicator of the
samples. For the TGA, the OMMT is decomposed into four
steps: the first one in the range of 25–90°C related to clay
dehydration and three steps more in the range of 208–800°
C related to the decomposition of clay modifier [41]. At
800°C the clay modifier is completely decomposed and only
the thermally stable inorganic clay (∼75 wt-%) remained.
Structural decomposition of NC0, NC1 and NC3 samples
Figure 1. SEM micrographs of the surface: (a) NC0; (b) NC3; (c,d) NC0 and NC3 cross-section.
Figure 2. XRD diffractograms of OMMT, NC0, NC1, NC3 and NC5 epoxy/organo-
clay composites.
Figure 3. FTIR spectra of A506, NC0, NC1, NC3 and NC5 coatings, the epoxy
absorption peaks are indicated in the spectra.
364 J. L. VARELA CASELIS ET AL.

5. took place approximate from 267 to 445°C, and consists of two
decomposition steps related to breaking of the chemical bonds
of uncured epoxy resin (320–380°C) and of epoxy network
(380–445°C) [42,43] while structural decomposition of NC5
sample took place at lower temperature, approximate 100 to
445°C, this indicates a higher content of uncured epoxy
resin, as confirmed by FTIR spectra. The residual mass of
NC0 sample at 800°C, 17.5 wt-%, indicates that some degra-
dation products did not volatilise, while the higher residual
mass are found for NC1, NC3 and NC5 (Table 1) due to the
presence of inorganic clay. The residual mass increased with
the level of clay loading; however, residual mass was affected
due to the presence of moisture in the clay which was 2 wt-
%. The inset in Figure 4 and Table 1 show that IDT of NC0
is the highest, while sample NC5 has the lowest IDT of the
order 93°C lower than IDT of NC0 sample. As clay content
increases, the IDT starts to decrease. One cause of these results
may be due to incomplete curing of the samples containing
OMMT, this is confirmed by Figure 3, where the sample
NC5 shows a band of increased intensity of the oxirane
group indicating that this sample had the poorest curing com-
pared to the other samples. Incomplete curing indicates the
presence of unreacted monomers have not reacted completely,
which degrade more rapidly at a lower temperature, therefore
the nanocomposite is less stable. This behaviour was especially
pronounced at the sample NC5, which had the lowest IDT.
Anticorrosive properties of the coatings
Differences were evident in electrochemical behaviour of the
coating systems and how these changed in respect of exposure
time, both of which may be studied and analysed in detail by
fitting resistive capacitive electrical equivalent circuits to the
impedance data using an analysis software and by quantifying
values for the circuit components.
Figure 5 shows the electrical equivalent circuit (EEC) that
models electrochemical behaviour of the coated steel panels
in exposure to 5 wt-% NaCl solution. The presented model
employs constant phase elements (CPE) instead of capacitors,
with CPE equalling to 1/C(jω)α
, where α is the frequency dis-
persion factor that ranges from 1 to 0 (when α = 1, C can be
considered a real capacitance).
Figure 6 shows Bode plots from EIS data resulting from
sample immersion in 5 wt-% NaCl solution. The Bode plot
is a straight line with a negative slope (−1) in the first
times, which indicates that the coating acts as a perfect
capacitor (Figure 6(a)) and show extremely high resistance
of the pore (Rp) for nanocomposite coatings.
After 350 h of immersion, the impedance value is lower
than its initial state. The impedance of neat epoxy (NC0)
coated sample decreases to 4.5 GΩ cm2
as revealed by the
horizontal intersection of the graph with impedance mod-
ulus axis in Bode plot (Figure 6(b)) while the impedance
for NC1, NC3 and NC5 were 2.2, 9.3 and 0.27 GΩ cm2
,
respectively. In the case of samples with 700 h of immersion
(Figure 6(c)), the impedance value is much lower than its
initial state. After 700 h of immersion, NC3 sample pro-
vided a better barrier protection (2.9 GΩ cm2
) than the
others. After 850 h of immersion, NC3 Bode’s plot shows
the highest impedance (3 GΩ cm2
), followed by NC0
(1.9 GΩ cm2
), NC1 (333 MΩ cm2
) and NC5
(220 MΩ cm2
). This indicates that NC1 and NC5 coatings
have decreased their protective properties, and water has
diffused into the coating.
