RAJESWARAN M. et al.: INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG ...
521–529
INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL
BEHAVIOURS OF CUPOLA SLAG AND MWCNT-REINFORCED
EPOXY HYBRID NANOCOMPOSITES: A SUSTAINABLE
APPROACH FOR ENVIRONMENTAL PRESERVATION
DOLO^ITEV TRIBOLO[KIH IN MEHANSKIH LASTNOSTI
HIBRIDNEGA KOMPOZITA SESTAVLJENEGA IZ KUPOLNE
@LINDRE IN VE^-STENSKIH OGLJIKOVIH NANOCEVK:
PRIJAZNI IN TRAJNOSTNI PRISTOP VAROVANJA OKOLJA
Rajeswaran M.
1
, Prathap P.
1*
, Kannan S.
2
, Sundaravadivel T. A.
3
1
Department of Mechanical Engineering, Sri Krishna College of Technology, Coimbatore, Tamil Nadu 641042, India
2
Department of Mechanical Engineering, Hindusthan College of Engineering and Technology, Coimbatore, Tamil Nadu 641032, India
3
Department of Mechanical Engineering, R M D Engineering College, Chennai, Tamil Nadu 601206, India
Prejem rokopisa – received: 2024-04-30; sprejem za objavo – accepted for publication: 2024-07-04
doi:10.17222/mit.2024.1179
This experimental investigation explores the mechanical and tribological characteristics of cupola slag (CS) and multiwall car-
bon nanotubes (MWCNTs) reinforced hybrid nanofiller epoxy composites. Cupola slag is an industrial by-product that is gener-
ated during the melting of cast iron. The disposal of slag residues in landfills results in environmental pollution. In the context
of environmental preserving as well developing new engineering composites material from waste to resource. MWCNTs possess
an excellent strength-to-weight ratio, high stiffness, and thermal properties. The mechanical and tribological characteristics of
the hybrid nanocomposites comprising epoxy were examined by varying the weight fraction of fillers composed of CS and
MWCNTs. The experimental results indicated that the ECSM3 hybrid nanocomposites have superior tensile strength and the
flexural modulus improved by 92 % and 78 % respectively when compared with epoxy. Similarly, the tribology performance of
the ECSM3 exhibited improved specific wear resistance of 97 %, 106 % and 88 % on the dry-sliding loads of 10 N, 20 N and
30N, respectively. A morphological analysis was carried out on fractured and worn surfaces of the specimen to understand the
homogeneous dispersion and matrix-interlocking mechanism between the hybrid nanofillers and the epoxy matrix. The integra-
tion of CS alongside MWCNTs for the fabrication of epoxy hybrid nanocomposites represents a stride towards sustainable and
eco-friendly technology in the production of multifunctional composite materials for diverse engineering applications.
Keywords: tribology, wear, cupola slag, mwcnts, epoxy, hybrid, nanocomposites
V ~lanku avtorji opisujejo eksperimentalno raziskavo mehanskih in tribolo{kih lastnosti hibridnega epoksidnega kompozita z
oja~itvijo iz delcev kupolne `lindre (CS; angl.: cupola slag) in ve~stenskih ogljikovih nano cev~ic (MWCNTs; angl.: multiwall
carbon nanotubes). Kupolna `lindra je stranski produkt, ki nastaja med proizvodnjo sive litine. Odlaganje ostankov kupolne
`lindre na raznih odlagalnih poljih predstavlja velik okoljski problem. Zato raziskovalci poizku{ajo najti oziroma razviti nove
in`enirske kompozitne materiale, ki vsebujejo dolo~en dele` te vrste odpadkov. Po drugi strani imajo MWCNTs odli~no
mehansko trdnost in trdoto, odli~no razmerje med trdnostjo in specifi~no masno gostoto, veliko togost in dobre termi~ne
lastnosti. Izdelanim hibridnim kompozitom z epoksidno osnovo in razli~nimi masnimi dele`i dodanih MWCNTs in CS so
avtorji dolo~ili mehanske in tribolo{ke lastnosti. Rezultati mehanskih preiskav ECSM3 (3 % CS in 0,3 % MWCNTs) hibridnih
kompozitov so pokazali, da imajo le-ti odli~no natezno trnost in upogibni modul v primerjavi z epoksidno smolo. Natezna
trdnost ECSM3 se je pove~ala z dodatkoma za 92 % in upogibni modul se je izbolj{al za 78 %. Podobno se je odpornost proti
drsni obrabi tega hibridnega kompozita izbolj{ala za 97 % pri obremenitvi 10 N, za 106 % pri obremenitvi 20N in za 88 % pri
obremenitvi 30 N. Izvr{ena morfolo{ka analiza je na prelomih preizku{ancev in na drsno obrabljenih povr{inah preizku{ancev
pokazala, da imajo izdelani kompoziti homogeno dispergirane delce MWCNTs in CS v epoksidni matrici. Ti so dobro
medsebojno mehansko povezani z izbrano polimerno matrico. Integracija kupolne `lindre in ve~ stenskih ogljikovih nano cev~ic
v epoksidno smolo predstavlja pomemben napredek v smeri trajne in ekolo{ke tehnologije izdelave ve~funkcionalnih
kompozitnih materialov za razli~ne in`enirske aplikacije.
