Performance analysis of recycled PET composites reinforced with waste slate dust: physico-mechanical and wear properties
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About This Presentation
In this study, thermoplastic composites were developed from recycled poly(ethylene terephthalate) (rPET) reinforced with waste slate dust (WSD). The composites were processed through twin-screw extrusion followed by injection moulding with varying WSD contents (0–20 wt%). The fabricated composites...
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Research Article
Received: 3 August 2025 Revised: 14 September 2025 Published online in Wiley Online Library:
(wileyonlinelibrary.com) DOI 10.1002/pi.70043
PerformanceanalysisofrecycledPET
compositesreinforcedwithwasteslatedust:
physicomechanicalandwearproperties
Aditya Chauhan,
a
Robert Brüll,
b*
Subrajeet Deshmukh,
b
Sampat Singh Bhati,
a
Kirtiraj K Gaikwad
a*
and Tej Singh
c
Abstract
In this study, thermoplastic composites were developed from recycled poly(ethylene terephthalate) (rPET) reinforced with
waste slate dust (WSD). The composites were processed through twin-screw extrusion followed by injection molding with vary-
ing WSD contents (0–20 wt%). The fabricated composites were systematically characterized for their physical, mechanical, slid-
ing wear and morphological properties. The composites exhibited a monotonic increase in Young's modulus from 2.14 to
3.00 GPa andflexural modulus from 2.11 to 3.20 GPa. Flexural strength increased modestly from 72.5 to 76.8 MPa, while the
tensile strength remained largely unaffected (38.07 MPa for neat rPETversus37.27 MPa at 20 wt% WSD). In contrast, the elon-
gation at break was reduced byca36% at 5 wt% andca80% at 20 wt%, and impact strength dropped from 19.6 to 10.0 kJ m
−2
.
Surface hardness increased slightly (76.1 to 78.0), while wear performance improved significantly, with the specific wear rate
decreasing by more than 60% at 20 wt% WSD. Thesefindings show the potential of repurposing slate waste as a functionalfiller
for rPET-based composites, thus providing the dual benefit of performance enhancement and circular material utilization.
© 2025 Society of Chemical Industry.
Keywords:recycled poly(ethylene terephthalate); slate dust; polymer composites; mechanical properties; wear resistance; waste
valorization
INTRODUCTION
The accumulation of solid waste has become one of the most
pressing environmental challenges of the 21st century, with plas-
tics as dominant contributor.
1
Global plastic production now
exceeds 380 million tonnes annually, yet only about 9% is effec-
tively recycled. The remainder is either incinerated or landfilled,
causing significant ecological and resource concerns.
2,3
Poly(ethylene terephthalate) (PET) is among the most widely used
thermoplastics, following polyolefins and polystyrene.
4
It has a
semicrystalline structure with high toughness, mechanical
strength, chemical resistance and transparency.
5
These properties
make PET highly adaptable for a wide range of applications,
including food packaging, syntheticfibers, beverage bottles, cas-
settes and engineering components.
6,7
However, PET waste is
often mismanaged and generates 8% by weight and 12% by vol-
ume of total solid waste worldwide.
8
Therefore, recycling PET is
essential to mitigate environmental impact and conserve energy
since recycled PET (rPET) requires 50–60% less energy than virgin
PET production.
9–11
Recycling approaches for PET include thermal (energy recov-
ery), biochemical or catalytic depolymerization (to regenerate
monomers) and mechanical reprocessing.
12
Among these,
mechanical recycling is the most industrially viable due to its
lower energy demands and established large-scale infrastruc-
ture.
13
PET recycling starts with sorting and separating the waste,
followed by washing to remove any impurities. The clean PET is
then shredded and ground intoflakes or powder, which is further
re-extruded to produce granules for making new products.
14
However, recycling of PET is challenging, as reprocessing often
leads to the deterioration of its mechanical and chemical proper-
ties due to hydrolytic and thermomechanical degradation.
15,16
This involves chain scission and a reduction in PET molecular
weight.
17
To maintain the properties of the recyclates, most of
the time, additives (copolymers, antioxidants,filler particles, chain
extenders, etc.) are introduced to the material during the proces-
sing stage.
18,19
These additives can enhance the material through
various mechanisms, enabling the recyclate to perform at a level
comparable to or exceeding that of the virgin polymer.
20
*Correspondence to: KK Gaikwad, Department of Paper and Packaging Tech-
nology, Indian Institute of Technology Roorkee, Roorkee, 247667, India.
E-mail:[email protected]; or R Brüll, Department Material Analysis
and Characterization, Division Plastics, Fraunhofer Institute for Structural,
Durability and System Reliability LBF, 64289 Darmstadt, Germany.
E-mail:[email protected]
aDepartment of Paper and Packaging Technology, Indian Institute of Technol-
ogy Roorkee, Roorkee, India
bDepartment Material Analysis and Characterization, Division Plastics, Fraun-
hofer Institute for Structural Durability and System Reliability LBF, Darmstadt,
Germany
cSavaria Institute of Technology, Faculty of Informatics, ELTE Eötvös Loránd
University, Budapest, Hungary
Polym Int2025 www.soci.org © 2025 Society of Chemical Industry.
1
Received: 3 August 2025 Revised: 14 September 2025 Published online in Wiley Online Library:
(wileyonlinelibrary.com) DOI 10.1002/pi.70043
PerformanceanalysisofrecycledPET
compositesreinforcedwithwasteslatedust:
physicomechanicalandwearproperties
Aditya Chauhan,
a
Robert Brüll,
b*
Subrajeet Deshmukh,
b
Sampat Singh Bhati,
a
Kirtiraj K Gaikwad
a*
and Tej Singh
c
Abstract
In this study, thermoplastic composites were developed from recycled poly(ethylene terephthalate) (rPET) reinforced with
waste slate dust (WSD). The composites were processed through twin-screw extrusion followed by injection molding with vary-
ing WSD contents (0–20 wt%). The fabricated composites were systematically characterized for their physical, mechanical, slid-
ing wear and morphological properties. The composites exhibited a monotonic increase in Young's modulus from 2.14 to
3.00 GPa andflexural modulus from 2.11 to 3.20 GPa. Flexural strength increased modestly from 72.5 to 76.8 MPa, while the
tensile strength remained largely unaffected (38.07 MPa for neat rPETversus37.27 MPa at 20 wt% WSD). In contrast, the elon-
gation at break was reduced byca36% at 5 wt% andca80% at 20 wt%, and impact strength dropped from 19.6 to 10.0 kJ m
−2
.
Surface hardness increased slightly (76.1 to 78.0), while wear performance improved significantly, with the specific wear rate
decreasing by more than 60% at 20 wt% WSD. Thesefindings show the potential of repurposing slate waste as a functionalfiller
for rPET-based composites, thus providing the dual benefit of performance enhancement and circular material utilization.
© 2025 Society of Chemical Industry.
Keywords:recycled poly(ethylene terephthalate); slate dust; polymer composites; mechanical properties; wear resistance; waste
valorization
INTRODUCTION
The accumulation of solid waste has become one of the most
pressing environmental challenges of the 21st century, with plas-
tics as dominant contributor.
1
Global plastic production now
exceeds 380 million tonnes annually, yet only about 9% is effec-
tively recycled. The remainder is either incinerated or landfilled,
causing significant ecological and resource concerns.
2,3
Poly(ethylene terephthalate) (PET) is among the most widely used
thermoplastics, following polyolefins and polystyrene.
4
It has a
semicrystalline structure with high toughness, mechanical
strength, chemical resistance and transparency.
5
These properties
make PET highly adaptable for a wide range of applications,
including food packaging, syntheticfibers, beverage bottles, cas-
settes and engineering components.
6,7
However, PET waste is
often mismanaged and generates 8% by weight and 12% by vol-
ume of total solid waste worldwide.
8
Therefore, recycling PET is
essential to mitigate environmental impact and conserve energy
since recycled PET (rPET) requires 50–60% less energy than virgin
PET production.
9–11
Recycling approaches for PET include thermal (energy recov-
ery), biochemical or catalytic depolymerization (to regenerate
monomers) and mechanical reprocessing.
12
Among these,
mechanical recycling is the most industrially viable due to its
lower energy demands and established large-scale infrastruc-
ture.
13
PET recycling starts with sorting and separating the waste,
followed by washing to remove any impurities. The clean PET is
then shredded and ground intoflakes or powder, which is further
re-extruded to produce granules for making new products.
14
However, recycling of PET is challenging, as reprocessing often
leads to the deterioration of its mechanical and chemical proper-
ties due to hydrolytic and thermomechanical degradation.
15,16
This involves chain scission and a reduction in PET molecular
weight.
17
To maintain the properties of the recyclates, most of
the time, additives (copolymers, antioxidants,filler particles, chain
extenders, etc.) are introduced to the material during the proces-
sing stage.
18,19
These additives can enhance the material through
various mechanisms, enabling the recyclate to perform at a level
comparable to or exceeding that of the virgin polymer.
20
*Correspondence to: KK Gaikwad, Department of Paper and Packaging Tech-
nology, Indian Institute of Technology Roorkee, Roorkee, 247667, India.
E-mail:[email protected]; or R Brüll, Department Material Analysis
and Characterization, Division Plastics, Fraunhofer Institute for Structural,
Durability and System Reliability LBF, 64289 Darmstadt, Germany.
E-mail:[email protected]
aDepartment of Paper and Packaging Technology, Indian Institute of Technol-
ogy Roorkee, Roorkee, India
bDepartment Material Analysis and Characterization, Division Plastics, Fraun-
hofer Institute for Structural Durability and System Reliability LBF, Darmstadt,
Germany
cSavaria Institute of Technology, Faculty of Informatics, ELTE Eötvös Loránd
University, Budapest, Hungary
Polym Int2025 www.soci.org © 2025 Society of Chemical Industry.
1
Parallel to the plastic industry, the construction and mining sec-
tors also face waste management difficulties.
21
For instance, slate
used for construction applications such as roofing, control boards,
blackboards and electrical insulation
22,23
generates enormous
amounts of leftovers during extraction, cutting and polishing.
24
Literature indicates that producing 1 t of useful slate product may generate as much as 30 t of waste, mainly in the form of dust and chips.
25
If not properly managed, thesefine dust particles can
pose health and environmental risks. Slate deposits are geologi-
cally heterogeneous, and their mineral composition varies by
source. This typically includes quartz, phyllosilicates, illite and
oxides of Si, Al and Fe.
24,26
Waste slate dust (WSD) is characterized
by its irregular particle morphology, high compressive strength
and relatively low bulk density, that makes it a viable candidate
for reinforcing thermoplastic matrices.
27
Additionally, due to its
natural color variations (ranging from black to grey and blue), it
can also serve as a colorant in polymers.
28
Recent advances in sustainable materials engineering have
accelarated the use of industrial byproducts as reinforcement in
polymer composites, supporting the transition from linear to cir-
cular resource models.
29
Moreover, the environmental advan-
tages are greater when both the polymer matrix and thefiller
material are obtained from waste streams. WSD comprises many
conventionalfiller components that are used to produce plastic
components across a range of industries.
30
In addition to its favor-
able composition, powdered material is easier to incorporate into
thermoplastic and thermoset matrices thanfibers. This, in turn,
enhances the mechanical, thermal and tribological properties of
the resulting composites.
31
Several studies have explored the effect of slate in polymers.
Samperet al.