Figure 7 shows the Rp as a function of time for NC0,
NC1, NC3 and NC5 samples, determined by fitting the
EIS data with electrical equivalent circuits shown in Fig. 5,
and obtained from 0 to 2000 immersion hours. At the
beginning, the Rp of NC0, NC1, NC3 and NC5 nanocom-
posite coatings as determined by EIS data fitting was 45,
91, 100 and 54 GΩ cm2
, respectively (Figure 7(a)). These
results show that addition of nanoparticles improve the
coatings resistance. During this exposure time, Rp values
of NC3 are higher than Rp of the reference sample NC0.
Although the values of Rp varied for more than one order
of magnitude for different nanocomposite coatings during
the first 850 hours of exposure to a corrosive agent, after
this exposure time differences among nanocomposite coat-
ings were smaller and are constant after this period. How-
ever, the Rp values for NC3 remained significantly higher
as compared to the Rp value for NC0 throughout the
whole investigated time. After 850 h, the Rp values of
Figure 4. TGA thermograms of OMMT, NC0, NC1, NC3 and NC5 obtained under
nitrogen atmosphere.
Table 1. TGA results for NC0, NC1, NC3 and NC5 nanocomposites.
Sample Clay loadings (wt-%) IDT(°C) Residual mass (%)
NC0 0 366.95 17.5
NC1 1 347.37 17.7
NC3 3 346.13 19.54
NC5 5 273.66 19.54
Figure 5. EEC for the studied coating systems.
CORROSION ENGINEERING, SCIENCE AND TECHNOLOGY 365

6. nanocomposite coatings decrease slowly, which can be
explained by plugging of the pores among clay particles
with corrosion products, which is a clear evidence of the
organoclay barrier effect.
Regarding to the coating capacitance values, it has been
reported a three-stage behaviour. A rapid initial increase
due to homogeneous water uptake, followed by a saturation
plateau and, finally, a rapid increase as more water is accu-
mulated heterogeneously in the coating [44–47] or under-
neath the coating [48]. In our case, no-one of the coatings
followed exactly the described trend (Figure 7(b)). In the
case of NC5 sample (containing 5 wt-% montmorillonite),
the capacitance values increased at the initial stages of
immersion, then oscillate probably due to corrosion of the
steel or delamination of the coating [47], instead of saturat-
ing. This is consistent with the results from visual
examination of the exposed panels, which showed evident
corrosion spot and delamination.
In the case of other three coatings included in this study,
the capacitance values increased slightly in the beginning of
the test and then were retained at a constant value, but the
final increase was not detected. Hence, these coatings are
probably under saturation with water. Overall, the highest
coating capacitance values were obtained for NC5, where
the amount of OMMT was 5 wt-%, suggesting higher degree
of water uptake than, for example, epoxy coating. In turn, the
lowest coating capacitance values were obtained for sample
NC3, indicating a lower water absorption than in the case
of epoxy coating, consistent with visual examination of the
exposed panels.
Table 2 shows variations of RCT and Cdl after 850 immer-
sion hours. The loss RCT for the NC3 sample is 1 order of
Figure 6. EIS spectra for NC0, NC1, NC3 and NC5 coatings on the steel substrate. (a) Bode diagram at initial immersion; (b) Bode diagram after 350 h of immersion; (c)
Bode diagram after 700 h of immersion; (d) Bode diagram after 850 h of immersion.
Table 2. Variations of RCT and Cdl parameters after 850 immersion hours.
