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Effect of thermal conductive fillers on the properties of polypropylene composites

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We investigated the effects of various fillers such as carbon nanotube (CNT), synthetic diamond (SND), boron nitride (BN), and copper (Cu) on the properties of polypropylene (PP) composites. The thermal conductivity and stability of PP were enhanced upon the addition of thermally conductive fillers. Young’s modulus increased with filler loading, while tensile strength increased at up to 2 vol.% then decreased with elongation in all filler types. The morphology of the composite samples showed agglomeration and void content in PP/Cu composites, leading to the deterioration of thermal and mechanical properties at high-volume loading. Findings indicate that PP/CNT has better thermal and mechanical properties compared with the other types of fillers.
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Article
Effect of thermal
conductive fillers on
the properties of
polypropylene
composites
MS Nurul and M Mariatti
Abstract
We investigated the effects of various fillers such as carbon nanotube (CNT), syn-
thetic diamond (SND), boron nitride (BN), and copper (Cu) on the properties of
polypropylene (PP) composites. The thermal conductivity and stability of PP were
enhanced upon the addition of thermally conductive fillers. Young’s modulus increased
with filler loading, while tensile strength increased at up to 2 vol.% then decreased
with elongation in all filler types. The morphology of the composite samples showed
agglomeration and void content in PP/Cu composites, leading to the deterioration of
thermal and mechanical properties at high-volume loading. Findings indicate that PP/
CNT has better thermal and mechanical properties compared with the other types
of fillers.
Keywords
Thermal properties, tensile properties, conductive fillers, polypropylene, composites
Introduction
Conductive polymer composites (CPCs) are among the versatile materials that can be
used in several applications such as self-regulated heating, electromagnetic shielding,
vapor sensing, and bipolar plates in the fuel cell.
1
Reinforcement of polymers with con-
ductive fillers such as carbon nanotube (CNT), silica, synthetic diamond (SND), silicon
School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, Nibong
Tebal, Penang, Malaysia
Corresponding author:
M Mariatti, School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering
Campus, 14300 Nibong Tebal, Penang, Malaysia.
Email: mariatti@eng.usm.my
Journal of Thermoplastic Composite
Materials
26(5) 627–639
ªThe Author(s) 2011
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DOI: 10.1177/0892705711427345
jtc.sagepub.com
nitride, boron nitride (BN), copper (Cu), ferrite, bronze, and aluminum nitride can be
adapted to satisfy the required characteristics of CPCs.
2–5
Thus, CPCs are emerging
as one of the most economical and effective ways to cope with thermal management
issues.
6
In general, the effectiveness of reinforcing fillers in composites is inversely propor-
tional to the size of the filler. Previous studies reported that the absorption energy of a
smaller particle is higher than that of a larger particle due to its high surface energy.
7
Jung et al.
8
and Boudenne et al.
9
proved that the nano-sized conductive fillers in com-
posites give better thermal conductive and stability characteristics, since smaller parti-
cles have better interaction and can more easily form the conductive path than the
micron-sized particles.
Moreover, the geometry of the particle is an important factor in achieving the optimal
properties of composites. A greater surface-to-volume ratio of filler results in greater
effectiveness. Volume fraction is another factor that affects the effectiveness of the rein-
forcing filler; it should be as high as 20 by vol.%to afford satisfactory conductivity prop-
erties. However, filler loading at higher content is generally required to yield these
positive effects of fillers. This would detrimentally affect some important properties
of the polymers matrix, including processability, appearance, density, and ageing
performance.
10
In this study, we investigated the effects of four types of conductive fillers, specifi-
cally CNT, SND, BN, and Cu, in polypropylene (PP) composites. The correlations
between filler loading ranging from 0 to 4 vol.%and thermal and mechanical properties
of these composites were investigated.
Experimental
Materials
Homopolymer PP (Titanpro 6431) is a commercial product from Titan Polymer (M) Sdn.
Bhd, with a melt index of 7 g/10 min and a density of 0.9 g/cm
3
. CNT, SND, BN, and Cu
were supplied by Shenzhen Nanotech Port Co., Ltd, Heyuan Zhong Lian Nano-
technology, TaijiRing Nano-products, and Sigma Aldrich, respectively. The properties
of these fillers are presented in Table 1.
Table 1. Typical properties of thermal conductive fillers used in the study.
Properties (units) SND CNT BN CU
Thermal conductivity (W/mK) 2000 2000 300 385
Particle size distribution (nm) 5–6 2–645 30–43 379–492
Mean particle size (d
50
) 5.5 69 36 434
Density (g/cm
3
) 3.3 1.3 2.2 8.9
Shape Sphere Tube Sphere Sphere
BN: boron nitride, CNT: carbon nanotube, CU: copper, SND: synthetic diamond.
628 Journal of Thermoplastic Composite Materials 26(5)
Sample preparation
Conductive nanofillers were dried in oven at 100C for 3 h to remove moisture before
mixing with PP ranging at 1, 2, 3 and 4 vol.%of filler loading. Compounding between PP
and fillers was performed in a two-roll mill heater at a constant temperature of 185C and
at 50 rpm for 20 min. Then, the composite sheet was compression molded in an electri-
cally heated hydraulic press at 185C and subsequently cooled at 1000 psi for 3 min.
Filler characterizations
Particle size of the fillers was measured by Nanophox particle size analysis, model
NX0064. Data on particle size distribution were presented as cumulative distribution as a
function of particle size. Thermal stability of the filler was determined by thermogravi-
metric analysis (TGA)/differential thermal analysis (DTA) using Linseis model L75/04.