23
reported that the incorporation of waste slate
fibers into an epoxidized linseed oil matrix significantly enhanced
the mechanical properties of the composite, including tensile
strength, tensile modulus,flexural strength and impact resistance.
De Carvalhoet al.
28
fabricated slate-reinforced polypropylene
composites using varying WSD loadings. Their results showed
that the incorporation of WSD maintained equivalent tensile
strength even at 10 wt%filler content. Notably, the composites
containing 5 and 10 wt% slate exhibited optical properties com-
parable to those of commercial slate. Quiles-Carrilloet al.
32
devel-
oped and investigated the effect of slatefiber in polyamide 1010.
They reported a threefold increase in tensile modulus for ther-
mally treated and silane-modified slatefibers. Additionally, the
composites exhibited higher tensile strength, Shore D hardness
and resistance to moisture-induced degradation. Carbonell-Verdú
et al.
25
prepared composites with high-density polyethylene rein-
forced with silane-treated slatefibers. Notable improvements
were observed in tensile (19.5 to 22.6 MPa) andflexural (26.8 to
31.7 MPa) strengths. This enhancement was attributed to better
fiber–matrix adhesion and uniform dispersion of thefibers.
Recently, Khanet al.
22,30
investigated WSD reinforcement in
poly(lactic acid) and acrylonitrile–butadiene–styrene. They com-
pounded the materials using an extruder and used an FDM 3D
printer to produce test specimens. Theirfindings indicate that
adding WSD steadily increased the hardness and modulus of both
polymers. However, it led to a reduction in elongation at break.
Interestingly, tensile andflexural strengths improved with WSD
content of 5–10 wt%. Beyond that, no further improvements were
observed.
The aforementioned research indicates that adding slate based
materials can improve the physical, mechanical and thermal prop-
erties of a polymer. Although a range of mineralfillers like talc,
33
marble dust,
29
CaCO
3,
34
sepiolite
35,36
and halloysite nanotubes
37
have been examined in rPET systems. There is no study based
on the influence of WSD as afiller on rPET behavior. Therefore,
the study reported here addressed the gap by examining the
incorporation of 0–20 wt% WSD into rPET and evaluating its
impact on mechanical, morphological and tribological perfor-
mance. The research presents new and insightful viewpoints on
recycling slate waste and suggests a unique approach for inte-
grating it into plastic industries.
EXPERIMENTAL
Materials
The rPET was used as a matrix for the composite, which was
obtained from Südpack GmbH & Co. KG (Ochsenhausen,
Germany). It was supplied as green granules derived from post
consumer food packaging trays andfilms. The material density
was 1.33 g cm
−3
with an intrinsic viscosity of 0.52 dL g
−1
. WSD,
having a grey color and a density of 2.51 g cm
−3
, was acquired
from Vincenzo Solutions Pvt. Ltd (Jaipur, India). Fig.
1presents
the morphological and compositional features of WSD. The SEM
micrograph (Fig.
1(a)) shows irregular particle morphologies,
while the particle size distribution (Fig.1(b)) indicates that most
particles were in the 5–20μm range. The energy-dispersive
X-ray spectroscopy (EDS) spectrum (Fig.1(c)) confirms the pres-
ence of O, Si, Al, Fe, K, Mg and Ti, corresponding to the oxides
SiO
2,Al
2O
3,Fe
2O
3,K
2O, MgO and TiO
2.
23
Material preparation and processing
The supplied rPET granules were ground with an ultra-centrifugal
mill (Retsch ZM 200, Haan, Germany) at 18 000 rpm using a
1.5 mm screen. Generally, ground polymer facilitates better mix-
ing withfiller particles and improves processability.
38
The rPET
and WSD were premixed in a container to reduce segregation
during feeding. This was followed by drying in an oven (Thermo
Fisher Scientific, USA) at 120°C to minimize moisture-induced
degradation during melt processing
15,39
because rPET is suscepti-
ble to hydrolytic degradation at elevated temperatures. The oven
was equipped with a degassing unit and was maintained at
50 mbar throughout the drying period. The material was then
vacuum-sealed in multilayer bags to prevent environmental
exposure and was only opened just before processing. Mixing
WSD at 0 to 20 wt% with rPET resulted infive different composi-
tions, as detailed in Table
1. The selectedfiller levels were
intended to include both low-load and high-load conditions, con-
sistent with the ranges typically examined forfilled
thermoplastics.
6,40
Melt compounding was performed with a co-rotating twin-
screw extruder (Thermo Scientific Process 11, Fisher Scientific).
The extruder was equipped with an 11 mm barrel, eight individu-
ally heated zones (including the nozzle) and a maximum screw
speed of 1000 rpm. The premixed rPET/WSD blends were fed
through a top-mounted hopper, and compounding was carried
out at a feed rate of 10 rpm with a screw speed of 100 rpm. The
barrel temperature profile was set to 240°C (feeder) and gradu-
ally increased to 260°C at the nozzle. At this stage, the strong
shear and kneading action of the co-rotating screws enabled
the even dispersion of WSD particles within the rPET matrix. The
pressure was maintained between 320 and 355 mbar throughout
the extrusion period using a degassing unit. The extrudedfila-
ment was cooled in a water bath and then passed through an
air-drying unit. Finally, thefilament was converted into granules
www.soci.org A Chauhan et al.
wileyonlinelibrary.com/journal/pi © 2025 Society of Chemical Industry. Polym Int2025
2 10970126, 0, Downloaded from https://scijournals.onlinelibrary.wiley.com/doi/10.1002/pi.70043 by POLITECNICO DI MILANO, Wiley Online Library on [16/10/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
tors also face waste management difficulties.
21
For instance, slate
used for construction applications such as roofing, control boards,
blackboards and electrical insulation
22,23
generates enormous
amounts of leftovers during extraction, cutting and polishing.
24
Literature indicates that producing 1 t of useful slate product may generate as much as 30 t of waste, mainly in the form of dust and chips.
25
If not properly managed, thesefine dust particles can
pose health and environmental risks. Slate deposits are geologi-
cally heterogeneous, and their mineral composition varies by
source. This typically includes quartz, phyllosilicates, illite and
oxides of Si, Al and Fe.
24,26
Waste slate dust (WSD) is characterized
by its irregular particle morphology, high compressive strength
and relatively low bulk density, that makes it a viable candidate
for reinforcing thermoplastic matrices.
27
Additionally, due to its
natural color variations (ranging from black to grey and blue), it
can also serve as a colorant in polymers.
28
Recent advances in sustainable materials engineering have
accelarated the use of industrial byproducts as reinforcement in
polymer composites, supporting the transition from linear to cir-
cular resource models.
29
Moreover, the environmental advan-
tages are greater when both the polymer matrix and thefiller
material are obtained from waste streams. WSD comprises many
conventionalfiller components that are used to produce plastic
components across a range of industries.
30
In addition to its favor-
able composition, powdered material is easier to incorporate into
thermoplastic and thermoset matrices thanfibers. This, in turn,
enhances the mechanical, thermal and tribological properties of
the resulting composites.
31
Several studies have explored the effect of slate in polymers.
Samperet al.
23
reported that the incorporation of waste slate
fibers into an epoxidized linseed oil matrix significantly enhanced
the mechanical properties of the composite, including tensile
strength, tensile modulus,flexural strength and impact resistance.
De Carvalhoet al.
28
fabricated slate-reinforced polypropylene
composites using varying WSD loadings. Their results showed
that the incorporation of WSD maintained equivalent tensile
strength even at 10 wt%filler content. Notably, the composites
containing 5 and 10 wt% slate exhibited optical properties com-
parable to those of commercial slate. Quiles-Carrilloet al.
32
devel-
oped and investigated the effect of slatefiber in polyamide 1010.
They reported a threefold increase in tensile modulus for ther-
mally treated and silane-modified slatefibers. Additionally, the
composites exhibited higher tensile strength, Shore D hardness
and resistance to moisture-induced degradation. Carbonell-Verdú
et al.
25
prepared composites with high-density polyethylene rein-
forced with silane-treated slatefibers. Notable improvements
were observed in tensile (19.5 to 22.6 MPa) andflexural (26.8 to
31.7 MPa) strengths. This enhancement was attributed to better
fiber–matrix adhesion and uniform dispersion of thefibers.
Recently, Khanet al.
22,30
investigated WSD reinforcement in
poly(lactic acid) and acrylonitrile–butadiene–styrene. They com-
pounded the materials using an extruder and used an FDM 3D
printer to produce test specimens. Theirfindings indicate that
adding WSD steadily increased the hardness and modulus of both
polymers. However, it led to a reduction in elongation at break.
Interestingly, tensile andflexural strengths improved with WSD
content of 5–10 wt%. Beyond that, no further improvements were
observed.
The aforementioned research indicates that adding slate based
materials can improve the physical, mechanical and thermal prop-
erties of a polymer. Although a range of mineralfillers like talc,
33
marble dust,
29
CaCO
3,
34
sepiolite
35,36
and halloysite nanotubes
37
have been examined in rPET systems. There is no study based
on the influence of WSD as afiller on rPET behavior. Therefore,
the study reported here addressed the gap by examining the
incorporation of 0–20 wt% WSD into rPET and evaluating its
impact on mechanical, morphological and tribological perfor-
mance. The research presents new and insightful viewpoints on
recycling slate waste and suggests a unique approach for inte-
grating it into plastic industries.
EXPERIMENTAL
Materials
The rPET was used as a matrix for the composite, which was
obtained from Südpack GmbH & Co. KG (Ochsenhausen,
Germany). It was supplied as green granules derived from post
consumer food packaging trays andfilms. The material density
was 1.33 g cm
−3
with an intrinsic viscosity of 0.52 dL g
−1
. WSD,
having a grey color and a density of 2.51 g cm
−3
, was acquired
from Vincenzo Solutions Pvt. Ltd (Jaipur, India). Fig.
1presents
the morphological and compositional features of WSD. The SEM
micrograph (Fig.
1(a)) shows irregular particle morphologies,
while the particle size distribution (Fig.1(b)) indicates that most
particles were in the 5–20μm range. The energy-dispersive
X-ray spectroscopy (EDS) spectrum (Fig.1(c)) confirms the pres-
ence of O, Si, Al, Fe, K, Mg and Ti, corresponding to the oxides
SiO
2,Al
2O
3,Fe
2O
3,K
2O, MgO and TiO
2.
23
Material preparation and processing
The supplied rPET granules were ground with an ultra-centrifugal
mill (Retsch ZM 200, Haan, Germany) at 18 000 rpm using a
1.5 mm screen. Generally, ground polymer facilitates better mix-
ing withfiller particles and improves processability.
38
The rPET
and WSD were premixed in a container to reduce segregation
during feeding. This was followed by drying in an oven (Thermo
Fisher Scientific, USA) at 120°C to minimize moisture-induced
degradation during melt processing
15,39
because rPET is suscepti-
ble to hydrolytic degradation at elevated temperatures. The oven
was equipped with a degassing unit and was maintained at
50 mbar throughout the drying period. The material was then
vacuum-sealed in multilayer bags to prevent environmental
exposure and was only opened just before processing. Mixing
WSD at 0 to 20 wt% with rPET resulted infive different composi-
tions, as detailed in Table
1. The selectedfiller levels were
intended to include both low-load and high-load conditions, con-
sistent with the ranges typically examined forfilled
thermoplastics.
6,40
Melt compounding was performed with a co-rotating twin-
screw extruder (Thermo Scientific Process 11, Fisher Scientific).