Klju~ne besede: tribologija, obraba, kupolna `lindra (CS), ve~stenske ogljikove nano cev~ice (MWCNTs), epoksidna smola,
hibridni nanokompoziti
1 INTRODUCTION
Industrial solid waste, comprising various by-prod-
ucts and residues from manufacturing processes, poses a
significant environmental challenge when disposed of in
landfills. Such waste materials frequently encompass
harmful elements like heavy metals, hazardous chemi-
cals, and materials that do not decompose naturally.
These substances have the potential to seep into the soil
and underground water, leading to the pollution of
nearby ecosystems and presenting environmental haz-
ards. To reduce these adverse effects, it is imperative to
prioritize sustainable waste-management approaches, in-
cluding recycling, composting, waste-to-energy conver-
Materiali in tehnologije / Materials and technology 58 (2024) 4, 521–529 521
UDK 543.632.542 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 58(4)521(2024)
*Corresponding author's e-mail:
prathu135@gmail.com (Prathap P.)

sion, and the adoption of innovative reuse methods.
These initiatives aim to decrease the quantity of waste
destined for landfills, while simultaneously fostering re-
source conservation and preventing pollution. Effective
waste-management practices are essential for attaining
optimal reuse outcomes. Cupola slag is a by-product of
cast-iron production, characterized by its high silica con-
tent and diverse chemical composition. It is commonly
generated in cupola slag during the melting of metal
scrap and iron ore. The primary disposal method for cu-
pola slag is landfilling, wherein the slag is buried in des-
ignated areas. However, the practice of landfilling can re-
sult in detrimental environmental consequences such as
the contamination of soil and groundwater, air pollution,
and disruption of habitats. This underscores the urgency
of implementing sustainable waste-management solu-
tions. Epoxy resins are widely recognized for their re-
markable mechanical strength, resistance to chemicals,
and adhesive properties, making them essential in the
realm of polymer composite production. These thermo-
setting polymers, characterized by a complex three-di-
mensional network, demonstrate exceptional dimen-
sional stability and minimal shrinkage upon curing.
1
Their capacity to adhere to various substrates and un-
dergo customizable formulations renders them indispens-
able in composite manufacturing processes.
2
Addi-
tionally, epoxy resins offer tailored mechanical and
thermal characteristics, contributing to the superior per-
formance of polymer composites in diverse applications,
ranging from aerospace to automotive.
3
Their versatile
nature allows for the production of lightweight, durable,
and high-performance composite materials tailored to
specific engineering requirements. Multiwall carbon
nanotubes (MWCNTs) exhibit outstanding mechanical,
electrical, and thermal characteristics, making them in-
dispensable in various polymer-composite applications.
Their high aspect ratio, extraordinary tensile strength,
and superior conductivity make them ideal candidates for
enhancing the mechanical and electrical properties of
polymer matrices.
4
Furthermore, MWCNTs exhibit ex-
cellent chemical stability and resistance to environmental
degradation, ensuring the longevity and durability of
composite materials.
5
Their ability to form strong inter-
facial interactions with polymer matrices enhances the
load transfer and dispersion, leading to improved me-
chanical reinforcement and electrical conductivity in
polymer composites.
6
As a result, MWCNTs are pivotal
in enhancing the performance and functionality of poly-
mer composites across diverse industrial sectors.
7
The in-
corporation of carbon nanotubes (CNTs) in fly-ash-based
geopolymer composites has been shown to enhance their
mechanical properties, thereby improving the strength
and durability of these composites for construction appli-
cations.
8
The incorporation of fly ash into polyester com-
posites is to enhance their mechanical and thermal prop-
erties.
9
Optimizing the filler size and dispersion of fly
ash is crucial for improving the mechanical properties of
epoxy-based composites. This optimization aims to en-
hance the structural properties of the composites by
investigating the influence of fly-ash particle size on
their mechanical behavior.
10
Evaluating the mechanical
properties of epoxy composites containing fly-ash parti-
cles aims to determine the viability of utilizing fly ash as
an economical filler material in epoxy-matrix compos-
ites.
11
Thermal conductivity and mechanical properties of
fly-ash/epoxy composites through the incorporation of
functionalized graphene nanoplatelets (GNPs) to develop
high-performance composites for thermal management
applications.