Fillers were heated from room temperature to 800C at a heating rate of 10C/min.
Composites characterizations
Flow behaviors of samples were determined using Dynisco Polymer Test model 4004
following the method described in American Society for Testing and Materials (ASTM)
D 1238-90b with a load of 2.16 kg at 230C and a melt time of 360 s. Cutting samples
within an interval of 10 s were weighed and melt index values were calculated in g/10 s.
Physical ashing test was performed according to ASTM D2584 to determine filler weight
fraction (W
f
) in the composites after compounding. Void content was determined from a
relationship between the theoretical density and the experimental density of the compo-
sites. Thermal conductivity was tested using a hot disc thermal constant analyzer model
TPS 2500 according to ASTM D792-98. The heat source was placed between two
448 mm samples and connected to thermal conductivity detector. TGA was per-
formed using model Perkin Elmer Pyris TGA-6. The sample was heated from room tem-
perature to 600Cat10
C/min in a nitrogen environment. Melting and crystallization
behavior of the composites was studied, employing differential scanning calorimeter
(DSC) using a Perkin-Elmer DSC-6 at a heating rate of 10C/min. Melting temperature
T
m
and crystallization temperature T
c
were derived from endothermic and exothermic
peak temperatures. The degree of crystallinity X
c
was calculated from heat of fusion
by taking 207 J/g as the enthalpy to crystallize 100%PP.
11
Tensile test was conducted
by Instron 3366 with gauge length of 50 mm and speed of 50 mm/min according to
ASTM D 638-98. The morphology of tensile fracture specimens was captured by ZEISS
SUPRA 35 VP field emission scanning electron microscope (FESEM).
Results and discussion
Melt flow index
Figure 1 illustrates the decreasing trends of melt flow index (MFI) as the conductive
filler loading was increased. These trends were expected because the incorporation of
Nurul and Mariatti 629
fillers hinders polymer flow and increases the viscosity of composites. PP/CNT exhib-
ited the lowest MFI due to the high aspect ratio of CNT, leading to strong intermolecular
interaction between the nanotubes. In contrast, the greater size of Cu (micron-sized)
resulted in a higher MFI value, which slightly increased at high Cu loading (i.e. 3 and
4 vol.%). This trend can be attributed to the metallic properties of Cu, such that it is able
to induce and catalyze the degradation of polymer composites. In addition, the heat
energy absorbed by Cu will spread to the surrounding PP matrix. Thus, the polymer
chains will be cut down, allowing MFI to increase.
12
Tensile properties
The correlation between average tensile strength and void content of PP and PP com-
posites is presented in Figure 2. SND and BN systems exhibited higher tensile strength
compared with CNT and Cu systems. The maximum tensile strength was observed at
2 vol.%, after which a decreasing trend was observed. Tensile strength was reduced at
higher nanofiller loading due to strong interactions between particle–particle rather than
particle–matrix. This trend is supported by the increasing void content as filler content
was increased. In the CNT- and Cu-filled PP systems, a decreasing trend in tensile
strength compared with that of PP was observed. This may be related to the large particle
size of Cu, which functions as a defect, and the high void content in the two-composite
systems. Increasing void content could cause detrimental effects on mechanical proper-
ties that create stress concentration and inhibit stress transfer from the matrix to the fil-
ler.
13–16
The distribution of fillers in the PP matrix at 4 vol.%was revealed by sectional
fractography of tensile test by SEM (Figure 3). PP surface (Figure 3a) was dramatically
Filler loading (vol.%)
01234
Melt flow index (g/10 s)
0
5
10
15
20
25
PP/CNT
PP/SND
PP/BN
PP/CU
Figure 1. Melt flow index (MFI) curves of polypropylene (PP) and PP composites as a function of
filler loading.
630 Journal of Thermoplastic Composite Materials 26(5)
changed by the presence of thermal conductive particles. SND and BN in Figure 3(b) and
(c) were well dispersed; the filler appears to be embedded in the PP matrix, suggesting
that the tensile strength of these systems is high. The worst dispersion and distribution
were observed in PP/Cu composites, as indicated by the presence of agglomerations and
voids in Figure 3(d). CNT was poorly distributed but was well dispersed in PP matrix
(Figure 3e). These properties of PP/Cu and PP/CNT are responsible for the increased
stress behavior and the ineffective transfer of load applied in PP composites, leading
to decreased tensile strength of CNT and Cu systems.
X
c
also influences the mechanical properties of composites.
17,18
Theoretically, the
mechanical strength of a crystalline polymer is determined by its crystalline structure.
Table 2 presents the X
c
,T
m
, and T
c
values for PP and PP composites in this study. At
4 vol.%filler loading, X
c
of SND and BN was higher than that of PP because the
crystalline region acts as a physical crosslink that enhances the tensile strength of PP
composites. In contrast, CNT and Cu systems exhibited low X
c
values since the
superficial area interferes with crystal growth, thus leading to reduced tensile strength
of the composites.
19,20
T
m
values were not significantly changed by the addition of
conductive fillers and an increase in filler loading. This may be attributed to the
maintenance of the flexibility of the polymer chain even when fillers are dispersed in
the polymer matrix.
8
T
c
values of composites were higher than that of PP and were
within the range of 110–135C, indicating that the conductive fillers can act as
nucleating agents.