The extruder was equipped with an 11 mm barrel, eight individu-
ally heated zones (including the nozzle) and a maximum screw
speed of 1000 rpm. The premixed rPET/WSD blends were fed
through a top-mounted hopper, and compounding was carried
out at a feed rate of 10 rpm with a screw speed of 100 rpm. The
barrel temperature profile was set to 240°C (feeder) and gradu-
ally increased to 260°C at the nozzle. At this stage, the strong
shear and kneading action of the co-rotating screws enabled
the even dispersion of WSD particles within the rPET matrix. The
pressure was maintained between 320 and 355 mbar throughout
the extrusion period using a degassing unit. The extrudedfila-
ment was cooled in a water bath and then passed through an
air-drying unit. Finally, thefilament was converted into granules
www.soci.org A Chauhan et al.
wileyonlinelibrary.com/journal/pi © 2025 Society of Chemical Industry. Polym Int2025
2 10970126, 0, Downloaded from https://scijournals.onlinelibrary.wiley.com/doi/10.1002/pi.70043 by POLITECNICO DI MILANO, Wiley Online Library on [16/10/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
with a pelletizer (Jiading, China). Fig.2presents a schematic lay-
out of the twin-screw extrusion setup and the corresponding tem-
perature profile applied during compounding.
The prepared granules were dried again at 120°C and 50 mbar
for 8 h. Injection molding was performed on a laboratory scale
Babyplast 6/10P unit (Christmann Kunststofftechnik GmbH,
Germany). The processing temperature of the barrel was 250–
260°C (feeder to the nozzle), while the mold temperature was
60°C. One specimen was produced per cycle using two mold cav-
ities: dog-bone (Type 5A) and rectangular bar (70×10×4mm
3
).
Fig.
3presents an image of the prepared specimens for tensile
testing.
CHARACTERIZATION TECHNIQUES
SEM (MIRA 3 LMH, Tescan, USA) was used to capture magnified
images of the sample surface. One sample from each of the
rPET/WSD compositions was taken at a time for SEM analysis. Ele-
mental composition was analyzed using an EDS detector (Oxford
Instruments) attached to the SEM system. To avoid surface charg-
ing, all samples were sputter-coated with a thin layer of gold for
180 s using an automaticfine coater (JEOL JFC 1600, Tokyo,
Japan). An accelerating voltage of 15 kV was used to record the
elemental data. The experimental density of the composites was
determined at ambient temperature (25°C) using Archimedes'
principle (standard water displacement method). Theoretical den-
sity was calculated via the rule of mixtures. Meanwhile, the void
content of the composites was determined by normalizing the
Figure 1.(a) SEM micrograph, (b) particle size distribution (image analysis,N=55) and (c) EDS spectrum of WSD.
Table 1.Sample designation and weight composition of the pre-
pared composites
Sample designation rPET (wt%) WSD (wt%)
rPET 100 0
rPET_2.5WSD 97.5 2.5
rPET_5WSD 95 5
rPET_10WSD 90 10
rPET_20WSD 80 20
Performance analysis of recycled PET composites reinforced with waste slate dust: physicomechanical and wear properties www.
soci.org
Polym Int2025 © 2025 Society of Chemical Industry. wileyonlinelibrary.com/journal/pi
3 10970126, 0, Downloaded from https://scijournals.onlinelibrary.wiley.com/doi/10.1002/pi.70043 by POLITECNICO DI MILANO, Wiley Online Library on [16/10/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
out of the twin-screw extrusion setup and the corresponding tem-
perature profile applied during compounding.
The prepared granules were dried again at 120°C and 50 mbar
for 8 h. Injection molding was performed on a laboratory scale
Babyplast 6/10P unit (Christmann Kunststofftechnik GmbH,
Germany). The processing temperature of the barrel was 250–
260°C (feeder to the nozzle), while the mold temperature was
60°C. One specimen was produced per cycle using two mold cav-
ities: dog-bone (Type 5A) and rectangular bar (70×10×4mm
3
).
Fig.
3presents an image of the prepared specimens for tensile
testing.
CHARACTERIZATION TECHNIQUES
SEM (MIRA 3 LMH, Tescan, USA) was used to capture magnified
images of the sample surface. One sample from each of the
rPET/WSD compositions was taken at a time for SEM analysis. Ele-
mental composition was analyzed using an EDS detector (Oxford
Instruments) attached to the SEM system. To avoid surface charg-
ing, all samples were sputter-coated with a thin layer of gold for
180 s using an automaticfine coater (JEOL JFC 1600, Tokyo,
Japan). An accelerating voltage of 15 kV was used to record the
elemental data. The experimental density of the composites was
determined at ambient temperature (25°C) using Archimedes'
principle (standard water displacement method). Theoretical den-
sity was calculated via the rule of mixtures. Meanwhile, the void
content of the composites was determined by normalizing the
Figure 1.(a) SEM micrograph, (b) particle size distribution (image analysis,N=55) and (c) EDS spectrum of WSD.
Table 1.Sample designation and weight composition of the pre-
pared composites
Sample designation rPET (wt%) WSD (wt%)
rPET 100 0
rPET_2.5WSD 97.5 2.5
rPET_5WSD 95 5
rPET_10WSD 90 10
rPET_20WSD 80 20
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disparity between theoretical and experimental densities against
the theoretical density.
Tensile testing is a fundamental material science test and
involves controlled tension on a sample until it breaks. Using a
ZwickiLine Z2.5 (Zwick-Roell, Ulm, Germany) outfitted with
a 2.5 kN load cell, the tensile tests were carried out. The dog-bone
specimens had an initial cross-section of 4×2mm
2
and a gauge
length of 55 mm. Young's modulus was calculated at a
1 mm min
−1
crosshead rate. In contrast, yield and breakage data
were analyzed at 2 mm min
−1
by DIN EN ISO 527-1:2019-2112
standard.
Flexural testing (static three-point bending) was performed
using a ZwickiLine Z5flexural tester (Zwick-Roell, Ulm, Germany)
attached to a 5 kN load cell by DIN EN ISO 178:2019-2108 require-
ments, a standard forflexural testing. The measurements were
taken at a span of 64 mm using rectangular specimens with a
cross-section size of 10×4mm
2
. The tensile andflexural samples
were tested at standard climate (23±2°C, 50±10% RH). The
data were recorded and evaluated using test Xpert II software.
Shore D surface hardness was measured using a PCE-DD-D
Durometer in accordance with ISO 868 standards. To ensure suffi-
cient thickness, three identical tensile specimens were stacked
during measurements. Shore D hardness is the relative hardness
of rigid materials, such as rigid plastics and their composites,
where a higher value on the scale indicates better indentation
resistance. The Izod impact resistance of prepared composite
specimens was measured by EN ISO 180 standard, using a Tinius
Olsen impact tester (Impact 104) equipped with a 2 J pendulum.
Unnotched rectangular bars of 10×4mm
2
cross-section were
used at a gripping length of 62 mm.
Sliding wear tests were performed on neat rPET and rPET/WSD
composites using a computer-controlled pin-on-disc (TR-20 LE,
DUCOM, India) type tribo-test rig. The counterface was a horizon-
tally rotating grey cast-iron disc, 165 mm in diameter. It had a Bri-
nell hardness of 179–229 HB and a surface roughness of
R
a=0.6μm. All experiments were conducted with a
20×4×4mm
3
sample size under ambient conditions. The load
applied was 30 N, with a sliding velocity of 4 m s
−1
. The wear track
diameter was 120 mm, and the sliding distance remained con-
stant at 1500 m. The weight of the sample was measured before
and after the wear test using an electronic balance from Wensar
Weighing Scales Ltd, India. The wear was calculated in terms of
the specific wear rate using Eqn (
1)
41,42
:
Specific wear rate=
Wi−Wf
L×ρ
exp×D
cm
3
N
−1
m
−1
fifl
ð1Þ
whereW
i=initial weight of the sample (g);W f=final weight of
the sample (g);L=applied load (N),ρ
exp=experimental density
of sample (g cm
−3
);D=sliding distance (m).
The results were assessed using one-way analysis of variance
and afterwards analyzed withpost hocTukey tests at a signifi-
cance level of 5% (P<0.05).
RESULTS AND DISCUSSIONS
Surface morphology
SEM was used to assess the dispersion, interfacial bonding and
surface characteristics of WSD particles embedded within the
rPET matrix. The images (Fig.
4(b)–(e)) show the dispersed phase
(slate domains) integrated into the polymer matrix, except for
Fig.
4(a), which does not contain WSDfiller particles. The EDS
Figure 2.Schematic of twin-screw extruder setup used for melt compounding.
Figure 3.Prepared specimens for tensile testing.
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the theoretical density.
Tensile testing is a fundamental material science test and
involves controlled tension on a sample until it breaks. Using a
ZwickiLine Z2.5 (Zwick-Roell, Ulm, Germany) outfitted with
a 2.5 kN load cell, the tensile tests were carried out. The dog-bone
specimens had an initial cross-section of 4×2mm
2
and a gauge
length of 55 mm. Young's modulus was calculated at a
1 mm min
−1
crosshead rate. In contrast, yield and breakage data
were analyzed at 2 mm min
−1
by DIN EN ISO 527-1:2019-2112
standard.
Flexural testing (static three-point bending) was performed
using a ZwickiLine Z5flexural tester (Zwick-Roell, Ulm, Germany)
attached to a 5 kN load cell by DIN EN ISO 178:2019-2108 require-
ments, a standard forflexural testing. The measurements were
taken at a span of 64 mm using rectangular specimens with a
cross-section size of 10×4mm
2
. The tensile andflexural samples
were tested at standard climate (23±2°C, 50±10% RH). The
data were recorded and evaluated using test Xpert II software.
Shore D surface hardness was measured using a PCE-DD-D
Durometer in accordance with ISO 868 standards. To ensure suffi-
cient thickness, three identical tensile specimens were stacked
during measurements. Shore D hardness is the relative hardness
of rigid materials, such as rigid plastics and their composites,
where a higher value on the scale indicates better indentation
resistance. The Izod impact resistance of prepared composite
specimens was measured by EN ISO 180 standard, using a Tinius
Olsen impact tester (Impact 104) equipped with a 2 J pendulum.
Unnotched rectangular bars of 10×4mm
2
cross-section were
used at a gripping length of 62 mm.
Sliding wear tests were performed on neat rPET and rPET/WSD
composites using a computer-controlled pin-on-disc (TR-20 LE,
DUCOM, India) type tribo-test rig. The counterface was a horizon-
tally rotating grey cast-iron disc, 165 mm in diameter. It had a Bri-
nell hardness of 179–229 HB and a surface roughness of
R
a=0.6μm. All experiments were conducted with a
20×4×4mm
3
sample size under ambient conditions. The load
applied was 30 N, with a sliding velocity of 4 m s
−1
. The wear track
diameter was 120 mm, and the sliding distance remained con-
stant at 1500 m. The weight of the sample was measured before
and after the wear test using an electronic balance from Wensar
Weighing Scales Ltd, India. The wear was calculated in terms of
the specific wear rate using Eqn (
1)
41,42
:
Specific wear rate=
Wi−Wf
L×ρ
exp×D
cm
3
N
−1
m
−1
fifl
ð1Þ
whereW
i=initial weight of the sample (g);W f=final weight of
the sample (g);L=applied load (N),ρ
exp=experimental density
of sample (g cm
−3
);D=sliding distance (m).