12
The enhancement of mechanical proper-
ties in blast furnace slag-based polymer composites by
incorporating carbon nanotubes (CNTs) to enhance the
composites for structural applications.
13
The thermal
conductivity enhancement of foundry sand-filled epoxy
composites using boron nitride (BN) nanoparticles to en-
hance the heat-transfer properties of the composites for
thermal management applications.
14
The structural and
temperature characteristics of polypropylene composites
filled with electronic waste to evaluate the feasibility of
utilizing E-waste as a filler material in polymer compos-
ites for various engineering applications.
15
The study
provides insights into sustainable approaches for recy-
cling waste and reducing environmental impact in com-
posite manufacturing.
16
The environmental sustainability
of waste-derived polymer composites assesses the
lifecycle impacts and environmental benefits of utilizing
waste materials in composite manufacturing, highlight-
ing the importance of sustainable materials’ development
for mitigating environmental concerns.
17
The research
outlined on leveraging cupola slag to enhance the me-
chanical and environmental properties of polymer com-
posites, contributing to sustainable materials develop-
ment. Incorporating recycled waste and industrial
by-products into construction materials is now essential
to preserve natural resources and address waste-disposal
environmental issues
18
.
In this research work, epoxy-matrix composites rein-
forced by CS-MWCNTs hybrid nanofillers, in which the
CNTs are dispersed homogeneously and at the same time
strongly attached with the CS nanofillers. CNTs exhibit-
ing high tensile strength, low density, high aspect ratio
and rigidity, superior electrical and thermal conductivity
are widely used for structural applications. Combining
CNTs with cupola slag may ensure the following advan-
tages. First, CNTs effectively attached on the surface of
the CS which will lead to easy dispersion during the
sonication process and eliminate the agglomeration in
the host matrix. Second, both CS and CNT particles have
mechanical characteristics and their hybridization may
improve the tribological properties. Third, CNTs surface
tangle on the CS particle can make surface interlocks and
thus enhance the epoxy/hybrid nanofiller interface phe-
nomenon.
RAJESWARAN M. et al.: INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG ...
522 Materiali in tehnologije / Materials and technology 58 (2024) 4, 521–529

2 MATERIALS AND METHODS
2.1 Materials
The epoxy Diglycidyl Ether of Bisphenol A
(DGEBA) was used in this study, while the curing agent
selected was HTDA (4-methylcyclohexane-1,3-diamine),
with a ratio of 10:1. The density of procured epoxy is
1200 kg/m
3
. The MWCNTs external diameter of
30–40 nm and a length of 4–5 μm with purity greater
than 95 %. Both the materials were purchased from
Bottomup Technologies, Bangalore, India. The raw form
of cupola slag collected from Bakgiyam Engineering –
Iron Casting Foundry, Coimbatore, India. The slag was
taken into various desizing and cleaning process for
composites preparation process.
2.2 Production of nano dimension cupola slag
High-energy ball milling was used to achieve nano-
scale dimensions of cupola slag. Utilizing a high-energy
ball milling setup, the slag particles are subjected to me-
chanical forces generated by the collision of milling
balls. The process parameters, including milling balls
with the diameter of 10 mm and the canister were made
of carbon steel. The ball to powder ratio is 10:1 in
weight. After completion of5ho fmilling process, the
machine shutdown for 0.5 h to cool the canister. During
milling the 200 min
–1
speed is set to constant for 8h with
5:1 as ball to powder ratio is to be maintained for effi-
cient size reduction. The repetitive impact and grinding
action gradually reduce the particle size of the slag.
Moreover, the selection of ball material is pivotal to in-
fluencing the efficacy of the milling process. Through
careful control of the milling conditions, the cupola slag
is progressively transformed into nano-sized particles in
the range 150 nm ± 20 nm, exhibiting enhanced reactiv-
ity and surface area. Figure 1a shows the SEM images
of milled cupola slag. This methodology enables the pro-
duction of nanostructured cupola slag, offering promis-
ing prospects for its utilization in various advanced mate-
rials and engineering applications. The chemical
components of the cupola slag are listed in Table 1.
2.3 Synthesis of MWCNTs
The carbon nanotubes (CNTs) utilized in this investi-
gation were produced via thermal decomposition of hy-
drocarbon gas using chemical vapor deposition (CVD) as
shown in Figure 1b. Benzene served as the source of
carbon, thiophene as a growth catalyst, ferrocene as the
catalyst, and hydrogen as the carrier gas. The proportions
of these components in the reaction system were ad-
justed by controlling the flow rate of the carrier gas. By
manipulating the reaction duration and the relative
amounts of benzene, thiophene, and ferrocene, carbon
nanotubes and carbon nanofibers with diverse diameters
and structures were synthesized.