Figure 4 illustrates the correlation of Young’s modulus and filler content (W
f
)ofthe
PP and PP composites. In general, the trends markedly increased with respect to the W
f
.
The highest Young’s modulus were found in CNT followed by BN, SND, and Cu fillers,
Tensile strength (MPa)
26
28
30
32
34
36
38
40
PP
PP/CNT
PP/SND
PP/BN
PP/CU
Void content (%)
0
5
10
15
20
25
30
35
Filler loading (vol.%)
01234
Figure 2. Tensile strength and void content of polypropylene (PP) and PP composites as a function
of filler loading. Bar graph refers to the tensile strength and line plot refers to the void content,
respectively.
Nurul and Mariatti 631
with increases of up to 31%,27%,25%, and 9%from that of PP, respectively. Incor-
poration of rigid and stiff reinforcement into the polymer enhanced the stiffness of the
polymer composites. Higher rigid filler content increased the Young’s modulus signif-
icantly. The PP/CNT system exhibited the highest maximum Young’s modulus due to
the high aspect ratio of CN, which leads to greater stiffening compared with particulate
composites. The lower interfacial area of the sphere shape of SND, BN, and Cu results in
lower Young’s modulus compared with CNT system. The Cu system had the lowest
Young’s modulus because of the large particle size of Cu, which results in less inter-
action between filler–filler and filler–matrix. Figure 5 illustrates the trends of descending
Figure 3. Scanning electron microscope (SEM) micrograph of the 4 vol.% filler loading at 5 K
magnifications. (a) Polypropylene (PP), (b) PP/synthetic diamond (SND), (c) PP/boron nitride (BN),
(d) PP/copper (CU), and (e) PP/carbon nanotube (CNT).
632 Journal of Thermoplastic Composite Materials 26(5)
elongation at break with addition of stiff reinforcement, which decreases the ductility of
the matrix.
Thermal conductivity
Figure 6 presents the thermal conductivity of PP composites at room temperature. We
found that the thermal conductivity of composites increased monotonically from that of
PP and increased directly with increased filler amount. This ascending trend may be
attributed to the ease of heat transfer obtained by increasing contact in the composites.
CNT was the most effective filler for enhancing thermal conductivity, followed by SND,
Cu, and BN; this trend seems to follow the hierarchy of thermal conductivities of the
Young's modulus (GPa)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Weight fraction (%)
0
5
10
15
20
25
30
35
PP
PP/CNT
PP/SND
PP/BN
PP/CU
Filler loading (vol.%)
01234
Figure 4. Young’s modulus and weight fraction of polypropylene (PP) and PP composites as a
function of filler loading. Bar graph refers to the Young’s modulus and line plot refers to the weight
fraction, respectively.
Table 2. DSC and thermal interface resistance (R
i
) data for PP and PP composites filled at 4 vol.%
of CNT, SND, BN, and CU.
Composites X
c
(%) T
m
(C) T
c
(C) R
i
(nm
2
/w K)
PP 34.5 164.4 118.4 -
PP/CNT 30.0 163.9 123.7 0.98
PP/SND 38.7 163.9 124.3 0.14
PP/BN 42.4 164.0 125.8 1.3
PP/CU 33.9 163.9 120.7 1.1
BN: boron nitride, CNT: carbon nanotube, CU: copper, DSC: differential scanning calorimeter, PP:
polypropylene, SND: synthetic diamond.
Nurul and Mariatti 633
filler (refer to Table 1). The correlation with thermal interface resistance would influence
the effectiveness of the phonon to pass through in the composites systems. The thermal
resistance at the interface between the matrix and the filler, known as Kapitza resistance
(R
i
), was analyzed according to Eq. (1).
21
Elongation at break (%)
2
3
4
5
6
7
8
9
Filler loading (vol.%)
01234
PP
PP/CNT
PP/SND
PP/BN
PP/CU
Figure 5. Elongation atbreak of polypropylene (PP) and PP composites as a function of filler loading.
Thermal conductivity
(W/m.K)
0.22
0.24
0.26
0.28
0.30
0.32
0.34
0.36
PP/CNT
PP/SND
PP/BN
PP/CU
Filler loading (vol.%)
01234
Figure 6. Thermal conductivity of the polypropylene (PP) composites as a function of filler loading.
634 Journal of Thermoplastic Composite Materials 26(5)
Kc¼KmþKmL
2RiKfþLvf
3ð1Þ
where K
c
,K
m
,andK
f
are the thermal conductivity of the composite, matrix, and filler,
respectively; R
i
is the interfacial thermal resistance; Lis the length of filler assumed
at diameter d
50
;andv
f
is the volume fraction taken at 4 vol.%filler loading. The
predicted values of R
i
are summarized in Table 2. Lower thermal resistance was
exhibited by the SND and CNT systems due to their high thermal conductivity.
However, the CNT filler can produce higher thermal conductivities at identically lower
filler content due to its high aspect ratio, so that it is able to form a conductive network
for easier phonon-dominated ballistic heat transport compared with the spherical SND.
High R
i
was observed in the Cu and BN systems due to their low thermal conductivity.
