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Recycled PCB flour reinforced linear low-density polyethylene composites enhanced by water cross-linking reaction.

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ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING
Asia-Pac. J. Chem. Eng. 2009; 4: 169–177
Published online 22 September 2008 in Wiley InterScience
(www.interscience.wiley.com) DOI:10.1002/apj.191
Special Theme Research Article
Recycled PCB flour reinforced linear low-density
polyethylene composites enhanced by water
cross-linking reaction
Chen-Feng Kuan,1 * Hsu-Chiang Kuan,1 Chen-Chi M. Ma,2 Chia-Hsun Chen,1 Kun-Chang Lin1 and Hsin-Chin Peng1
1
2
Department of Computer Application Engineering, Far East University, Tainan, Taiwan
Department of Chemical Engineering, National Tsing Hua University, Hsin-Chu, Taiwan
Received 2 May 2008; Revised 9 June 2008; Accepted 15 July 2008
ABSTRACT: Recycled printed circuit board (PCB) flour reinforced linear low-density polyethylene (LLDPE) composites were prepared successfully. Water cross-linking technique was adopted to improve the physical characteristics
of the composites. Composites were compounded using a twin-screw extruder and treated with a coupling agent
(vinyltrimethoxysilane, VTMOS) and a compatibilizer (polyolefin elastomer grafted with melaic acid, POE-g-MA).
They were then moisture-cross-linked in hot water. The composite that was cross-linked in water exhibited better
mechanical properties than the noncross-linked composite because of strong chemical bonding between the filler and
the polyolefin matrix. When the PCB flour content reaches 60 wt% following 4 h of water cross-linking, the tensile
strength and the flexural strength are increased by 18.8% (12.8–15.2 MPa) and 13.2% (21.9–24.8 MPa) respectively.
Scanning electron microscopy (SEM) images of the fracture surfaces of water cross-linked composites indicated that
good interfacial strength existed between the filler and the polyolefin matrix. Thermal analyses of water cross-linked
composites indicated that the thermal degradation temperature and the heat deflection temperature (HDT) of the composite increased with the increasing of water cross-linking time. The HDT of the composite rose from 55.8 to 83 ◦ C.
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
KEYWORDS: PCB flour; linear low-density polyethylene; water cross-linking; coupling agent; compatibilizer;
mechanical property
INTRODUCTION
Recycling of wastes of electrical and electronic equipments (WEEE) is foreseen in the new European (EU)
Directive.The WEEE Directive is based on the experience of a few European countries. The organizations
managing voluntary take back systems on behalf of
the electrical and electronic equipment (EEE) producers
have been responsible for the collection and recycling
of the WEEE. The treatment of plastics will be encouraged as a consequence of the implementation of both the
landfill directive (ban on dumping high calorific value
waste plastic) and the incineration directive, which
encourages handling (incineration) high calorific waste
for energy recovery.[1] Copper-clad laminate (CCL) is
a basic component in the EEE. The reuse of CCL plays
an important role in the recycling of WEEE.[2]
Printed circuit board (PCB) flour is generally prepared from phenolic cellulose paper or glass fiber cloth
*Correspondence to: Chen-Feng Kuan, Department of Computer
Application Engineering, Far East University, 744, Tainan, Taiwan.
E-mail: cfkuan@cc.feu.edu.tw
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
copper-clad laminates after removing all the metal.
Adding PCB flour to thermoplastic resins can produce
composite materials with increased strength and stiffness. Owing to the different characteristics of the polyolefin matrix and filler, both the filler and polymeric
matrix have to be chemically modified to improve the
interfacial compatibilization. Adding a suitable interface
modifier will promote the stability of the morphology in
incompatible polymer–fiber composites.[3] Such modifiers improve the composite morphology by dispersing
more finely the discontinuous filler or fiber in the dominant polymer matrix. In the present work, silane coupling agent and polyolefin elastomer grafted with melaic
acid (POE-g-MA) compatibilizer are used as interface
modifiers, which are chemically bonded to both the
PCB flour and the polymer matrix.[4,5] A strong interfacial adhesion between the reinforcement and the matrix
is extremely important to develop polymer composites
with improved physical and mechanical properties.
Cross-linking with water is achieved by grafting
polyethylene with silane followed by hydrolysis to
Si–OH groups and subsequent condensation to form
170
C.-F. KUAN ET AL.
Si–O–Si bonds.[6] This process is through free radical initiators which can subsequently condense in
water, leading to the formation of cross-linking.[7]
Cross-linked polyethylene has become widely adapted
for a number of industrial applications. Cross-linking
of polyethylene molecules into three-dimensional networks leads to improvement of material properties such
as impact strength, chemical resistance, and thermal
characteristics.[8]
The purpose of this study is to investigate the effects
of various cross-linking times on the mechanical properties of the recycled PCB flour/linear low density
polyethylene (LLDPE) composite. Since this composite is usually used outdoor and under the environmental
aging conditions, sunlight and moisture would further
promote the water cross-linking reaction of the recycled PCB flour/LLDPE composite and consequently,
improve some physical properties of this composite.