2.4 Preparation of CS-CNTs epoxy nanocomposites
The dispersion of CS-MWCNTs in the epoxy resin
Diglycidyl Ether of Bisphenol A was achieved by means
of a sonicator machine operating at a frequency of
30 kHz for a duration of 20 min. To lower the viscosity
of the epoxy and to enable better wetting of the particle
during the sonication process the temperature was main-
tained between 70 °C and 80 °C. The MWCNTs in their
initial state taken into purification and functionalization
through heat treatment, resulting in the introduction of
carboxylic acid groups. This process involved immersing
1 g of MWCNTs in a solution consisting of 500 mL of
H
2
SO
4
and HNO
3
in a volume ratio of 3:2, followed by
RAJESWARAN M. et al.: INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG ...
Materiali in tehnologije / Materials and technology 58 (2024) 4, 521–529 523
Figure 1: FESEM images of a) cupola slag and b) MWCNTs used in this experiment
Table 1: Cupola slag chemical composition in weight fraction
Chemical composition w/%
Silicon 49.7
Iron oxide 17.9
Alumina 10.9
Calcium oxide 11.1
Manganese oxide 3.41
Magnesium oxide 2.04
Titanium dioxide 1.39
Potassium oxide 0.98

ultrasonic treatment for 12 h at ambient temperature to
prepare a suspension. Subsequently, the prepared solu-
tion is heated at 80 °C and stirred for 18 h before under-
going filtration through a nylon membrane. The
MWCNTs, after filtration, experienced extensive wash-
ing with water, repeating the process to attain a neutral
pH. The treatment with HNO
3
resulted in functional-
ization of the MWCNTs surface without significantly af-
fecting their length. The MWCNTs were dried in a vac-
uum chamber at ambient conditions for 24 h. The second
filler material, cupola slag (CS) is in a size range a little
bigger than the MWCNTs. The particles are irregular
ball shaped and the specific area was also considerably
large. The cupola slag consisted of silicon oxide layers
that hold strongly together. The cupola-slag surface was
treated with carboxylic acid groups. An ultrasonicator
was used to disperse the CS in the SOCl
2
and the stirring
process continued for 5 h under ambient conditions. Fur-
thermore, the suspension was filter dried for 18 hours at
ambient temperature.
For the fabrication of the CS-MWCNTs epoxy nano-
composites, the procedure commenced with the addition
of designated weight fractions of MWCNTs and cupola
slag (CS) (Table 2) fillers into an ethanol solvent, fol-
lowed by continuous stirring for 15 min. Subsequently,
polyvinylpyrrolidone (PVP) dispersant was introduced
and stirred for an additional 10 min. Next, preheated ep-
oxy was incorporated into the solution and sonicated for
2 h to achieve a homogeneous distribution of the fillers
within the matrix. To eliminate the solvents, the suspen-
sion was kept at 100 °C in an oil container for 3 h. Upon
cooling to room temperature, the corresponding curing
agent was added, and sonication continued for another 5
min. For tribological and mechanical characterization,
the solution was poured into designed acrylic moulds to
manufacture the test specimens as per the standards.
Subsequently, all test specimens are cured at room tem-
perature for 12 h, followed by maintenance at 50°C for
18 h for post-curing. The designated weight fraction of
cupola slag and MWCNTs with various weight fractions
is presented in Table 2 and the composites sample were
analysed by X-ray diffractometer (XRD).
2.5 Characterization techniques
Microstructure characterizations of the
CS-MWCNTs nano fillers and composites fracture sur-
face and worn surface were examine by field-emission
scanning electron microscope (FESEM) and X-ray
diffractometer (XRD) (Figure 2a and 2b). The aim was
to understand the influence of nanofillers on the reinforc-
ing mechanism and wear mechanism.
2.6 Mechanical characterization
Tensile examinations of epoxy resin and
CS-MWCNTs filler-reinforced hybrid epoxy composites
were performed utilizing a universal tensile test appara-
tus (Instron, USA) in accordance with ASTM D-638
standards. Specimens were shaped into dumbbell config-
urations for assessment purposes. The varying lengths of
the specimens were measured by an extensometer at a
crosshead movement speed of 1 mm/min. To ensure sta-
tistical robustness, five specimens were utilized to derive
the mean value and recorded. In accordance with ASTM
D7264 guidelines, flexural characteristics were per-
formed on epoxy and CS-MWCNTs filler-reinforced hy-
brid epoxy composites. The samples were shaped into
rectangular dimensions measuring (60 × 13 × 4) mm
3
.