However, the PP/Cu system exhibited minimum thermal conductivity at 2 vol.%load-
ing only, with decreasing values obtained with further addition of filler loadings. This
isrelatedtothepooradhesionandpoordispersionanddistributionofCuseeninSEM
morphology (Figure 3d). Variations in agglomeration size, high void content, and the
lack of contact between particles suggest that Cu particles were relatively nonhomo-
genously dispersed in the matrix. This subsequently resulted in low heat transfer in the
Cu system, which led to low thermal conductivity of the composite. In contrast, the
nearly uniform size of particles indicatinggooddispersioninthePPmatrix(Figure
3b, c, and e) resulted in better thermal interaction in CNT-, SND-, and BN-filled
PP composites.
Thermogravimetry analysis
The TGA curves for PP and PP composites at 4 vol.%filler loading are presented
in Figure 7. The curve shows single-step degradation where it shifted to the right
(i.e. higher temperature) with the addition of filler. This indicates that PP composites
achieve a stabilization effect through the barrier effect of filler loading, which hinders
volatilization of bulk samples into gas phase.
22
TGA curves reveal that composites
arestableatupto350
C, with weight reduction of around 0.5%. The TGA profile can
be clearly depicted by the derivative weight %(DTG) curve in Figure 8. The points
where degradation starts shifted to a higher temperature in composites compared
with PP. TGA trends of the composite materials are supported by the TGA analysis
of fillers (Figure 9), which revealed weight reduction in fillers as indicated by the
minus ()signintheyaxis as a function of temperature. CNT exhibited the highest
curve, suggesting that CNT has better thermal stability compared with the other
fillers. Weight reductions at different temperature (Table 3) follow the sequence of
CNT, SND, Cu, and BN. As shown in Figure 7, increasing filler loading leads to
increased thermal behavior of the composites due to the higher thermal stability of
fillers compared with the matrix. In general, all composite systems exhibited slightly
similar weight residue, which explains why fillers are retained without decomposition.
Most of the fillers will decompose at very high temperatures, while PP will be com-
pletely degraded.
Nurul and Mariatti 635
Conclusions
In this study, we performed characterization of fillers and investigation of the effect of
thermally conductive fillers on the mechanical, flow, and thermal properties of PP
composites. Findings suggest that CNT has better thermal properties compared with
Temperature (°C)
300 350 400 450 500 550
Weight loss (%)
0
20
40
60
80
100
PP
PP/CNT1
PP/CNT4
PP/SND4
PP/BN4
PP/CU4
Figure 7. Thermogravimetric analysis (TGA) curve of polypropylene (PP) and PP composites as a
function of temperature. The numbers 1 and 4 refer to 1 and 4 vol.% of filler loading, respectively.
Derivative weight %
(%/m)
–30
–20
–10
0
PP
PP/CNT1
PP/CNT4
PP/SND4
PP/BN4
PP/CU4
Temperature (°C)
350 400 450 500 550
Figure 8. Derivative weight percentage (DTG) of polypropylene (PP) and PP composites as a
function of temperature. The numbers 1 and 4 refer to 1 and 4 vol.% of filler loading.
636 Journal of Thermoplastic Composite Materials 26(5)
other conductive fillers. Results demonstrate that CNT, SND, BN, and Cu particles
variably affect the properties of PP composites. In general, the MFI of composites
decreased with increased filler loading due to the ability of fillers to hinder plastic flow.
PP/CNT exhibited the greatest thermal conductivity and thermal stability due to the high
aspect ratio of CNT, which facilitates the formation of bridges for phonon transformation
compared with the spherical fillers. However, entanglements of CNT lead to stress
concentration, resulting in reduced tensile properties. In general, the overall thermal
properties of composites improved with filler addition. For particulate fillers, lower d
50
results in higher tensile strength, Young’s modulus, higher R
i
, and lower thermal con-
ductivity values. The thermal conductivity and R
i
of the composite materials generally
seems to follow the hierarchy of thermal conductivities of the filler. Cu with the highest
d
50
showed poor thermal and tensile properties due to the agglomeration and voids which
0 200 400 600 800
Delta-M (mg)
–25
–20
–15
–10
–5
0
CNT
SND
BN
CU
Temperature (°C)
Figure 9. Thermogravimetric analysis (TGA) curve for conductive fillers used as a function of
temperature.
Table 3. Weight reduction (mg) in conductive fillers at 100 and 500C.
Conductive fillers
Weight reduction (mg)
At 100C At 500C
CNT 0.9 7.0
SND 1.7 8.6
CU 3.1 12.7
BN 4.0 13.2
BN: boron nitride, CNT: carbon nanotube, CU: copper, SND: synthetic diamond.
Nurul and Mariatti 637
existed in the system. PP/SND exhibited the greatest tensile strength possibly due to
better distribution of filler in the PP matrix.
Funding
This study was supported by Universiti Sains Malaysia under Postgraduate Research
Fund USM-RU-PGRS (Project no. 8033053) and Short Term Grant (Project no.
6035279).
References
1. Droval G, Glouannec P, Salagnac P, et al. Electrothermal behavior of conductive polymer
composite heating elements filled with ceramic particles. Vol. 22. Reston, VA, ETATS-UNIS:
American Institute of Aeronautics and Astronautics, 2008.
2. Kotsilkova R. Processing–structure–properties relationships of mechanically and thermally
enhanced smectite/epoxy nanocomposites. J Appl Polym Sci 2005; 97(6): 2499–2510.
3. Huang L, Zhan R and Lu Y. Mechanical properties and crystallization behavior of polypropy-
lene/nano-SiO
2
composites. J Reinf Plast Compos 2006; 25(9): 1001–1012.