The thermal degradation properties and the heat deflection temperature (HDT) of water cross-linked recycled
PCB flour/LLDPE composite were also investigated in
this study.
EXPERIMENTAL PROCEDURES
Materials
LLDPE with a melt index of 2.0 was supplied by
the Taiwan Polymer Corporation, Taiwan. No.LL120.
Recycled PCB flour was from Chang Chun Petrochemical Co., Taiwan. It was prepared from phenolic cellulose paper copper-clad laminates after removing all
the metal and pulverizing to the recycled PCB flour
size of 80–100 mesh. Vinyltrimethoxysilane (VTMOS),
No.Q9-6300 was produced by Dow Corning company
and POE-g-MA was from Ray Sheng Plastics Co., Taiwan. The grafting ratio of MA was 0.6 wt%. Dicumyl
peroxide (DCP), No. PEROXIMON DC, was supplied
by ELF ATOCHOEM, France. Di-n-butyltin dilaurate
(DBTDL), No.T12, supplied by Air Products Co., USA
was used as a catalyst to accelerate the water crosslinking reaction.
Sample preparation
PCB flour was dried in an air oven at 100 ◦ C for 4 h,
until the moisture content was below 1.0 wt%. It was
then treated with VTMOS silane coupling agent 2 phr
(part per hundred parts of resin) by surface treatment
and 0.2 phr DCP and 0.15 phr T12 DBTDL were mixed
by a Hancel mixer. It was then mixed with LLDPE and
POE-g-MA (5 phr) pellets in a plasticizing extruder.
The extruder is a twin-screw co-rotating type extruder;
with L/D = 43.5, and a high shear rate configuration.
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Asia-Pacific Journal of Chemical Engineering
A gravimetric feeder and side stuffer were used for
loading the PCB flour. Vacuum was used during the
extrusion process. The rotation speed was 80 rpm and
barrel temperatures were 100, 115, 130, 135,145, 160,
170, 155, 145, 140 and 140 ◦ C (primary feed) to the exit
die. The extruded material was cut into small pellets in
a granulator. Dumb-bell-shaped specimens were then
injection moulded using a Battenfeld, Ba750 CDPLUS
injection moulding machine at a mould temperature of
160–190 ◦ C. The maximum injection pressure was 100
bars and the hold pressure was 10 bars.
Some of the specimens were subsequently subjected
to water cross-linking at different cross-linking times.
They were placed in an isothermal water bath at 70 ◦ C
for 0.5, 1, 2, and 4 h for the water cross-linking reaction
to take place.
Property measurement
Fourier transform infrared (FTIR) spectra of PCB flour
reinforced LLDPE composites were recorded between
400 and 4000 cm−1 with a Nicolet Avatar 320 FTIR
spectrometer, Nicolet Instrument Corporation, Madison,
WI, USA. Samples were placed on the ATR (Attenuated
Total Reflectance) attachment and a minimum of 32
scans were averaged with a resolution of 2 cm−1
within the 400–4000 cm−1 range. The characteristic
absorption peaks of the functional group were detected
and monitored during the water cross-linking reaction.
The mechanical properties of dumb-bell-shaped specimens were measured on an Instron Model 4468
machine. Tensile test procedures followed the ASTM
D638-98 method[9] with a crosshead speed 20 mm/min.
The dimensions of the samples were 25.0 mm ×
10.0 mm × 1.4 mm (length × width × thickness). Six
specimens were tested in each case. Flexural tests
were done following the ASTM D790-98 method[10]
with a span-to-depth ratio of 40 and crosshead speed
of 1.0 mm/min. Notched impact strength was tested
according to ASTM D256-97 method[11] and a TMI
testing machine (TMI Co. USA.) was used [the dimensions of these samples were 63.0 mm × 12.7 mm ×
3.2 mm (length × width × thickness)]. All tests were
performed at an ambient temperature of 25 ± 2 ◦ C.
Notched impact fractured surfaces of the composites
were used for scanning electron microscope (SEM)
studies using a TOPCON microscope (Model SM-300,
Japan). The fractured surfaces were sputter-coated with
gold prior to scanning.
HDT was measured by a TOYOSEIKI S-6M HDT
tester following the ASTM D648-98C method.[12] The
loading pressure was 4.6 kgf/cm2 , and the heating rate
was 120 K/h.
Thermo-oxidative degradation of these composites
was measured by a TGA (Thermogravimetric Analyzer)
instrument (Du-Pont-951) from room temperature to
Asia-Pac. J. Chem. Eng. 2009; 4: 169–177
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
RECYCLED PCB FLOUR REINFORCED LLDPE COMPOSITES
◦
700 C at a heating rate of 10 K/min in air. The
measurements were conducted using 6–10 mg samples.