The crosshead movement of the jaw set to 1 mm/min to
measure the displacement rate. The test specimen both
the ends knurled for excellent gripping actions. Each test
was repeated five times to ensure statistical accuracy, al-
RAJESWARAN M. et al.: INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG ...
524 Materiali in tehnologije / Materials and technology 58 (2024) 4, 521–529
Figure 2: XRD pattern and SEM images of CS-MWCNTs hybrid nanocomposites
Table 2: Description and label of MWCNTs and cupola slag weight
fraction
Sample Description Label
Epoxy + Cupola slag 1.0 w/% + MWNCTs 0.1 w/% ECSM1
Epoxy + Cupola slag 2.0 w/% + MWNCTs 0.2 w/% ECSM2
Epoxy + Cupola slag 3.0 w/% + MWNCTs 0.3 w/% ECSM3
Epoxy + Cupola slag 4.0 w/% + MWNCTs 0.4 w/% ECSM4
Epoxy + Cupola slag 5.0 w/% + MWNCTs 0.5 w/% ECSM5

lowing for the calculation of the mean value and stan-
dard deviation.
2.7 Tribology characterization
Dry-sliding wear tests were carried out on a
pin-on-disc machine to determine the tribological char-
acteristics of the epoxy and epoxy-hybrid nanocom-
posites. A rotating counterpart was made up of a com-
mercially available steel disc (EN8) with a surface
roughness of Ra = 0.6 μm, hardness 60 HRc and diame-
ter of 100 mm. The test specimen held against the
high-speed rotating counterpart with the radius of
25 mm, rotating speed of 250 min
–1
and running in pe-
riod and distance of 1000 m and 0.5 h, respectively. Dur-
ing this test, the sample was under 10 N (low), 20 N
(moderate), and 30 N (high) loads against the steel disc
counterpart. During the wear process the material re-
move from the sample which leads to mass reduction oc-
curred on the sample specimen. The mass reduction was
estimated by measuring the material removed from the
test specimen before and after the wear test. The specific
wear rate, which demonstrate the wear characteristics
under the predetermined condition for the tribosystem
from the calculated value.
w
m
Fn L
s
=
⋅⋅
Δ
 (mm
3
/Nm) (1)
where w
s
= specific wear rate, m = change in the mass
of the wear test specimen (g),  = density of the com-
posites (g/cm
3
), Fn = Load acting on the specimen and
L = distance of sliding (m).
3 RESULT AND DISCUSSION
3.1 Mechanical characteristics
3.1.1 Tensile characteristics
Epoxy and CS-MWCNTs with various weight frac-
tion of filler loading hybrid nanocomposites tensile
stress-strain typical curve is presented in Figure 3. Inter-
estingly, nanofiller reinforced epoxy hybrid composites
exhibit an improvement of the tensile characteristics
compared to the epoxy. It can be shown that the epoxy
hybrid nanocomposites exhibit higher tensile strength
and higher flexural modulus compared to the epoxy. The
ECSM3 composites exhibit the highest tensile strength,
achieving an increase of approximately 94.3 MPa, corre-
sponding to a 92 % enhancement compared to the pure
epoxy. Similarly, ECSM4 also exhibits an increase in
tensile strength as compared to epoxy matrix but lower
than ECSM3 about 70 % and 31 %, respectively. The
matrix material strength, fillers particle shape and size,
interfacial adhesion and homogeneous dispersion in the
matrix are significant parameters in the tensile strength
of polymer composites materials. In our formulation, the
RAJESWARAN M. et al.: INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG ...
Materiali in tehnologije / Materials and technology 58 (2024) 4, 521–529 525
Figure 4: Tensile strength of epoxy and the epoxy-hybrid nanocom-
posites with various weight fractions
Figure 3: Stress–strain curve for epoxy and the epoxy-hybrid nanocomposites with various weight fractions

CS-MWCNTs reinforced epoxy demonstrates an en-
hancement in tensile strength when contrasted with pure
epoxy. The cupola slag serves as a conduit for the disper-
sion of CNTs into the matrix, while concurrently facili-
tating the formation of CNT networks instead of agglom-
eration. These networks effectively absorb the applied
tensile loads from the matrix during loading.
However, a further increase of filler content of the
pure epoxy on 0.4 w/% and 0.5 w/% of MWCNTs and
4 w/% and 5 w/% of cupola slag decreasing trend of ten-
sile strength as shown in Figure 4. This occurrence is
anticipated and primarily attributed to the agglomeration
of CNTs, particularly at higher filler loadings, exacer-
bated by the substantial surface area of the CNTs. The
weak van der Waals’ forces between the CNTs lead to
their interconnection, resulting in agglomeration. There-
fore, the strength and modulus of the composites can
serve as indicators for pre-evaluating the extent of filler
dispersion within the composite materials.