4. Kochetov R, Andritsch T, Lafont U, Morshuis PHF, Picken SJ and Smit JJ. Preparation and
dielectric properties of epoxy–BN and epoxy–AlN nanocomposites. IEEE Electr Insul Conf
2009: 397–400.
5. Sofian NM, Rusu M, Neagu R and Neagu E. Metal powder-filled polyethylene composites. V.
thermal properties. J Thermoplast Compos Mater 2001; 14(1): 20–33.
6. Gu J, Zhang Q, Dang J, Zhang J and Yang Z. Thermal conductivity and mechanical properties
of aluminum nitride filled linear low-density polyethylene composites. Polym Eng Sci 2009;
49(5): 1030–1034.
7. Zhao Y-Q, Lau K-T, Kim J-K, Xu C-L, Zhao D-D and Li H-L. Nanodiamond/poly (lactic
acid) nanocomposites: effect of nanodiamond on structure and properties of poly (lactic acid).
Compos B Eng 41(8): 646–653.
8. Jung J, Kim J, Uhm YR, Jeon J-K, Lee S, Lee HM, et al. Preparations and thermal properties
of micro- and nano-BN dispersed HDPE composites. Thermochim Acta 2010; 499(1-2): 8–14.
9. Boudenne A, Ibos L, Fois M, Majeste´ JC and Ge´ hin E. Electrical and thermal behavior of
polypropylene filled with copper particles. Compos A Appl Sci Manuf 2005; 36(11):
1545–1554.
10. Wu CL, Zhang MQ, Rong MZ and Friedrich K. Tensile performance improvement of low
nanoparticles filled-polypropylene composites. Compos Sci Technol 2002; 62(10-11):
1327–1340.
11. Logakis E, Pollatos E, Pandis C, Peoglos V, Zuburtikudis I, Delides CG, et al. Structure–prop-
erty relationships in isotactic polypropylene/multi-walled carbon nanotubes nanocomposites.
Compos Sci Technol 2010; 70(2): 328–335.
12. Chan KL, Mariatti M, Lockman Z and Sim LS. Effects of the size and filler loading on the
properties of copper- and silver-nanoparticle-filled epoxy composites. J Appl Polym Sci
2010; 121(6): 3145–3152.
13. Muric-Nesic J, Compston P and Stachurski ZH. On the void reduction mechanisms in vibra-
tion assisted consolidation of fibre reinforced polymer composites. Compos A Appl Sci Manuf
2010; 42(3): 320–327.
14. Liu L, Zhang B-M, Wang D-F and Wu Z-J. Effects of cure cycles on void content and mechan-
ical properties of composite laminates. Compos Struct 2006; 73(3): 303–309.
638 Journal of Thermoplastic Composite Materials 26(5)
15. Naganuma T, Naito K, Kyono J and Kagawa Y. Influence of prepreg conditions on the
void occurrence and tensile properties of woven glass fiber-reinforced polyimide composites.
Compos Sci Technol 2009; 69(14): 2428–2433.
16. Rutz BH and Berg JC. A review of the feasibility of lightening structural polymeric compo-
sites with voids without compromising mechanical properties. Adv Colloid Interface Sci 2010;
160(1-2): 56–75.
17. Hartikainen J, Hine P, Szabo´ JS, Lindner M, Harmia T, Duckett RA, et al. Polypropylene
hybrid composites reinforced with long glass fibres and particulate filler. Compos Sci Technol
2005; 65(2): 257–267.
18. Nurazreena, Hussain LB, Ismail H and Mariatti M. Metal filled high density polyethylene
composites—electrical and tensile properties. J Thermoplast Compos Mater 2006; 19(4):
413–425.
19. Zhao Y-Q, Lau K-T, Kim J-K, Xu C-L, Zhao D-D and Li H-L. Nanodiamond/poly (lactic
acid) nanocomposites: Effect of nanodiamond on structure and properties of poly (lactic acid).
Compos B Eng 2010; 41(8): 646–653.
20. Kang CH, Yoon KH, Park Y-B, Lee D-Y and Jeong S-S. Properties of polypropylene compo-
sites containing aluminum/multi-walled carbon nanotubes. Compos A Appl Sci Manuf 2010;
41(47): 919–926.
21. Razavi-Nouri M, Ghorbanzadeh-Ahangari M, Fereidoon A and Jahanshahi M. Effect of car-
bon nanotubes content on crystallization kinetics and morphology of polypropylene. Polym
Test 2009; 28(1): 46–52.
22. Mukhopadhyay A, Otieno G, Chu BTT, Wallwork A, Green MLH and Todd RI. Thermal and
electrical properties of aluminoborosilicate glass-ceramics containing multiwalled carbon
nanotubes. Scripta Mater 2011; 65(5): 408–411.
Nurul and Mariatti 639
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... Kajian oleh Sabri et al. (2012) yang menggunakan bahan aluminium 6061 membuktikan apabila kekonduksian elektrik bahan berkurang menjadi 1-2 S/m dengan kehadiran kakisan pada sampel semasa proses berlaku. Oleh itu, bahan alternatif yang berunsur karbon iaitu grafit, grafin, tiub nanokarbon, serta komposit yang mempunyai sifat rintangan tinggi terhadap kakisan menjadi perhatian dalam penyelidikan (Nurul & Mariatti 2013). Kajian lepas menunjukkan penggunaan bahan polimer komposit seperti polipropilena diperkuat gentian karbon, epoksi diperkuat karbon hitam, dan epoksi diberkuat gentian karbon, mempunyai sifat rintangan kakisan yang baik, kekuatan dan ketegangan yang tinggi serta produk yang ringan (ketumpatan kurang 2.5g/cm 3 ) telah menjadi alternatif sebagai bahan konduktif (Lima et al. 2020;Rajak et al. 2019;Sabri et al. 2012). ...