The results were assessed using one-way analysis of variance
and afterwards analyzed withpost hocTukey tests at a signifi-
cance level of 5% (P<0.05).
RESULTS AND DISCUSSIONS
Surface morphology
SEM was used to assess the dispersion, interfacial bonding and
surface characteristics of WSD particles embedded within the
rPET matrix. The images (Fig.
4(b)–(e)) show the dispersed phase
(slate domains) integrated into the polymer matrix, except for
Fig.
4(a), which does not contain WSDfiller particles. The EDS
Figure 2.Schematic of twin-screw extruder setup used for melt compounding.
Figure 3.Prepared specimens for tensile testing.
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results (Fig.4(g)–(j)) further validated these speculations by dem-
onstrating that the primary constituting elements, such as Si (cor-
responding to SiO
2), Al (corresponding to Al
2O
3) and Fe
(corresponding to Fe
2O
3), of slate are found in the matrix. Addi-
tionally, the amount of these elements increased with higherfiller
loadings, confirming progressive incorporation of WSD particles
into the matrix. Importantly, the noticeable unlisted peak atca
2.2 keV in the EDS spectrum is due to the presence of coated gold
on the composites. It can be seen in Fig.
4(b)that rPET_2.5WSD
has a relatively smooth surface as compared to higher WSD-
Figure 4.SEM images of the injection-molded surface of (a) neat rPET, (b) rPET_2.5WSD, (c) rPET_5WSD, (d) rPET_10WSD and (e) rPET_20WSD; and cor-
responding EDS spectra of (f) neat rPET, (g) rPET_2.5WSD, (h) rPET_5WSD, (i) rPET_10WSD and (j) rPET_20WSD.
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onstrating that the primary constituting elements, such as Si (cor-
responding to SiO
2), Al (corresponding to Al
2O
3) and Fe
(corresponding to Fe
2O
3), of slate are found in the matrix. Addi-
tionally, the amount of these elements increased with higherfiller
loadings, confirming progressive incorporation of WSD particles
into the matrix. Importantly, the noticeable unlisted peak atca
2.2 keV in the EDS spectrum is due to the presence of coated gold
on the composites. It can be seen in Fig.
4(b)that rPET_2.5WSD
has a relatively smooth surface as compared to higher WSD-
Figure 4.SEM images of the injection-molded surface of (a) neat rPET, (b) rPET_2.5WSD, (c) rPET_5WSD, (d) rPET_10WSD and (e) rPET_20WSD; and cor-
responding EDS spectra of (f) neat rPET, (g) rPET_2.5WSD, (h) rPET_5WSD, (i) rPET_10WSD and (j) rPET_20WSD.
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loaded rPET composites. This is due to better mixing of the WSD
particles within the polymer matrix at lower concentration
(i.e. 2.5 wt%). As thefiller content increases, the rigid WSD parti-
cles become more apparent on the surface, resulting in increased
surface roughness. A uniformfiller distribution was obtained for
up to 5 wt% of WSD, as shown in Fig.
4(c). Afterwards, the number
offiller particles increased on the surface with increasing concen-
tration of WSD (Fig.4(c)–(e)). Asfiller concentration grows,
the likelihood of their agglomeration also increases. The agglom-
eration phenomenon began on the surface when thefiller loading
reached or exceeded 10 wt%, as shown by ellipses in Fig.
4(d),(e).
This trend is in agreement with previous studies on mineral-filled
composites, where highfiller loadings lead to agglomeration and
void formation.
18,36
Notably, the observed surfaces were free of
cracks and delamination. This indicates good processability and
compatibility between rPET and WSD under the used injection-
molding conditions.
Physical properties
The evaluation of the composite's density (theoretical and exper-
imental) and void content (%) as a function of WSD content is
depicted in Fig.
5. It was observed that the densities, both theoret-
ical and experimental, increased with increasing WSD
concentration and ranged from 1.31 to 1.47 g cm
−3
. The
enhancement in density with increased WSD (densi-
ty=2.51 g cm
−3
) content may be ascribed to its higher density
than rPET (density=1.33 g cm
−3
). Moreover, the results show
that the pure rPET composite had the smallest value of void con-
tent (ca1.65%). When comparing, it was seen that the void con-
tent of the rPET_20WSD composite grew by around 36% and
stayed the highest at 2.25%. This indicates that the void content
increases as the concentration of WSD rises. At lower concentra-
tions, WSD particles disperse more uniformly, minimizing void for-
mation. In contrast, at higher loadings, agglomeration and
insufficient polymer–filler wetting likely lead to microvoids and
entrapment of air during processing. At an industrial scale, this
issue could be resolved by optimizing processing parameters.
Tensile properties
Fig.
6presents the variation of tensile properties of the WSD-filled
rPET composites. Fig.6(a)displays the stress–strain curves of rPET
and its composites. The slope of the initial linear portion increases
with WSD content, suggesting improved stiffness. In contrast, pro-
nounced yield and ultimate tensile points suggest effective load
transfer from the matrix to the slate particles. According to
Fig.
6(b),unfilled rPET has a tensile strength of 38.07 MPa. The
Figure 4(Continued)
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particles within the polymer matrix at lower concentration
(i.e. 2.5 wt%). As thefiller content increases, the rigid WSD parti-
cles become more apparent on the surface, resulting in increased
surface roughness. A uniformfiller distribution was obtained for
up to 5 wt% of WSD, as shown in Fig.
4(c). Afterwards, the number
offiller particles increased on the surface with increasing concen-
tration of WSD (Fig.4(c)–(e)). Asfiller concentration grows,
the likelihood of their agglomeration also increases. The agglom-
eration phenomenon began on the surface when thefiller loading
reached or exceeded 10 wt%, as shown by ellipses in Fig.
4(d),(e).
This trend is in agreement with previous studies on mineral-filled
composites, where highfiller loadings lead to agglomeration and
void formation.
18,36
Notably, the observed surfaces were free of
cracks and delamination. This indicates good processability and
compatibility between rPET and WSD under the used injection-
molding conditions.
Physical properties
The evaluation of the composite's density (theoretical and exper-
imental) and void content (%) as a function of WSD content is
depicted in Fig.
5. It was observed that the densities, both theoret-
ical and experimental, increased with increasing WSD
concentration and ranged from 1.31 to 1.47 g cm
−3
. The
enhancement in density with increased WSD (densi-
ty=2.51 g cm
−3
) content may be ascribed to its higher density
than rPET (density=1.33 g cm
−3
). Moreover, the results show
that the pure rPET composite had the smallest value of void con-
tent (ca1.65%). When comparing, it was seen that the void con-
tent of the rPET_20WSD composite grew by around 36% and
stayed the highest at 2.25%. This indicates that the void content
increases as the concentration of WSD rises. At lower concentra-
tions, WSD particles disperse more uniformly, minimizing void for-
mation. In contrast, at higher loadings, agglomeration and
insufficient polymer–filler wetting likely lead to microvoids and
entrapment of air during processing. At an industrial scale, this
issue could be resolved by optimizing processing parameters.
Tensile properties
Fig.
6presents the variation of tensile properties of the WSD-filled
rPET composites. Fig.6(a)displays the stress–strain curves of rPET
and its composites. The slope of the initial linear portion increases
with WSD content, suggesting improved stiffness. In contrast, pro-
nounced yield and ultimate tensile points suggest effective load
transfer from the matrix to the slate particles. According to
Fig.
6(b),unfilled rPET has a tensile strength of 38.07 MPa. The
Figure 4(Continued)
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incorporation of WSD improved tensile strength by approxi-
mately 0.5% at 2.5 wt% and 2.3% at 5 wt% compared to neat rPET.
Notably, the composite containing 5 wt% WSD showed a statisti-
cally significant improvement (P<0.05). However, positive influ-
ence was only observed up to 5 wt% offiller loading. Further
addition of WSD caused a reduction in strength values, falling
by approximately 0.8% for rPET_10WSD and 2.1% for
rPET_20WSD. At higher loadings (≥10 wt%), agglomerated WSD
particles disrupt uniform stress transfer and reduce effective inter-
facial contact. This compromises tensile strength despite increas-
ingfiller content. At the microstructural level, slate particles
impede local chain mobility, increasing stiffness while reducing
the possibility of strain hardening. When agglomerates form,
stress distribution becomes highly anisotropic, concentrating
the load at particle–matrix interfaces that act as microcrack initia-
tion sites.
Existing research reports consistent results regarding tensile
strength when polymers are reinforced with particulatefillers.
Figure 5.Density and void content of composites.
Figure 6.(a) Stress–strain curves, (b) tensile strength, (c) Young's modulus and (d) elongation at break of composites containing 0–20 wt% WSD. (Bars
with the same letter are not significantly different according to the Tukey test atP<0.05.)
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mately 0.5% at 2.5 wt% and 2.3% at 5 wt% compared to neat rPET.
Notably, the composite containing 5 wt% WSD showed a statisti-
cally significant improvement (P<0.05). However, positive influ-
ence was only observed up to 5 wt% offiller loading. Further
addition of WSD caused a reduction in strength values, falling
by approximately 0.8% for rPET_10WSD and 2.1% for
rPET_20WSD. At higher loadings (≥10 wt%), agglomerated WSD
particles disrupt uniform stress transfer and reduce effective inter-
facial contact. This compromises tensile strength despite increas-
ingfiller content. At the microstructural level, slate particles
impede local chain mobility, increasing stiffness while reducing
the possibility of strain hardening. When agglomerates form,
stress distribution becomes highly anisotropic, concentrating
the load at particle–matrix interfaces that act as microcrack initia-
tion sites.
Existing research reports consistent results regarding tensile
strength when polymers are reinforced with particulatefillers.
Figure 5.Density and void content of composites.
Figure 6.(a) Stress–strain curves, (b) tensile strength, (c) Young's modulus and (d) elongation at break of composites containing 0–20 wt% WSD. (Bars
with the same letter are not significantly different according to the Tukey test atP<0.05.)
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Lendvaiet al.
18
conducted a study to examine the effects of differ-
ent concentrations of waste marble dust, ranging from 0 to 20 wt
%, on the mechanical characteristics of rPET. They discovered that
the tensile strength peaked at afiller loading of 2.5 wt% and
decreased afterwards. Khanet al.
22
studied the effect of WSD par-
ticles (varying from 0 to 15 wt%) on poly(lactic acid). They
reported that the tensile strength of the composites increased
when the WSD content was increased, until afiller load of 5 wt
%. Nevertheless, the inclusion of morefiller beyond this threshold
resulted in a decrease in tensile strength. Similarly, Thumsorn
et al.
43
added 10 wt% CaCO
3to rPET and observed a decline of
approximately 8% in the strength value.
In contrast to the observed trend in the tested composites’ten-
sile strength, the values for Young's modulus showed an upward
trend as the WSD particle loading increased (Fig.6(c)). The unfilled
rPET showed the lowest Young's modulus of 2.14 GPa. In compar-
ison, the composites with 2.5, 5 and 10 wt% WSD exhibited an
increased Young's modulus by approximately 3%, 11% and 17%,
respectively. The composite rPET_20WSD, which contains 20 wt
% WSD particles, achieved a Young's modulus of 3 GPa, a signifi-
cant increase of more than 40% over that of unaltered rPET. The
increase in Young's modulus of composites is due to the higher
stiffness of WSD particles compared to rPET matrix. Their presence
results in the restricted mobility of the molecular chains during
the early testing phase, even when the components demonstrate
limited adhesion. This explain the continued increase in Young's
modulus beyond 5 wt% despite the decline in tensile strength.