Sample 850 h 1250 h 1500 h 2000 h
RCT: charge transfer resistance (Ω cm2
)
NC0 8.95*109
1.17*108
4.73*107
5.73*106
NC1 3.93*109
2.12*109
3.16*108
3.97*107
NC3 3.95*1011
4.15*109
1.32*109
1.51*1010
NC5 1.54*108
5.33*106
1.83*107
2.71*105
Cdl: double-layer capacitance (F cm−2
)
NC0 5.09*10−9
1.22*10−8
7.8*10−9
3.5*10−8
NC1 4.69*10−9
5.93*10−9
6.4*10−9
1.51*10−8
NC3 1.56*10−9
2.92*10−9
3.98*−9
5.27*10−9
NC5 1.42*10−8
3.29*10−8
2.13*10−8
1.72*10−6
366 J. L. VARELA CASELIS ET AL.

7. magnitude while the NC0 sample has 3 orders of magnitude
of loss. Also, Cdl for the NC3 sample not show increase but
the NC0 sample shows 1 order of magnitude increase.
These results may be explained by a possible occupying by
the organoclay of the free volume, i.e. voids and defects,
which are preferential diffusion paths for water molecules,
ions and oxygen, the penetration of which through the coat-
ing is a prerequisite for corrosion of the substrate to occur
[44,49], these events decreases corrosion as could be observed
in Figure 8 where less damage is observed for the NC3
sample. It may also be expected that the organoclay block
not only the diffusion paths through the coating but also
those in the horizontal direction, i.e. between local anodes
and cathodes along the coating/substrate interface. This is,
however, dependent on the nanoparticle orientation.
RCT for NC5 sample (with 5 wt-% OMMT) was the lowest
during the test, this behaviour may be due to low chemical
stability of the coating, as a result of an incomplete curing
reaction (this is confirmed by FTIR spectrum of Figure 3),
which caused less crosslinking of the polymer matrix and
therefore greater degradation facilitating the increase of pre-
ferential routes of diffusion of corrosive species towards the
metal-coating interface, which accelerates the corrosion pro-
cess as can be seen in Figure 8 where more damage is
observed for the NC5 sample.
Figure 8 shows the coatings images after immersion testing
in a solution of sodium chloride 5 wt-%. After exposure of the
samples for 850 h, a brown adherent corrosion product
(which is a mixture of iron hydroxides) was observed over
the samples surface. Delamination and water penetration
were observed around the scratches which decreased in the
order of NC5 > NC1 > NC0 > NC3. Immersion tests indicate
that the least corroded sample was NC3. This result reveals
that montmorillonite may be used to improve corrosion pro-
tection properties of the UV-cured Araldite 506 epoxy
coating.
Figure 7. Evolution of electrical network parameters for the studied coatings. (a) Resistance (Rp); (b) Capacitance (Cc).
CORROSION ENGINEERING, SCIENCE AND TECHNOLOGY 367

8. Conclusions
SEM analysis showed that epoxy-OMMT coatings uniform
and free of defects were obtained on a corrodible surface as
carbon steel and that OMMT was homogenous dispersed in
the polymer matrix. By means of the XRD analysis, it was ver-
ified that the polymer was intercalated in the OMMT struc-
ture. Additionally, it was confirmed that the amine group
containing the OMMT affects the UV curing of the Araldite
506 resin, as evidenced by FTIR spectra.
Electrochemical impedance measurements at various
exposure periods, indicated that NC3 coating on cold rolled
mild steel coupons showed better anticorrosive properties in
5 wt-% NaCl solution than NC0, NC1 and NC5 coatings. The
NC3 coating provided improved corrosion protection even
after 850 h of exposure to NaCl solution. EIS results agree the
visual evaluation test, which showed that the NC3 coating has
better resistance to corrosion for carbon steel than the others
coatings. This study shows that the addition of an organoclay
such as OMMT, improves the anticorrosive properties of a
UV-cured DGBA epoxy resin, in this case, Araldite 506.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by Vicerrectoría de Investigación y Estudios de
Posgrado of the Benemérita Universidad Autónoma de Puebla, México.
ORCID
M. Sánchez Cantú http://orcid.org/0000-0003-2044-893X
O. Olivares Xometl http://orcid.org/0000-0003-0525-6155
M. Morales Sánchez http://orcid.org/0000-0002-2361-9645
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