... Namun begitu, kajian lepas menunjukkan dengan penambahan pengisi yang lebih tinggi (melebihi 50 bt.%) telah menyebabkan penurunan dalam kekonduksian terma yang disebabkan oleh lekatan yang lemah dengan penyebaran dan pengedaran pengisi yang kurang baik (Nurul & Mariatti 2013). Teori perkolasi diguna pakai dalam aplikasi peranti elektronik untuk menerangkan kebarangkalian pengisi konduktif dalam polimer untuk membentuk jalur aliran elektron yang bersambung. ...
... Peningkatan RAJAH 1. Kesan penambahan kandungan grafit kepada kekonduksian elektrik (Liao et al. 2008) kandungan grafit melebihi 77 bt.% telah meningkatkan kekonduksian melebihi 100 S cm -1 . Peningkatan kekonduksian elektrik memberi kesan yang baik apabila ia dapat mewujudkan jalan konduktif elektrik yang lebih banyak untuk menyediakan aliran pembawa arus (Nurul & Mariatti 2013). ...
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Penambahan kandungan pengisi polimer komposit dapat meningkatkan kekonduksian elektrik dan terma yang baik, serta mempunyai kekuatan tegangan dan modulus yang tinggi telah memperluaskan aplikasi dalam industri peranti elektronik. Walau bagaimanapun, penambahan kandungan pengisi yang kurang daripada 20 bt.% akan mengakibatkan ketidaksempurnaan dalam penyebaran serta terdapat gumpalan pengisi ke dalam komposit. Ulasan kajian ini adalah untuk mengenal pasti pengaruh penambahan kandungan pengisi bagi bahan konduktif polimer komposit menggunakan percetakan 3D terhadap sifat elektrik, terma dan mekanikal. Ulasan ini merangkumi penggunaan bahan konduktif polimer komposit yang dibentuk melalui kaedah Pemodelan Pemendapan Bersatu (FDM) yang merupakan salah satu daripada percetakan 3D. Proses percetakan 3D yang dilapisi oleh lapisan demi lapisan akan menghasilkan struktur objek yang kompleks serta proses pembuatan yang cepat telah memberi sumbangan kepada penghasilan konduktif polimer komposit. Kekonduksian elektrik dapat ditingkatkan dengan penambahan kandungan pengisi sehingga 50 bt.%. Selain itu, penambahan kandungan pengisi yang dapat menawarkan permukaan yang lebih berkesan antara permukaan pengisi dan matriks telah meningkatkan suhu penghabluran (Tc) dan suhu puncak penghabluran (Tp) dalam sifat terma serta nilai kekuatan tegangan dan modulus dalam sifat mekanik. Penambahan kandungan pengisi polimer komposit sehingga 50 bt.% dapat meningkatkan kesesuaian bahan untuk digunakan pada peranti elektronik.
... It is known [34] that polymers' MFIs usually decrease with an increase in the mass fraction of fillers in the polymer matrix. The decrease in the MFI of the filled PETG-filament compared to the initial one is most (Table 2). ...
... However, the general enhancement in thermal stability of the of nanocomposites can be credited to the good dispersion and interaction between the polymer matrix and the reinforcement phases as represented by the SEM micrograph in Figure 3 (Li et al., 2017). Since the BN and CNTs nanoparticles have good thermal stability as shown in Figure 5A, they offered thermal barriers in the matrix of the polymer, which slowed down the degradation of the nanocomposites (Nurul and Mariatti, 2013). In addition, the CNTs and BN have good capability of mechanically interlocking of the PVDF chains and restrict the flow of the chains on the application of heat, leading to improved thermal stability of the nanocomposites (Chu et al., 2012). ...
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Most polymer materials are thermal and electrical insulators, which have wide potential in advanced energy-power applications including energy conversion. However, polymers get softened when in contact with heat, which causes their molecular chains to flow as the temperature increases. Although polymer dielectrics exhibit high power density, they face challenges of low energy density which is due to the low dielectric permittivity associated with them. Therefore, this study tried to address the poor thermal energy management and low energy density of poly (vinylidene fluoride) (PVDF) while maintaining its flexible property using low content of hybrid carbon nanotubes (CNTs–0.05wt%, 0.1wt%) and boron nitride (BN–5wt%, 10wt%) nano-reinforcements. The nanocomposites were developed through solvent mixing and hot compression processes. The dielectric constant increased from 9.1 for the pure PVDF to 42.8 with a low loss of about 0.1 at 100 Hz for PVDF-0.1wt%CNTs-10wt%BN. The thermal stability of the nanocomposites was enhanced by 55°C compared to the pure PVDF. The nanocomposites also showed improved melting and crystallization temperatures. The developed PVDF-CNTs-BN nanocomposites showed significant enhancements in thermal energy management, stability, and dielectric properties. The significantly improved properties are credited to the synergetic effects between CNTs and BN in the PVDF matrix in promoting homogeneous dispersion, thermal barrier, interfacial polarization/bonding, insulative and conductive properties. Therefore, the developed nanomaterials in this study can find advanced applications in the energy-power sector owing to their enhanced performances.