Thesefindings align with previous research that reported an ele-
vated Young's modulus of several polymer composites. Thumsorn
et al.
43
observedca15% enhancement in tensile modulus with a
10 wt% CaCO
3incorporation in a rPET matrix. Similarly, the addi-
tion of 10 wt% talc enhanced the modulus of rPET by approxi-
mately 26%.
44
Moreover, the incorporation of elevated
quantities of marble dust (ca43%) at a loading of 20 wt% was
documented to significantly improve the Young's modulus of
rPET composites.
18
In addition, incorporating slate particles
improved Young's modulus of polyamide, poly(lactic acid) and
acrylonitrile–butadiene–styrene-based composites.
22,30,32
The elongation at break decreased steadily with increasing WSD
in rPET composites (Fig.6(d)). The highest elongation was
observed in the unaltered rPET (13.30%). The composites showed
elongation of 8.93% (rPET_2.5WSD), 8.43% (rPET_5WSD), 4.47%
(rPET_10WSD) and 2.57% (rPET_20WSD), respectively. The
observed decline in elongation at break reflects diminished duc-
tility and toughness because of stifferfiller particles disrupting
the polymer's energy dissipation mechanisms.
30,45
Fig.7depicts
the fractured surfaces of tensile broken samples of rPET
(Fig.7(a)), rPET_2.5WSD (Fig.7(b)), rPET_5WSD (Fig.7(c)),
rPET_10WSD (Fig.7(d)) and rPET_20WSD (Fig.7(e)). The images
in Fig.7show that neat rPET, rPET_2.5WSD and rPET_5WSD exhib-
ited a homogeneous morphology with few voids/pores. As seen
in Fig.
7(b),(c), the presence offiller particles inside the rPET/
WSD composites resulted in the formation of a network. This net-
work effectively strengthened the composite material under load-
ing conditions and prevented fracture development. These
observations correlate well with the results obtained from tensile
strength data. On the other hand, distinct characteristics were
seen for rPET_10WSD and rPET_20WSD. The fractured surfaces
revealed multiple pores/voids along with interfacial gaps
between rPET and WSD. SEM images (Fig.
7(d),(e)) show thatfiller
agglomerates at≥10 wt% loading reduce interfacial bonding and
act as a stress concentrator, leading to embrittlement of the rPET/
WSD composites. When particles aggregate, interfacial surface
area decreases, resulting in less reinforcing efficiency of the
filler.
46
Such aggregation is generally disadvantageous for com-
posite materials as it deteriorates their mechanical properties.
These results also support the impact strengthfindings, where
reduced interparticle distance markedly decreased composite
ductility.
Flexural properties
Fig.
8illustrates theflexural behavior of the rPET/WSD composites,
offering insight into their load-bearing capacity under bending
conditions. Fig.
8(a)shows the stress–strain curves obtained dur-
ingflexural testing, highlighting thatflexural stress increases
whileflexural strain decreases with increased WSD concentration.
Fig.8(b),(c)shows that neat rPET has aflexural strength of
72.50 MPa and aflexural modulus of 2.11 GPa, and both steadily
increased for up to 20 wt% WSD addition.
Unlike the tensile results, the higher loading of WSD particles
contributed positively toflexural strength. Theflexural strength
increased by 3.0%, 3.5%, 3.6% and 5.9% for rPET composites con-
taining 2.5, 5, 10 and 20 wt% WSD, respectively. The rise can be
attributed to the fact that the specimen is subjected to both com-
pressive and tensile forces simultaneously underflexural loading.
This combined tensile–compressive stress state allows slate parti-
cles to serve as effective load bridges across the neutral axis. As a
result, stress transfer becomes more symmetric across the struc-
ture, even at the sites where agglomerates are present. Literature
reports comparablefindings on the enhancedflexural strength of
rPET with wastefiller. Lendvaiet al.
18
observed almost a 3%
enhancement inflexural strength when 20 wt% of marble dust
was added to rPET. Likewise, Khanet al.
22
reported that adding
15 wt% WSD particles improves theflexural strength of
poly(lactic acid) byca10%.
According to Fig.8(c), there is a consistent increase inflexural
modulus with increasing WSD particles. For instance, the
flexural modulus of rPET_2.5WSD (2.25 GPa) increased byca
7% compared to unfilled rPET (2.11 GPa). Similarly, the com-
posite containing 10 wt% WSD particles (rPET_10WSD) exhib-
ited an improvement ofca22% inflexural modulus, reaching
a value of 2.57 GPa. Theflexural modulus of the composite with
20 wt% WSD particles peaked at 3.19 GPa (ca52% more than
unfilled rPET). The statistical analysis confirmed that the
improvements inflexural modulus observed at each incremen-
tal level of slate loading were significant. The higher modulus is
attributed to the incorporation of stiff reinforcingfiller units
inside the polymer matrix.
47
Thefindings align with previous
studies reporting improvedflexural modulus in polymer com-
posites supplemented with different wastefillers. Lendvai
et al.
18
found that the addition of 20 wt% waste marble dust
to rPET resulted in an increase ofca32% in theflexural modu-
lus. Also, the addition of WSD has been shown to enhance the
flexural modulus of other polymers, such as poly(lactic acid),
22
high-density polyethylene
25
and acrylonitrile–butadiene–sty-
rene.
30
In this study, allfilled composites performed better
than neat rPET inflexural strength and modulus values. The
flexural strain at break of thecomposites is presented in
Fig.8(d). Neat rPET showed a strain at break of 7.43%, which
reduced to 3.40% for rPET_20WSD, reflecting a reduction of
ca52%. The change indicates the gradual stiffening and
embrittlement of the material with elevatedfiller content, as
the rigid WSD particles impede polymer chain mobility and
reduce the matrix's capacity for plastic deformation.
47
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18
conducted a study to examine the effects of differ-
ent concentrations of waste marble dust, ranging from 0 to 20 wt
%, on the mechanical characteristics of rPET. They discovered that
the tensile strength peaked at afiller loading of 2.5 wt% and
decreased afterwards. Khanet al.
22
studied the effect of WSD par-
ticles (varying from 0 to 15 wt%) on poly(lactic acid). They
reported that the tensile strength of the composites increased
when the WSD content was increased, until afiller load of 5 wt
%. Nevertheless, the inclusion of morefiller beyond this threshold
resulted in a decrease in tensile strength. Similarly, Thumsorn
et al.
43
added 10 wt% CaCO
3to rPET and observed a decline of
approximately 8% in the strength value.
In contrast to the observed trend in the tested composites’ten-
sile strength, the values for Young's modulus showed an upward
trend as the WSD particle loading increased (Fig.6(c)). The unfilled
rPET showed the lowest Young's modulus of 2.14 GPa. In compar-
ison, the composites with 2.5, 5 and 10 wt% WSD exhibited an
increased Young's modulus by approximately 3%, 11% and 17%,
respectively. The composite rPET_20WSD, which contains 20 wt
% WSD particles, achieved a Young's modulus of 3 GPa, a signifi-
cant increase of more than 40% over that of unaltered rPET. The
increase in Young's modulus of composites is due to the higher
stiffness of WSD particles compared to rPET matrix. Their presence
results in the restricted mobility of the molecular chains during
the early testing phase, even when the components demonstrate
limited adhesion. This explain the continued increase in Young's
modulus beyond 5 wt% despite the decline in tensile strength.
Thesefindings align with previous research that reported an ele-
vated Young's modulus of several polymer composites. Thumsorn
et al.
43
observedca15% enhancement in tensile modulus with a
10 wt% CaCO
3incorporation in a rPET matrix. Similarly, the addi-
tion of 10 wt% talc enhanced the modulus of rPET by approxi-
mately 26%.
44
Moreover, the incorporation of elevated
quantities of marble dust (ca43%) at a loading of 20 wt% was
documented to significantly improve the Young's modulus of
rPET composites.
18
In addition, incorporating slate particles
improved Young's modulus of polyamide, poly(lactic acid) and
acrylonitrile–butadiene–styrene-based composites.
22,30,32
The elongation at break decreased steadily with increasing WSD
in rPET composites (Fig.6(d)). The highest elongation was
observed in the unaltered rPET (13.30%). The composites showed
elongation of 8.93% (rPET_2.5WSD), 8.43% (rPET_5WSD), 4.47%
(rPET_10WSD) and 2.57% (rPET_20WSD), respectively. The
observed decline in elongation at break reflects diminished duc-
tility and toughness because of stifferfiller particles disrupting
the polymer's energy dissipation mechanisms.
30,45
Fig.7depicts
the fractured surfaces of tensile broken samples of rPET
(Fig.7(a)), rPET_2.5WSD (Fig.7(b)), rPET_5WSD (Fig.7(c)),
rPET_10WSD (Fig.7(d)) and rPET_20WSD (Fig.7(e)). The images
in Fig.7show that neat rPET, rPET_2.5WSD and rPET_5WSD exhib-
ited a homogeneous morphology with few voids/pores. As seen
in Fig.
7(b),(c), the presence offiller particles inside the rPET/
WSD composites resulted in the formation of a network. This net-
work effectively strengthened the composite material under load-
ing conditions and prevented fracture development. These
observations correlate well with the results obtained from tensile
strength data. On the other hand, distinct characteristics were
seen for rPET_10WSD and rPET_20WSD. The fractured surfaces
revealed multiple pores/voids along with interfacial gaps
between rPET and WSD. SEM images (Fig.
7(d),(e)) show thatfiller
agglomerates at≥10 wt% loading reduce interfacial bonding and
act as a stress concentrator, leading to embrittlement of the rPET/
WSD composites. When particles aggregate, interfacial surface
area decreases, resulting in less reinforcing efficiency of the
filler.
46
Such aggregation is generally disadvantageous for com-
posite materials as it deteriorates their mechanical properties.
These results also support the impact strengthfindings, where
reduced interparticle distance markedly decreased composite
ductility.
Flexural properties
Fig.
8illustrates theflexural behavior of the rPET/WSD composites,
offering insight into their load-bearing capacity under bending
conditions. Fig.
8(a)shows the stress–strain curves obtained dur-
ingflexural testing, highlighting thatflexural stress increases
whileflexural strain decreases with increased WSD concentration.
Fig.8(b),(c)shows that neat rPET has aflexural strength of
72.50 MPa and aflexural modulus of 2.11 GPa, and both steadily
increased for up to 20 wt% WSD addition.
Unlike the tensile results, the higher loading of WSD particles
contributed positively toflexural strength. Theflexural strength
increased by 3.0%, 3.5%, 3.6% and 5.9% for rPET composites con-
taining 2.5, 5, 10 and 20 wt% WSD, respectively. The rise can be
attributed to the fact that the specimen is subjected to both com-
pressive and tensile forces simultaneously underflexural loading.
This combined tensile–compressive stress state allows slate parti-
cles to serve as effective load bridges across the neutral axis. As a
result, stress transfer becomes more symmetric across the struc-
ture, even at the sites where agglomerates are present. Literature
reports comparablefindings on the enhancedflexural strength of
rPET with wastefiller. Lendvaiet al.
18
observed almost a 3%
enhancement inflexural strength when 20 wt% of marble dust
was added to rPET. Likewise, Khanet al.
22
reported that adding
15 wt% WSD particles improves theflexural strength of
poly(lactic acid) byca10%.