The impacts and significance of a substantial en-
hancement in tensile strength, the fractured surface of
the nanofillers reinforced epoxy composites were ana-
lysed using FESEM, as shown in Figure 5. The mor-
phology analysis found that the epoxy fractured surface
exhibits hyperbolic opening and nuclei tearing. This will
indicate the material fracture occurred with a brittle na-
ture. Further, ECSM1 and ECSM2 fracture surface ex-
hibits micro cracks, pore, rupture and plasticity surface
on the fracture surface, which indicates the material
tends from brittle to ductile in nature. Similarly, the
ECSM3 hybrid composites fracture morphology shown
larger smoother surface, CS-MWCNTs interlocking re-
veals material tends to elongate during the fracture,
which means materials tends to be ductile in nature. Fur-
thermore, ECSM4 and ECSM5 fractured surface demon-
strated macro crack, slip and brittle marking and fillers
pull out exhibits reform of the material ductile to brittle
in nature, as well the nonuniform distribution of fillers
tends to local failure within the matrix, which leads the
composites to fail and transfer the load by the filler.
3.1.2 Flexural modulus
The significant improvement achieved in stress-strain
behaviour of the nanofiller-loaded epoxy-hybrid nano-
composites due to the filler natural characteristics as well
the optimum level of incorporation in the host matrix.
Well-known materials science revealed that when the
filler content exceeds the optimum level this leads to
lower performance of the matrix properties. Surprisingly,
the flexural modulus results are in incremental value
with respect to increasing the filler loading, which means
that the flexural modulus value increase linearly until the
filler content reaches the optimum level, as shown in
Figure 6. Certain critical attributes of the composites
must be considered to describe this phenomenon. The in-
terface between filler and matrix is inadequate, the parti-
cles fail to bear any portion of the external load. Conse-
quently, the strength of the composite cannot surpass that
of the pure polymer matrix. In contrast, when the bond-
ing between fillers and matrix is sufficiently robust, the
yield strength of a particulate composite can exceed that
RAJESWARAN M. et al.: INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG ...
526 Materiali in tehnologije / Materials and technology 58 (2024) 4, 521–529
Figure 5: SEM morphology analysis of epoxy and CS-MWCNTs hybrid nanocomposites fractured surface
Figure 6: Flexural modulus of epoxy and the epoxy-hybrid nanocom-
posites with various weight fractions

of the matrix polymer. The morphology analysis ex-
plores the conclusions regarding the dissipation of en-
ergy during fracture, understanding the path of traveling
cracks through the material and the influence of particles
on crack propagation is crucial, as shown in Figure 7.
Cracks interact with particles as obstacles, potentially al-
tering the crack front by deviation or branching, or even
pinning it, thereby necessitating increased energy ab-
sorption in the composite. Additionally, significant en-
ergy may be expended at the interface between particles
and matrix, particularly under conditions of strong bond-
ing. The interface explores a significance in the deforma-
tion behavior of the composite materials.
3.2 Tribological characteristics
The tribological systems of epoxy and nanofiller-re-
inforced epoxy-hybrid nanocomposites were described
with wear and friction characteristics. The sample mate-
rial, rotating counterpart and ambient conations are the
important functional parts of the tribology system. To at-
tain the constant level of the frictional force and coeffi-
cient, the specimen has taken into initial running time
period to attain the steady-state level. The temperature
between the test sample and counterparts is not to exceed
45 °C during the entire process of the wear-test experi-
ments. This present study was to explore the influence of
cupola slag and MWCNTs nano particle in the epoxy
matrix. In the previous literature it is found that small
particles exhibit good wear resistance, and it can shield
the polymer surface and restrict the filler pull outs. The
pin-on-disc machine was used for conducting the wear
experiments. The experiment results plotted in Figure 8.
The specific wear resistance is plotted as a function of
various filler compositions. A high resistance to wear
phenomena on the material means a decrease in wear
rate. The improvement in the specific wear resistance of
the CS-MWCNTs nano-filler-loaded epoxy nano com-
posites observed on ECSM1 and ECSM2 composition
compared with epoxy. Furthermore, ECSM3 composi-
tion demonstrated remarkable specific wear resistance
and recorded 97 %, 106 %, 88 % higher than the epoxy
matrix on the dry-sliding load of 10 N, 20 N and 30 N,
respectively. Similarly, increasing the filler content, the
specific wear resistance considerably decreased for the
ECSM4 and ECSM 5 composites. Interestingly, it is ob-
served that the ECSM 4 wear resistance was higher than
the epoxy, but lower than the ECSM 3 composites. The
phenomena reveals that the matrix reached the saturation
level of the optimized level of weight fraction. Further-
more, increasing the filler content, i.e., ECSM 5 deterio-
ration of wear behaviour and the wear resistance lower
than the epoxy matrix.