... In the second stage, a farther increase in MCC charge more than 7% caused a decrease in PLA composites MFI. According to Jaafar et al., this behavior is due to the strong molecular interaction between MCC molecules (Nurul and Mariatti, 2018). Similar results were reported in Polypropylene composites reinforced with treated and non-treated flax fiber (Soleimani and Tabil, 2008). ...
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The potential of ecofriendly biochar, a carbon-rich byproduct of biomass pyrolysis, as a low-cost solid lubricating filler for low-density polyethylene (LDPE) sustainable biocomposites is investigated in this work. Tensile strength, hardness, thermogravimetric analysis (TGA), melting flow index (MFI), tensile test, flexural test, and frictional tests were used to characterize the biocomposites’ mechanical, thermal, and tribological properties. Energy-dispersive X-ray spectroscopy (EDS) was used to assess the chemical composition of the biochar, while field-emission scanning electron microscopy (FESEM) was used to capture the biochar morphology. The results showed that the incorporation of biochar in LDPE matrix increased the mechanical characteristics of the biocomposites and resulted in a significant increase in tensile strength, flexural strength, and hardness. More specifically, the LDPE+10 wt% composite outperformed the pure LDPE matrix by 1.9% in tensile strength and 47% in flexural strength. Furthermore, integrating biochar into LDPE composites enhances thermal stability, lowers the melt flow index (MFI), and boosts the hardness by 24.3% for the composite with 10% biochar content. Furthermore, biochar improves wear resistance and durability, with the LDPE10 composite exhibiting a friction coefficient that is 56.3% lower than pure LDPE. These findings indicate that biochar is a viable, cost-effective, and environmentally friendly filler for improving the performance of LDPE-based biocomposites for many varieties of applications.
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Polylactic acid (PLA) has increasingly attracted studies in various industrial fields due to its great biocompatibility and sustainability over other thermoplastics, which are widely used as filament feedstock in 3D-printing technology, specifically in Fused Deposition Modelling (FDM). Despite PLA being suitable in FDM processing, it has limitations in applications that requires plastic deformation at high-stress levels due to its low strength and ductility. For this purpose, this review article discusses the existing studies that involve the incorporation of fillers in 3D-printed polylactic acid to maximize its functionality, which is non-attainable by the pure filament material alone. An overview of polylactic acid in FDM and the properties and effects of functional fillers of different types are presented. Finally, a complete table of which functional fillers are categorized (carbonaceous, metallic, ceramic and glassy, plant-based, and mineral) summarizes the reported comparison of 3D-printed pure PLA and the composite, scoping to reveal the mechanical modifications of each filler.
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Thermal properties—such as thermal conductivity, thermal diffusivity, and specific heat—of metal (copper, zinc, iron, and bronze) powder-filled high-density polyethylene composites are investigated experimentally in the range of filler content 0-24% by volume. Experimental results show a region of low particle content, 0-16% by volume, where the particles are distributed homogeneously in the polymer matrix and do not interact with each other. In this region most of the thermal conductivity models for two-phase systems are applicable. At higher particle content, the filler tends to form agglomerates and conductive chains resulting in a rapid increase in thermal conductivity.
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The electrical resistivity and tensile properties of composites formed by the incorporation of metal powders such as aluminum (Al), copper (Cu), and iron (Fe) in a high-density polyethylene (HDPE) matrix are investigated. Results are presented for metal fillers content varying between 0 and 55% by volume. The effect of different types of filler and filler content on electrical and tensile properties of the composites is analyzed. As a result, it is found that the electrical resistivity properties of the composites are governed by the shape of the filler and the amount of filler content. In this study, it is found that the tensile strength is influenced by the shape of the filler, degree of crystallinity and the adhesion between metal fillers and polymer. For example, more metal filler loading results in filler agglomeration which reduces the adhesion between metal fillers and polymer and increases the metal-to-metal contacts, this subsequently reduces the strength of the composite materials. The Young's modulus of the composite systems seems to follow the normal trend of filled polymer composites, where in general the Young's modulus increases with increasing amount of filler loadings.
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In this study, polypropylene (PP)/nano-silica (nano-SiO2) composites were prepared by a melt blending process. Here, a novel surface treatment method which uses combined dispersant and a coupling agent is developed to treat the nano-SiO2 which is uniformly dispersed into the PP matrix. To treat the surface of nano-SiO2, the optimal content of the dispersant (SDBS) is 2.0% and the optimal amount of the coupling agent (KH-550) is 1.5%. The mechanism and synergistic effect of the combined dispersant and coupling agent are discussed based on their chemical structures. The fractography of PP/nano-SiO2 composites after notched impact testing observed by the scanning electron microscope (SEM) proves the uniform dispersion of nano-SiO2 in the PP phase. The mechanical testing results show that after surface treatment, both the tensile and notched impact strength of nanocomposites enhance markedly. The tensile strength reaches its maximum with the 4.0% of nano-SiO2 and the notched impact toughness achieves its maximum with the 5.0% of nano-SiO2. The crystallization behavior characterized by the differential scanning calorimetry (DSC) and the crystalline structure observed by the polarizing microscope (PM) indicated that nano-SiO2 has a nucleation role in the crystallization of PP which results in a higher crystallization temperature, a higher degree of crystallinity, and a smaller size of spherulites.