According to Fig.8(c), there is a consistent increase inflexural
modulus with increasing WSD particles. For instance, the
flexural modulus of rPET_2.5WSD (2.25 GPa) increased byca
7% compared to unfilled rPET (2.11 GPa). Similarly, the com-
posite containing 10 wt% WSD particles (rPET_10WSD) exhib-
ited an improvement ofca22% inflexural modulus, reaching
a value of 2.57 GPa. Theflexural modulus of the composite with
20 wt% WSD particles peaked at 3.19 GPa (ca52% more than
unfilled rPET). The statistical analysis confirmed that the
improvements inflexural modulus observed at each incremen-
tal level of slate loading were significant. The higher modulus is
attributed to the incorporation of stiff reinforcingfiller units
inside the polymer matrix.
47
Thefindings align with previous
studies reporting improvedflexural modulus in polymer com-
posites supplemented with different wastefillers. Lendvai
et al.
18
found that the addition of 20 wt% waste marble dust
to rPET resulted in an increase ofca32% in theflexural modu-
lus. Also, the addition of WSD has been shown to enhance the
flexural modulus of other polymers, such as poly(lactic acid),
22
high-density polyethylene
25
and acrylonitrile–butadiene–sty-
rene.
30
In this study, allfilled composites performed better
than neat rPET inflexural strength and modulus values. The
flexural strain at break of thecomposites is presented in
Fig.8(d). Neat rPET showed a strain at break of 7.43%, which
reduced to 3.40% for rPET_20WSD, reflecting a reduction of
ca52%. The change indicates the gradual stiffening and
embrittlement of the material with elevatedfiller content, as
the rigid WSD particles impede polymer chain mobility and
reduce the matrix's capacity for plastic deformation.
47
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Shore D hardness
Fig.9(a)shows the shore D hardness values of the prepared rPET/
WSD composites. The rPET withoutfiller content exhibits the
lowest value of 76.1 Shore D. The incorporation of WSD led to
an increase in hardness, with rPET_2.5WSD, rPET_5WSD,
rPET_10WSD and rPET_20WSD showing improvements of 1.09%,
Figure 7.SEM images of tensile fractured surfaces: (a) neat rPET, (b) rPET_2.5WSD, (c) rPET_5WSD, (d) rPET_10WSD and (e) rPET_20WSD.
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Fig.9(a)shows the shore D hardness values of the prepared rPET/
WSD composites. The rPET withoutfiller content exhibits the
lowest value of 76.1 Shore D. The incorporation of WSD led to
an increase in hardness, with rPET_2.5WSD, rPET_5WSD,
rPET_10WSD and rPET_20WSD showing improvements of 1.09%,
Figure 7.SEM images of tensile fractured surfaces: (a) neat rPET, (b) rPET_2.5WSD, (c) rPET_5WSD, (d) rPET_10WSD and (e) rPET_20WSD.
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1.32%, 1.75% and 2.63%, respectively. This enhancement in hard-
ness can be attributed to the presence of rigid WSD particles
within the rPET matrix. Which restricts local molecular mobility
and enhances the resistance to surface deformation of rPET.
46
Allfilled composites showed higher resistance to deformation,
reflected in higher hardness values with increasedfiller content.
Thesefindings agree with previous research showing that adding
an inorganicfiller to a polymer increases its hardness values.
48
For
example, the addition of 25 wt% of CaCO
3to polypropylene
improved its hardness from 59.20 to 65.83.
49
Similarly, the incor-
poration of 20 wt% waste marble dust into rPET led to an increase
ofca3% in Shore D hardness.
18
Impact strength
The impact strength of rPET composites with variation in WSD
content is presented in Fig.9(b). The results show that the tough-
ness of composite specimens decreased as the amount of WSD
increased in the matrix. The unaltered rPET showed the highest
impact strength of 19.63 kJ m
−2
, which dropped to 14.73 kJ m
−2
when 2.5 wt% WDS was added. rPET with 5 wt%filler displayed
similar impact properties (14.80 kJ m
−2
). However, adding more
WSD decreased impact strength from this point onwards. Among
all samples, rPET containing 20 wt%filler demonstrated the low-
est impact strength of 10 kJ m
−2
(ca50% lower than that of pure
rPET). The decrease in impact resistance was possibly caused by
the inadequate attachment of WSD particles to the rPET matrix.
The presence of WSD particles creates voids and microstructural
discontinuities that function as stress concentrators, hence reduc-
ing the composite's capacity to absorb impact energy. The effects
further intensify at elevatedfiller loadings due to enhanced parti-
cle agglomeration and interfacial imperfections.
50
Also, at a sud-
den load, the relaxation time of rPET chains decreases,
preventing them from redistributing stresses around rigid inclu-
sions. As a result, the local stress rapidly exceeds the matrix yield
strength, causing cracks to propagate along weak interfaces.
These observations are consistent with previous studies. Sharma
and Mahanwar
17
reported an 83% decrease in the impact
strength of rPET compositesfilled with 40 wt%fly ash. Lendvai
et al.
18
observed a reduction from 30.94 to 13.15 kJ m
−2
in rPET
with 20 wt% waste marble dust. Even conventional commercial
Figure 8.(a) Stress–strain curves, (b)flexural strength, (c)flexural modulus and (d)flexural strain at break of composites containing 0–20 wt% WSD. (Bars
with the same letter are not significantly different according to the Tukey test atP<0.05.)
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ness can be attributed to the presence of rigid WSD particles
within the rPET matrix. Which restricts local molecular mobility
and enhances the resistance to surface deformation of rPET.
46
Allfilled composites showed higher resistance to deformation,
reflected in higher hardness values with increasedfiller content.
Thesefindings agree with previous research showing that adding
an inorganicfiller to a polymer increases its hardness values.
48
For
example, the addition of 25 wt% of CaCO
3to polypropylene
improved its hardness from 59.20 to 65.83.
49
Similarly, the incor-
poration of 20 wt% waste marble dust into rPET led to an increase
ofca3% in Shore D hardness.
18
Impact strength
The impact strength of rPET composites with variation in WSD
content is presented in Fig.9(b). The results show that the tough-
ness of composite specimens decreased as the amount of WSD
increased in the matrix. The unaltered rPET showed the highest
impact strength of 19.63 kJ m
−2
, which dropped to 14.73 kJ m
−2
when 2.5 wt% WDS was added. rPET with 5 wt%filler displayed
similar impact properties (14.80 kJ m
−2
). However, adding more
WSD decreased impact strength from this point onwards. Among
all samples, rPET containing 20 wt%filler demonstrated the low-
est impact strength of 10 kJ m
−2
(ca50% lower than that of pure
rPET). The decrease in impact resistance was possibly caused by
the inadequate attachment of WSD particles to the rPET matrix.
The presence of WSD particles creates voids and microstructural
discontinuities that function as stress concentrators, hence reduc-
ing the composite's capacity to absorb impact energy. The effects
further intensify at elevatedfiller loadings due to enhanced parti-
cle agglomeration and interfacial imperfections.
50
Also, at a sud-
den load, the relaxation time of rPET chains decreases,
preventing them from redistributing stresses around rigid inclu-
sions. As a result, the local stress rapidly exceeds the matrix yield
strength, causing cracks to propagate along weak interfaces.
These observations are consistent with previous studies. Sharma
and Mahanwar
17
reported an 83% decrease in the impact
strength of rPET compositesfilled with 40 wt%fly ash. Lendvai
et al.
18
observed a reduction from 30.94 to 13.15 kJ m
−2
in rPET
with 20 wt% waste marble dust. Even conventional commercial
Figure 8.(a) Stress–strain curves, (b)flexural strength, (c)flexural modulus and (d)flexural strain at break of composites containing 0–20 wt% WSD. (Bars
with the same letter are not significantly different according to the Tukey test atP<0.05.)
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fillers show similar behavior. For example, 25 wt% loading of
CaCO
3to polypropylene resulted in an impact strength reduction
of nearly 55%.
49
Specific wear rate
As shown in Fig.10, the specific wear rate of the rPET composites
was affected by the concentration of WSD. The pure rPET had a spe-
cific wear rate of 6.37×10
−9
cm
3
N
−1
m
−1
. An initial increase in
specific wear rate was observed with 2.5 wt% WSD loading. How-
ever, further increases infiller content led to a consistent decline.
The composite with a loading of 2.5 wt% WSD exhibited the maxi-
mum specific wear rate of 7.57×10
−9
cm
3
N
−1
m
−1
, while the
composite with 20 wt% WSD content had the lowest specificwear
rate of 2.32×10
−9
cm
3
N
−1
m
−1
.Compositesloadedwith20wt%
WSD had a specific wear rate almost 64% lower than that of pure
rPET. Neat rPET exhibits higher wear rates due to surface softening
and material removal caused by its low hardness and thermal insta-
bility under frictional heating. At 2.5 wt% loading, the number of
WSD particles embedded near the surface appears insufficient to
form a continuous protective barrier, leading to localized matrix
degradation under sliding contact. When greater concentrations
(≥5wt%)ofWSDfiller particles are introduced into the rPET matrix,
the number offiller particles on the composite surface increases
and are rubbed along with the matrix while sliding. Consequently,
increasing the WSD content in the rPET matrix enhances its resis-
tance to deformation during sliding and reduces matrix detach-
ment.
51
This leads to a decrease in weight loss, as found
experimentally. The observed reduction in wear rate at higher
WSD content is further supported by the increased Shore D hard-
ness of the composites, which enhances resistance to plastic defor-
mation during sliding. The observed reduction in wear rate also
relates to tribochemical factors. Siliceous and alumina-rich WSD
particles most likely help in the formation of a thin, cohesive trans-
ferfilm during sliding, stabilizing the contact and reducing adhe-
sive junctions.
52,53
Similar trends have been reported in the literature, linking
improved wear resistance of polymer composites to higher load-
ings of wastefillers. Thus, Lendvaiet al.
18
found that the addition
of 20 wt% waste marble dust to rPET resulted in a wear reduction
of about 44% compared to unfilled rPET. Awadet al.
54
found that
adding 50% waste marble dust reduced the weight loss of low-
density polyethylene by up to 93%. Other mineralfillers, such as
CaCO
3and talc, have shown comparable improvements in terms
of wear reduction by limiting plastic deformation and altering sur-
face damage mechanisms.
55,56
CONCLUSIONS
This study shows the potential of WSD as a reinforcingfiller in
rPET. Composites with 0–20 wt% WSD were fabricated and evalu-
ated for their physical, mechanical, morphological and tribologi-
cal properties. The main conclusions drawn from the results are
listed as follows:
Composite density increased from 1.31 g cm
−3
(neat rPET) to
1.47 g cm
−3
(20 wt% WSD), while void content rose modestly
from 1.65% to 2.25%.
Young's modulus improved steadily (2.14 to 3.00 GPa), andflex-
ural modulus rose from 2.11 to 3.19 GPa, confirming the stiffen-
ing effect of WSD.
Figure 9.(a) Shore D hardness and (b) Izod impact strength of unaltered rPET and rPET/WSD composites. (Bars with the same letter are not significantly
different according to the Tukey test atP<0.05.)
Figure 10.Specific wear rate of unaltered rPET and rPET/WSD
composites.
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CaCO
3to polypropylene resulted in an impact strength reduction
of nearly 55%.