RAJESWARAN M. et al.: INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG ...
Materiali in tehnologije / Materials and technology 58 (2024) 4, 521–529 527
Figure 8: specific wear rate of epoxy and the epoxy hybrid nanocomposites with various weight fraction
Figure 7: SEM morphology analysis of epoxy, ECSM3 and ECSM5 hybrid nanocomposites flexural fractured surface

The morphological analysis was carried out on the
worn surface of the epoxy and CS-MWCNTs nano-
filler-loaded hybrid nanocomposites to understand the
material removal phenomena. The worn surface and its
wear pattens are presented in Figure 9. The epoxy worn
surface exhibits crack opening, hyperbolic marking and
step fracture occurred on the surface. Furthermore,
ECSM1 and ECSM2 shown microcrack, scars, limited
smooth surface reveal that the wear mechanism trans-
form from brittle to ductile in nature. Similarly, ECSM3
worn surface showed a smooth and even surface. In addi-
tion, ECSM4 and ECSM5 worn surfaces exhibit chevron
marking, pit, macro crack, surface irregularity, delami-
nation, filler putouts and larger pit presented on higher
and excessive additions of nano fillers in the matrix,
which leads lower the performance of composites. Inter-
esting observation reveals that, under lower load (10 N)
and moderate loading (20 N) and higher loading (30 N)
conditions, the wear rate also gradually increased in all
the compositions, which clearly indicates that the wear
rate increased with an increase of the applied load due to
an increase in contact pressure, which leads to an in-
crease in temperature. Furthermore, an increase in tem-
perature is softening the contact surface, which leads to
filler pull outs. As noted earlier, the optimum weight
fraction added into the matrix leas to robust improve-
ment in the wear resistance.
4 CONCLUSIONS
The aim of developing a multifunctional hybrid
nanocomposites material from industrial waste to re-
source has been achieved in this investigation. The ep-
oxy-hybrid nanocomposites have been fabricated with
the reinforcement of cupola slag and MWCNTs for the
investigation of tribological and mechanical characteris-
tics. Foundry industries dispose of the cupola slag
through landfill, which leads to environmental pollution.
Thus, developing these kinds of nanocomposites materi-
als for multifunctional engineering applications helps to
preserve the environment.
The research aims to explore the mechanical and
tribological properties of epoxy composites reinforced
with cupola slag (CS) and multiwall carbon nanotubes
(MWCNTs), addressing environmental concerns associ-
ated with CS disposal.
Cupola slag, an industrial byproduct from cast-iron
melting, is highlighted as a material of interest due to its
abundance and environmental impact caused by landfill
disposal.
The study underscores the dual purpose of environ-
mental preservation and resource utilization by trans-
forming waste materials, such as CS, into valuable engi-
neering composites.
MWCNTs, renowned for their exceptional strength-
to-weight ratio, high stiffness, and thermal properties,
are utilized to enhance the mechanical performance of
the composites.
Investigation of varying weight fractions of
CS-MWCNTs fillers allows for the assessment of me-
chanical and tribological characteristics in the epoxy-hy-
brid nanocomposites.
Experimental findings reveal significant enhance-
ments in the properties of ECSM3 hybrid nanocom-
posites, with a remarkable 92 % increase in tensile
strength and a 78 % improvement in flexural modulus
compared to pure epoxy.
Tribological assessments demonstrate notable im-
provements in specific wear resistance, with ECSM3 ex-
hibiting enhancements of 97 %, 106 % and 88 % under
dry-sliding loads of 10 N, 20 N, and 30 N, respectively.
Morphological analysis provides insights into the dis-
persion and interlocking mechanisms between hybrid
RAJESWARAN M. et al.: INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG ...
528 Materiali in tehnologije / Materials and technology 58 (2024) 4, 521–529
Figure 9: SEM morphology analysis of epoxy and CS-MWCNTs hybrid nanocomposites worn surface

nanofillers and the epoxy matrix, elucidating the struc-
tural integrity of the composites.
The integration of CS and MWCNTs represents a
stride towards sustainable and eco-friendly composite
material fabrication, offering multifunctional solutions
for diverse engineering applications.
5 REFERENCES
1
A. Curt, NM Epoxy Handbook’, 3
rd
ed., Nils Malmgren AB, Sweden
2004
2
J. Parameswaranpillai, N. Hameed, J. Pionteck, Woo, E. (eds), Hand-
book of Epoxy Blends, Springer, 2017, doi:10.1007/978-3-319-
40043-3_14
3
L. Guadagno, L. Vertuccio, A. Sorrentino, M. Raimondo, C. Naddeo,
V. Vittoria, G. Iannuzzo, E. Calvi, S. Russo, Mechanical and barrier
properties of epoxy resin filled with multi-walled carbon nanotubes,
Carbon, 47 (2009) 10, 2419–2430, doi:10.1016/j.carbon.2009.04.035
4
T. Shen, Y. Chen, W. Liu, J. Ma, S. Yang, Y. Wang, G. Wang, Prepa-
ration and properties of carbon nanotube/polymer composites, J.