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We report the effects of multiwalled carbon nanotube (MWCNT) dispersions (<= 15 wt.%) on the electrical and thermal conductivities of an aluminoborosilicate glass-ceramic. The electrical conductivity was improved by a factor of similar to 10(6) and the thermal conductivity by similar to 70%. The uniform MWCNT distribution achieved with up to 10 wt.% MWCNT resulted in a relatively high electrical percolation threshold. Thermal conductivity was limited by the low thermal conductivities of the CVD MWCNTs, length reduction during processing and interfacial resistance.
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The thermal properties of micro-sized boron nitride (BN) and nano-sized BN dispersed high density polyethylene (HDPE) composites were investigated by means of differential scanning calorimetry (DSC) and thermo-gravimetric analysis (TGA). Nano-BN powder was prepared by using a ball mill process before it was mixed in HDPE. To enhance the dispersivity of nano-BN in the polymer matrix, the surfaces of the nano-particles were treated with low density polyethylene (LDPE) which was dissolved in the cyclohexane solvent. The average particle sizes of micro-BN powder and LDPE coated nano-BN powder were ∼10 μm and ∼100 nm respectively. Dispersion and distribution of 5 wt% and 20 wt% of micro-BN and nano-BN respectively mixed in HDPE were observed by using the scanning electron microscope (SEM). According to the thermal analyses of pure HDPE, micro-BN/HDPE, and nano-BN/HDPE, 20 wt% nano-BN/HDPE composite shows the lowest enthalpy of fusion (ΔHm) and better thermal conductive characteristics compared to the others.
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Nanodiamond (ND)/poly (lactic acid) (PLA) nanocomposites with potential for biological and biomedical applications were prepared by using melting compound methods. By means of transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric analyses (TGA), Dynamic mechanical analyses (DMA), Differential scanning calorimetry (DSC) and Tensile test, the ND/PLA nanocomposites were investigated, and thus the effect of ND on the structural, thermal and mechanical properties of polymer matrix was demonstrated for the first time. Experimental results showed that the mechanical properties and thermal stability of PLA matrix were significantly improved, as ND was incorporated into the PLA matrix. For example, the storage modulus (E′) of 3wt% ND/PLA nanocomposites was 0.7GPa at 130°C which was 75% higher than that of neat PLA, and the initial thermal decomposition was delayed 10.1°C for 1wt% ND/PLA nanocomposites compared with the neat PLA. These improvements could be ascribed to the outstanding physical properties of ND, homogeneous dispersion of ND nanoclusters, unique ND bridge morphology and good adhesion between PLA matrix and ND in the ND/PLA nanocomposites.
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Thermoplastic nanocomposites were prepared in a laboratory mixer using polypropylene (PP) and different amounts of single-walled carbon nanotubes (SWNT) in the range 0.25–2wt%. The effect of SWNT content on the thermal and mechanical properties and also morphology of the PP/SWNT nanocomposites were studied. The results obtained from nonisothermal crystallization of PP and the nanocomposites, which were carried out using the differential scanning calorimetry technique, showed that not only the overall rate of crystallization of PP increased when SWNT was added to the polymer but also the rate of nucleation was higher and the crystallite size distribution was more uniform for the nanocomposites than for PP. From the optical microscopy studies, it was found that the PP spherulites decreased in size when SWNT was introduced into the polymer and also the mature spherical shaped crystals of PP changed in part to the immature kidney- or bean-shaped crystal forms in the nanocomposites. In addition, the crystallization kinetics was also studied by using isothermal spherulitic growth rate, and the values of nucleation constant, Kg, and end surface free energy, σe, were calculated for PP and the nanocomposites according to Lauritzen–Hoffman theory. The reductions of these two parameters were in agreement with the fact that the rate of crystallization of PP in nanocomposites was higher than that of the pristine polymer.
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Structure and fracture behaviour of long glass fibre (LGF) reinforced polypropylene (LGF PP) composites including calcium carbonate (CaCO3) as a filler were studied. Fibre orientation, fibre length distribution and mechanical properties of LGF PP/CaCO3 hybrid composites, as well as the crystallinity changes of polypropylene upon filler addition are reported. Furthermore, an acoustic emission (AE) analysis was applied to the fracture mechanical test, in order to get information about the fracture modes during the loading. It was found out that the filler addition had little effect on the fibre orientation and crystallisation behaviour of LGF PP, but the average fibre length decreased. AE analysis showed that the addition of filler caused early stage debonding of the LGFs, when the samples were subjected to low speed tensile loading (1 mm/min). These observations may explain the changes of the mechanical properties of LGF PP upon filler addition.
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Polypropylene/aluminum–multi-walled carbon nanotube (PP/Al–CNT) composites were prepared by a twin-screw extruder. The morphology indicates that the CNTs are well embedded or implanted within Al-flakes rather than attached on the surface. During preparation of composites, the CNTs came apart from Al–CNT so that free CNTs as well as Al–CNT were observed in PP/Al–CNT composite. The crystallization temperatures of PP/CNT and PP/Al–CNT composites were increased from 111°C for PP to 127°C for the composites. The decomposition temperature increased by 55°C for PP/CNT composite and 75°C for PP/Al–CNT composite. The PP/Al–CNT composite showed higher thermal conductivity than PP/CNT and PP/Al-flake composites with increasing filler content. PP/Al–CNT composites showed the viscosity values between PP/CNT and PP/Al-flake composites. PP/Al–CNT composite showed higher tensile modulus and lower tensile strength with increasing filler content compared to PP/CNT and PP/Al-flake composites.