49
Specific wear rate
As shown in Fig.10, the specific wear rate of the rPET composites
was affected by the concentration of WSD. The pure rPET had a spe-
cific wear rate of 6.37×10
−9
cm
3
N
−1
m
−1
. An initial increase in
specific wear rate was observed with 2.5 wt% WSD loading. How-
ever, further increases infiller content led to a consistent decline.
The composite with a loading of 2.5 wt% WSD exhibited the maxi-
mum specific wear rate of 7.57×10
−9
cm
3
N
−1
m
−1
, while the
composite with 20 wt% WSD content had the lowest specificwear
rate of 2.32×10
−9
cm
3
N
−1
m
−1
.Compositesloadedwith20wt%
WSD had a specific wear rate almost 64% lower than that of pure
rPET. Neat rPET exhibits higher wear rates due to surface softening
and material removal caused by its low hardness and thermal insta-
bility under frictional heating. At 2.5 wt% loading, the number of
WSD particles embedded near the surface appears insufficient to
form a continuous protective barrier, leading to localized matrix
degradation under sliding contact. When greater concentrations
(≥5wt%)ofWSDfiller particles are introduced into the rPET matrix,
the number offiller particles on the composite surface increases
and are rubbed along with the matrix while sliding. Consequently,
increasing the WSD content in the rPET matrix enhances its resis-
tance to deformation during sliding and reduces matrix detach-
ment.
51
This leads to a decrease in weight loss, as found
experimentally. The observed reduction in wear rate at higher
WSD content is further supported by the increased Shore D hard-
ness of the composites, which enhances resistance to plastic defor-
mation during sliding. The observed reduction in wear rate also
relates to tribochemical factors. Siliceous and alumina-rich WSD
particles most likely help in the formation of a thin, cohesive trans-
ferfilm during sliding, stabilizing the contact and reducing adhe-
sive junctions.
52,53
Similar trends have been reported in the literature, linking
improved wear resistance of polymer composites to higher load-
ings of wastefillers. Thus, Lendvaiet al.
18
found that the addition
of 20 wt% waste marble dust to rPET resulted in a wear reduction
of about 44% compared to unfilled rPET. Awadet al.
54
found that
adding 50% waste marble dust reduced the weight loss of low-
density polyethylene by up to 93%. Other mineralfillers, such as
CaCO
3and talc, have shown comparable improvements in terms
of wear reduction by limiting plastic deformation and altering sur-
face damage mechanisms.
55,56
CONCLUSIONS
This study shows the potential of WSD as a reinforcingfiller in
rPET. Composites with 0–20 wt% WSD were fabricated and evalu-
ated for their physical, mechanical, morphological and tribologi-
cal properties. The main conclusions drawn from the results are
listed as follows:
Composite density increased from 1.31 g cm
−3
(neat rPET) to
1.47 g cm
−3
(20 wt% WSD), while void content rose modestly
from 1.65% to 2.25%.
Young's modulus improved steadily (2.14 to 3.00 GPa), andflex-
ural modulus rose from 2.11 to 3.19 GPa, confirming the stiffen-
ing effect of WSD.
Figure 9.(a) Shore D hardness and (b) Izod impact strength of unaltered rPET and rPET/WSD composites. (Bars with the same letter are not significantly
different according to the Tukey test atP<0.05.)
Figure 10.Specific wear rate of unaltered rPET and rPET/WSD
composites.
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Flexural strength increased slightly from 72.5 to 76.8 MPa,
whereas tensile strength remained unchanged, showing only
an approximate 2% decline.
Elongation at break and impact strength decreased for allfilled
composites. These limitations may be overcome by improving
filler–matrix interactions, for example, via surface functionaliza-
tion, compatibilizers or hybrid reinforcement.
Shore D hardness rose slightly, whereas wear resistance
improved strongly, with the specific wear rate reduced from
6.37×10
−9
cm
3
N
−1
m
−1
for neat rPET to 2.32 ×
10
−9
cm
3
N
−1
m
−1
for composite containing 20 wt% WSD.
SEM observations revealed uniform dispersion at lowfiller levels
(≤5 wt%) and agglomeration at higher loadings, consistent with
the observed loss in elongation at break and impact strength.
Future research should include friction coefficient assessments
and analyses of worn surfaces to provide a more thorough mech-
anistic validation of the wear behavior demonstrated in this work.
The improved stiffness and wear resistance make the composites
suitable for automotive, electrical and appliance components.
Their low cost and recyclability further make the composites sus-
tainable alternatives to the virgin polymer.
AUTHOR CONTRIBUTIONS
Aditya Chauhan:Conceptualization, Methodology, Investigation,
Software, Data curation, Validation, Writing–original draft,
Writing–review & editing.Robert Brüll:Investigation, Formal
analysis, Supervision, Writing–review & editing.Subrajeet
Deshmukh:Formal analysis, Writing–review & editing.Sampat
Singh Bhati:Formal analysis, Writing–review & editing.Kirtiraj
K. Gaikwad:Methodology, Investigation, Formal analysis, Valida-
tion, Supervision, Writing–review & editing.Tej Singh:Method-
ology, Writing–original draft, Writing–review & editing.
ACKNOWLEDGEMENTS
AC would like to thank Indian Institute of Technology Roorkee (IIT
Roorkee) and the German Academic Exchange Service (DAAD) for
providing academic support and research scholarship during his
master's thesis.
REFERENCES
1 Vollmer I, Jenks MJF, Roelands MCP, White RJ, van Harmelen T, de
Wild Pet al.,Angew Chem Int Ed59:15402–15423 (2020).
2 Bennett EM and Alexandridis P,Recycling6:69 (2021).
3 Shen L and Worrell E,Handbook of Recycling. Elsevier, pp. 497–510
(2024).
https://doi.org/10.1016/B978-0-323-85514-3.00014-2.
4 Wang K, Guo C, Li J, Wang K, Cao X, Liang Set al.,J Environ Chem Eng12:
113539 (2024).
5 Bhanderi KK, Joshi JR and Patel JV,J Indian Chem Soc100:100843 (2023).
6 Singh AK, Bedi R and Kaith BS,Compos Part B Eng219:108928 (2021).
7 Khan ZI, Habib U, Mohamad ZB and Raji AM,Express Polym Lett15:
1206–1215 (2021).
8 Raheem AB, Noor ZZ, Hassan A, Abd Hamid MK, Samsudin SA and
Sabeen AH,J Clean Prod225:1052–1064 (2019).
9 Sarda P, Hanan JC, Lawrence JG and Allahkarami M,JPolymSci60:7–31
(2022).
10 Sinha V, Patel MR and Patel JV,J Polym Environ18:8–25 (2010).
11 Lendvai L, Singh T and Ronkay F,Heliyon10:e25015 (2024).
12 Maurya A, Bhattacharya A and Khare SK,Front Bioeng Biotechnol8:
602325 (2020).
13 Jones H, Saffar F, Koutsos V and Ray D,Energies14:7306 (2021).
14 Ragaert K, Delva L and Van Geem K,Waste Manag69:24–58 (2017).
15 Schyns ZOG, Patel AD and Shaver MP,Resour Conserv Recycl198:
107170 (2023).
16 Das P and Tiwari P,Thermochim Acta679:178340 (2019).
17 Sharma AK and Mahanwar PA,Int J Plast Technol14:53–64 (2010).
18 Lendvai L, Ronkay F, Wang G, Zhang S, Guo S, Ahlawat Vet al.,Polym
Compos43:3951–3959 (2022).
19 Othman N, Mohamad Z, Khan ZI and Abdullah LC,Mater Today Proc
110:87–90 (2024).
20 Habib U, Khan ZI and Mohamad ZB,Iran Polym J33:1313–1326 (2024).
21 Oti JE, Kinuthia JM, Snelson DG and Bai J,Proc Inst Civil Eng163:9
–15 (2010).
22 Khan I, Kumar N, Yadav JS, Choudhary M, Chauhan A and Singh T,
J Mater Res Technol24:703–714 (2023).
23 Samper MD, Petrucci R, Sánchez-Nacher L, Balart R and Kenny JM,Com-
pos Part B Eng71:203–209 (2015).
24 Campos M, Velasco F, Martı́nez MA and Torralba JM,J Eur Ceram Soc
24:811–819 (2004).
25 Carbonell-Verdú A, García-García D, Jordá A, Samper MD and Balart R,
Compos Part B Eng69:460–466 (2015).
26 Wichert J, Properties of slate, inSlate as Dimension Stone, pp. 61–134
(2020).
https://doi.org/10.1007/978-3-030-35667-5_4
27 Barluenga G and Hernández-Olivares F,Constr Build Mater24:1601–
1607 (2010).
28 de Carvalho GMX, Mansur HS, Vasconcelos WL and Oréfice RL,Polí-
meros17:98–103 (2007).
29 Singh T, Pattnaik P, Shekhawat D, Ranakoti L and Lendvai L,Arab J
Chem16:104695 (2023).
30 Khan I, Kumar N, Choudhary M, Kumar S and Singh T,Arab J Chem17:
105559 (2024).
31 Girge A, Goel V, Gupta G, Fuloria D, Pati PR, Sharma Aet al.,Mater Today
Proc47:2852–2863 (2021).
32 Quiles-Carrillo L, Boronat T, Montanes N, Balart R and Torres-Giner S,
Polym Test77:105875 (2019).
33 Afgan S, Ullah N, Sulaiman M, Ali I, Iqbal T, Younas Met al.,J Mater Res
Technol21:3579–3593 (2022).
34 Gao W, Ma X, Liu Y, Wang Z and Zhu Y,Powder Technol244:45–51
(2013).
35 Khan ZI, Habib U, Mohamad ZB, Tufail A, Raji AM and Khan AU,
J Thermoplast Compos Mater38:1063–1088 (2025).
36 Khan ZI, Habib U, Mohamad ZB and Khan I,Results Eng21:101731 (2024).
37 Khan ZI, Mohsin MEA, Habib U, Mousa S, Hossain SKS, Ali SSet al.,Poly-
mers (Basel)17:1433 (2025).
38 Nassar MMA, Alzebdeh KI, Pervez T, al-Hinai N, Munam A, al-Jahwari F
et al.,Iran Polym J30:269–283 (2021).
39 Torres N, Robin JJ and Boutevin B,Eur Polym J36:2075–2080 (2000).
40 Agrawal A, Purohit A, Gupta G, Nayak SK, Ranjan Pati P and
Satapathy A, Utilization of industrial waste asfiller material in the
development of polymer composites, inComposites. CRC Press,
Boca Raton, FL, pp. 66–85 (2024).
41 Mishra SK, Purohit A, Palanimuthu S and Kumar A,Plast Rubber Compos
Macromol Eng54:69–
81 (2025).
42 Pradhan P, Purohit A, Singh J, Subudhi C, Mohapatra SS, Rout Det al.,
J Inst Eng (India) Ser E103:339–345 (2022).
43 Thumsorn S, Yamada K, Leong YW and Hamada H,Mater Sci Appl02:
59–69 (2011).
44 Droß M, Ehleben M and Dröder K,Polymers (Basel)17:259 (2025).
45 Çınar ME and Kar F,Constr Build Mater163:734–741 (2018).
46 Lendvai L, Singh T, Fekete G, Patnaik A and Dogossy G,J Polym Environ
29:2952–2963 (2021).
47 Fu S-Y, Feng X-Q, Lauke B and Mai Y-W,Compos Part B Eng39:933–961
(2008).
48 DenİzŞ, AydoğmuşE, Kar F and Arslanoğlu H,Polymer-Plastics Tech Mat
63:1498–1513 (2024).