Appl. Polym. Sci., 135 (2018) 11, 89–98, doi:10.1016/j.compositesa.
2018.02.030
5
Garima Mittal, Vivek Dhand, Kyong Yop Rhee, Soo-Jin Park, Wi Ro
Lee, A review on carbon nanotubes and graphene as fillers in rein-
forced polymer nanocomposites, J. Ind. Eng. Che., 21 (2015), 11–25,
doi:10.1016/j.jiec.2014.03.022
6
J. Xu, Aihong Kang, Z. Wu, P. Xiao, Y. Gong, Effect of high-calcium
basalt fiber on the workability, mechanical properties and micro-
structure of slag-fly ash geopolymer grouting material, Constr. Build.
Mater., 302 (2021), 124089, doi:10.1016/j.conbuildmat.2021.
124089
7
K. R. Kumar, K. M. Mohanasundaram, G. Arumaikkannu, R.
Subramanian, Effect of particle size on mechanical properties and
tribological behaviour of aluminium/fly ash composites, Sci. Eng.
Compos. Mater., 19 (2012) 3, 247–253, doi:10.1515/secm-2011-
0139
8
H. X. Peng, Z. Fan, D. Z. Wang, In situ Al3Ti-Al2O3 intermetallic
matrix composite: synthesis, microstructure, and compressive behav-
ior, J. Mater. Res., 15 (2000) 9, 1943–1949, doi:10.1557/JMR.2000.
0280.
9
N. Sombatsompop, S. Thongsang, T. Markpin, E. Wimolmala, Fly
ash particles and precipitated silica as fillers in rubbers. I. Untreated
fillers in natural rubber and styrene-butadiene rubber compounds, J.
Appl. Polym. Sci., 93 (2004), 2119–2130, doi:10.1002/app.20693
10
S. M. Kulkarni, Kishore, Effect of filler-fiber interactions on com-
pressive strength of fly ash and short-fiber epoxy composites, J.
Appl. Polym. Sci., 87 (2003), 836–841, doi:10.1002/app.11501
11
V. K. Srivastava, P. S. Shembekar, R. Prakash, Fracture behaviour of
fly-ash filled FRP composites, Compos. Struct., 10 (1988)4 ,
271–279, doi: 10.1016/0263-8223(88)90006-2
12
Kishore, S. M. Kulkarni, S. Sharathchandra, D. Sunil, On the use of
an instrumented set-up to characterize the impact behaviour of an ep-
oxy system containing varying fly ash content, Polym. Test., 21
(2002), 763–771, doi:10.1016/S0142-9418(02)00008-9
13
W. Tang, G. Pignatta S. M. E. Sepasgozar, Life-cycle assessment of
fly ash and cenosphere-based geopolymer material, Sustainability, 12
(2021), 11167, doi:10.3390/su132011167
14
R. Yang, Effect of multi-pass friction stir processing on micro-
structure and mechanical properties of Al3Ti/A356 composites, Ma-
ter. Char., 106 (2015) 62–69, doi:10.1016/j.matchar.2015.05.019
15
J. Ladomerský, I. Janotka, E. Hroncová, I. Najdená, One-year prop-
erties of concrete with partial substitution of natural aggregate by cu-
pola foundry slag, J. Clean. Prod. 131 (2016) 739–746, doi:10.1016/
j.jclepro.2016.04.101
16
V. K. Mistry, D. J. Varia, Green concrete by replacing coarse aggre-
gate with cupola slag for environmental protection, Smart Innov.
Syst. Technol. 161 (2020) 223–237, doi:10.1007/978-981-32-
9578-0-20
17
A. Pribulova, D. Baricova, P. Futas, M. Pokusova, S. Eperjesi, Cu-
pola furnace slag: its origin, properties and utilization, Int. J. Med. 13
(2019) 3, 627–640, doi:10.1007/s40962-019-00314-3
18
N. S. Shiny, G. Brintha, Utilization of slag powder and recycled con-
crete wastes in reactive powder concrete, MatTech 57(2023)2 ,
103–109, doi:10.17222/mit.2022.701
RAJESWARAN M. et al.: INVESTIGATION OF THE MECHANICAL AND TRIBOLOGICAL BEHAVIOURS OF CUPOLA SLAG ...
Materiali in tehnologije / Materials and technology 58 (2024) 4, 521–529 529