49 Budiyantoro C, Sosiati H, Kamiel BP and Fikri MLS,IOP Conf Ser Mater Sci
Eng432:012043 (2018).
50 Habib U, Mohsin MEA, Khan ZI, Mohamad Z, Othman N, Mousa Set al.,
Polymers (Basel)17:1038 (2025).
51 Purohit A and Satapathy A,Mater Today Proc5:11906–11913 (2018).
52 Purohit A and Satapathy A,Polym Polym Compos29:S1235–S1247
(2021).
53 Gupta G, Purohit A, Kumar SS, Mohanty CP, Ray S and Pati PR,Mater
Werkst56:155–161 (2025).
54 Awad AH, Abdel-Ghany AW, Abd El-Wahab AA, El-Gamasy R and
Abdellatif MH,J Therm Anal Calorim140:2615–2623 (2020).
55 Palanikumar K, AshokGandhi R, Raghunath BK and Jayaseelan V,Mater
Today Proc16:1363–
1371 (2019).
56 Teldjoun M, Mendas M, Mzali S and Bachir Bouiadjra B,Tribol Int200:
110074 (2024).
www.soci.org A Chauhan et al.
wileyonlinelibrary.com/journal/pi © 2025 Society of Chemical Industry. Polym Int2025
12 10970126, 0, Downloaded from https://scijournals.onlinelibrary.wiley.com/doi/10.1002/pi.70043 by POLITECNICO DI MILANO, Wiley Online Library on [16/10/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
whereas tensile strength remained unchanged, showing only
an approximate 2% decline.
Elongation at break and impact strength decreased for allfilled
composites. These limitations may be overcome by improving
filler–matrix interactions, for example, via surface functionaliza-
tion, compatibilizers or hybrid reinforcement.
Shore D hardness rose slightly, whereas wear resistance
improved strongly, with the specific wear rate reduced from
6.37×10
−9
cm
3
N
−1
m
−1
for neat rPET to 2.32 ×
10
−9
cm
3
N
−1
m
−1
for composite containing 20 wt% WSD.
SEM observations revealed uniform dispersion at lowfiller levels
(≤5 wt%) and agglomeration at higher loadings, consistent with
the observed loss in elongation at break and impact strength.
Future research should include friction coefficient assessments
and analyses of worn surfaces to provide a more thorough mech-
anistic validation of the wear behavior demonstrated in this work.
The improved stiffness and wear resistance make the composites
suitable for automotive, electrical and appliance components.
Their low cost and recyclability further make the composites sus-
tainable alternatives to the virgin polymer.
AUTHOR CONTRIBUTIONS
Aditya Chauhan:Conceptualization, Methodology, Investigation,
Software, Data curation, Validation, Writing–original draft,
Writing–review & editing.Robert Brüll:Investigation, Formal
analysis, Supervision, Writing–review & editing.Subrajeet
Deshmukh:Formal analysis, Writing–review & editing.Sampat
Singh Bhati:Formal analysis, Writing–review & editing.Kirtiraj
K. Gaikwad:Methodology, Investigation, Formal analysis, Valida-
tion, Supervision, Writing–review & editing.Tej Singh:Method-
ology, Writing–original draft, Writing–review & editing.
ACKNOWLEDGEMENTS
AC would like to thank Indian Institute of Technology Roorkee (IIT
Roorkee) and the German Academic Exchange Service (DAAD) for
providing academic support and research scholarship during his
master's thesis.
REFERENCES
1 Vollmer I, Jenks MJF, Roelands MCP, White RJ, van Harmelen T, de
Wild Pet al.,Angew Chem Int Ed59:15402–15423 (2020).
2 Bennett EM and Alexandridis P,Recycling6:69 (2021).
3 Shen L and Worrell E,Handbook of Recycling. Elsevier, pp. 497–510
(2024).
https://doi.org/10.1016/B978-0-323-85514-3.00014-2.
4 Wang K, Guo C, Li J, Wang K, Cao X, Liang Set al.,J Environ Chem Eng12:
113539 (2024).
5 Bhanderi KK, Joshi JR and Patel JV,J Indian Chem Soc100:100843 (2023).
6 Singh AK, Bedi R and Kaith BS,Compos Part B Eng219:108928 (2021).
7 Khan ZI, Habib U, Mohamad ZB and Raji AM,Express Polym Lett15:
1206–1215 (2021).
8 Raheem AB, Noor ZZ, Hassan A, Abd Hamid MK, Samsudin SA and
Sabeen AH,J Clean Prod225:1052–1064 (2019).
9 Sarda P, Hanan JC, Lawrence JG and Allahkarami M,JPolymSci60:7–31
(2022).
10 Sinha V, Patel MR and Patel JV,J Polym Environ18:8–25 (2010).
11 Lendvai L, Singh T and Ronkay F,Heliyon10:e25015 (2024).
12 Maurya A, Bhattacharya A and Khare SK,Front Bioeng Biotechnol8:
602325 (2020).
13 Jones H, Saffar F, Koutsos V and Ray D,Energies14:7306 (2021).
14 Ragaert K, Delva L and Van Geem K,Waste Manag69:24–58 (2017).
15 Schyns ZOG, Patel AD and Shaver MP,Resour Conserv Recycl198:
107170 (2023).
16 Das P and Tiwari P,Thermochim Acta679:178340 (2019).
17 Sharma AK and Mahanwar PA,Int J Plast Technol14:53–64 (2010).
18 Lendvai L, Ronkay F, Wang G, Zhang S, Guo S, Ahlawat Vet al.,Polym
Compos43:3951–3959 (2022).
19 Othman N, Mohamad Z, Khan ZI and Abdullah LC,Mater Today Proc
110:87–90 (2024).
20 Habib U, Khan ZI and Mohamad ZB,Iran Polym J33:1313–1326 (2024).
21 Oti JE, Kinuthia JM, Snelson DG and Bai J,Proc Inst Civil Eng163:9
–15 (2010).
22 Khan I, Kumar N, Yadav JS, Choudhary M, Chauhan A and Singh T,
J Mater Res Technol24:703–714 (2023).
23 Samper MD, Petrucci R, Sánchez-Nacher L, Balart R and Kenny JM,Com-
pos Part B Eng71:203–209 (2015).
24 Campos M, Velasco F, Martı́nez MA and Torralba JM,J Eur Ceram Soc
24:811–819 (2004).
25 Carbonell-Verdú A, García-García D, Jordá A, Samper MD and Balart R,
Compos Part B Eng69:460–466 (2015).
26 Wichert J, Properties of slate, inSlate as Dimension Stone, pp. 61–134
(2020).
https://doi.org/10.1007/978-3-030-35667-5_4
27 Barluenga G and Hernández-Olivares F,Constr Build Mater24:1601–
1607 (2010).
28 de Carvalho GMX, Mansur HS, Vasconcelos WL and Oréfice RL,Polí-
meros17:98–103 (2007).
29 Singh T, Pattnaik P, Shekhawat D, Ranakoti L and Lendvai L,Arab J
Chem16:104695 (2023).
30 Khan I, Kumar N, Choudhary M, Kumar S and Singh T,Arab J Chem17:
105559 (2024).
31 Girge A, Goel V, Gupta G, Fuloria D, Pati PR, Sharma Aet al.,Mater Today
Proc47:2852–2863 (2021).
32 Quiles-Carrillo L, Boronat T, Montanes N, Balart R and Torres-Giner S,
Polym Test77:105875 (2019).
33 Afgan S, Ullah N, Sulaiman M, Ali I, Iqbal T, Younas Met al.,J Mater Res
Technol21:3579–3593 (2022).
34 Gao W, Ma X, Liu Y, Wang Z and Zhu Y,Powder Technol244:45–51
(2013).
35 Khan ZI, Habib U, Mohamad ZB, Tufail A, Raji AM and Khan AU,
J Thermoplast Compos Mater38:1063–1088 (2025).
36 Khan ZI, Habib U, Mohamad ZB and Khan I,Results Eng21:101731 (2024).
37 Khan ZI, Mohsin MEA, Habib U, Mousa S, Hossain SKS, Ali SSet al.,Poly-
mers (Basel)17:1433 (2025).
38 Nassar MMA, Alzebdeh KI, Pervez T, al-Hinai N, Munam A, al-Jahwari F
et al.,Iran Polym J30:269–283 (2021).
39 Torres N, Robin JJ and Boutevin B,Eur Polym J36:2075–2080 (2000).
40 Agrawal A, Purohit A, Gupta G, Nayak SK, Ranjan Pati P and
Satapathy A, Utilization of industrial waste asfiller material in the
development of polymer composites, inComposites. CRC Press,
Boca Raton, FL, pp. 66–85 (2024).
41 Mishra SK, Purohit A, Palanimuthu S and Kumar A,Plast Rubber Compos
Macromol Eng54:69–
81 (2025).
42 Pradhan P, Purohit A, Singh J, Subudhi C, Mohapatra SS, Rout Det al.,
J Inst Eng (India) Ser E103:339–345 (2022).
43 Thumsorn S, Yamada K, Leong YW and Hamada H,Mater Sci Appl02:
59–69 (2011).
44 Droß M, Ehleben M and Dröder K,Polymers (Basel)17:259 (2025).
45 Çınar ME and Kar F,Constr Build Mater163:734–741 (2018).
46 Lendvai L, Singh T, Fekete G, Patnaik A and Dogossy G,J Polym Environ
29:2952–2963 (2021).
47 Fu S-Y, Feng X-Q, Lauke B and Mai Y-W,Compos Part B Eng39:933–961
(2008).
48 DenİzŞ, AydoğmuşE, Kar F and Arslanoğlu H,Polymer-Plastics Tech Mat
63:1498–1513 (2024).
49 Budiyantoro C, Sosiati H, Kamiel BP and Fikri MLS,IOP Conf Ser Mater Sci
Eng432:012043 (2018).
50 Habib U, Mohsin MEA, Khan ZI, Mohamad Z, Othman N, Mousa Set al.,
Polymers (Basel)17:1038 (2025).
51 Purohit A and Satapathy A,Mater Today Proc5:11906–11913 (2018).
52 Purohit A and Satapathy A,Polym Polym Compos29:S1235–S1247
(2021).
53 Gupta G, Purohit A, Kumar SS, Mohanty CP, Ray S and Pati PR,Mater
Werkst56:155–161 (2025).
54 Awad AH, Abdel-Ghany AW, Abd El-Wahab AA, El-Gamasy R and
Abdellatif MH,J Therm Anal Calorim140:2615–2623 (2020).
55 Palanikumar K, AshokGandhi R, Raghunath BK and Jayaseelan V,Mater
Today Proc16:1363–
1371 (2019).
56 Teldjoun M, Mendas M, Mzali S and Bachir Bouiadjra B,Tribol Int200:
110074 (2024).
www.soci.org A Chauhan et al.
wileyonlinelibrary.com/journal/pi © 2025 Society of Chemical Industry. Polym Int2025
12 10970126, 0, Downloaded from https://scijournals.onlinelibrary.wiley.com/doi/10.1002/pi.70043 by POLITECNICO DI MILANO, Wiley Online Library on [16/10/2025]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License
Tags
slate dust
wear
tensile properties
fracture mechanism
hardness
impact properties
flexural properties
surface properties
density
void content
sem images
tensile modulus
tensile strength
flexural modulus
flexural strength
tensile strain at break
flexural strain at break
sustainable composites
recycled pet
slate pwder waste
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