Weight-loss vs temperature curves were recorded.
introduced into the main chain of LLDPE during grafting. Therefore, an increase in the water cross-linking
time increases the number of –CH2 CH2 Si–O–Si bonds
on the LLDPE main chain.[13,14]
RESULTS AND DISCUSSION
Tensile properties
FTIR spectroscopic analysis
Figure 2(a) presents the tensile strengths of PCB flour
reinforced LLDPE composites with and without a silane
coupling agent and compatibilizer treatment. Composites with high PCB flour content, which were treated
with interface modifiers had better tensile strengths
than the untreated ones. The tensile strength of pristine
PCB flour reinforced LLDPE composites decreases as
the PCB flour content is increased. A composite with
60 wt% PCB flour content and an interface modifier
(coupling agent and compatibilizer) has a 25.2% higher
tensile strength than the other composite.
Figure 1(a), (b), and (c) presents the FTIR spectra for
40, 50, and 60 wt% PCB flour reinforced composites, respectively for various water cross-linking reaction times. The spectra are shifted vertically for clarity. Changes in IR absorption peak heights are well
known to be caused by actual changes in the chemical composition of the composite. The figures display
the absorbance band appearing at 1580 cm−1 , which is
apparently associated with R–CH2 –R bonds that are
(b)
40wt% 0 hr
Stacked Transmittance
Stacked Transmittance
(a)
40wt% 0.5 hr
40wt% 1.0 hr
40wt% 2.0 hr
40wt% 4.0 hr
4000
3500
3000
2500
2000
Wave number
1500
1000
500
50wt% 0 hr
50wt% 0.5 hr
50wt% 1.0 hr
50wt% 2.0 hr
50wt% 4.0 hr
4000
3500
3000
(cm-1)
2500
2000
Wave number
1500
1000
500
(cm-1)
Stacked Transmittance
(c)
LLDPE
60wt% 0 hr
60wt% 0.5 hr
60wt% 1.0 hr
60wt% 2.0 hr
60wt% 4.0 hr
2000
1800
1600
1400
1200
1000
Wave number (cm-1)
Figure 1. (a) FTIR Spectra of 40 wt% wood fiber reinforced LLDPE composites for various water cross-linking times
(b) FTIR spectra of 50 wt% wood fiber reinforced LLDPE composites for various water cross-linking times (c) FTIR
spectra of 60 wt% wood fiber reinforced LLDPE composites for various water cross-linking times. This figure is
available in colour online at www.apjChemEng.com.
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Asia-Pac. J. Chem. Eng. 2009; 4: 169–177
DOI: 10.1002/apj
171
C.-F. KUAN ET AL.
17
16.0
15.5
15
Tensile Strength (MPa)
Tensile Strength (MPa)
Asia-Pacific Journal of Chemical Engineering
Without Treatment
With Silane Treatment
With Silane & Compatilizer
16
14
13
12
11
10
9
15.0
14.5
14.0
13.5
40 %
50 %
60 %
13.0
12.5
8
7
12.0
0
10
(a)
20
30
40
50
60
0
(b)
PCB Flour Content (wt%)
1
2
3
Water-Crosslinking Time (hr)
4
600
15.0
Without Silane Treatment
With Silane Treatment
With Silane & Compatibilizer
400
300
200
100
Tensile Elongation (%)
500
Tensile Elongation (%)
172
0
12.5
10.0
7.5
5.0
2.5
0
(c)
40 %
50 %
60 %
10
20
30
40
PCB Flour Content (wt%)
50
60
0.0
(d)
0.5
1.0 1.5 2.0 2.5 3.0 3.5
Water-Crosslinking Time (hr)
4.0
4.5
Figure 2. (a) Comparison of the tensile strength of PCB flour reinforced LLDPE composites with various PCB flour contents
and various treatment methods; (b) Tensile strength of silane-treated PCB flour reinforced LLDPE composites with various
PCB flour contents for various water cross-linking times; (c) Comparison of the tensile elongation of PCB flour reinforced
LLDPE composites with various PCB flour contents and various treatment methods; (d) Tensile elongation of silane-treated
PCB flour reinforced LLDPE composites with various PCB flour contents for various water cross-linking times. This figure is
available in colour online at www.apjChemEng.com.
Figure 2(b) shows the plotting of the tensile strength
of PCB flour reinforced LLDPE composites with 40,
50, and 60 wt% PCB flour contents for various water
cross-linking periods. Composites that had undergone a
water cross-linking reaction had better tensile strength
than the untreated ones (after 4 h of water cross-linking
treatment, the tensile strength of 60 wt% pristine PCB
flour composite increased from 12.8 to 15.2 MPa, or by
an 18.8% increase). The increase in tensile strength is
associated with the formation of cross-linking network
between the filler and the polymer matrix (LLDPE
polymer chains). The results suggest that modifying the
polymer or filler surface can enhance the compatibility
of polymer and filler. Increasing the water cross-linking
time improves the tensile strength of the PCB flour
composite.
The results of tensile elongation are plotted in
Figure 2(c) and (d). Although the silane coupling agent,
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
compatibilizer treatment, and water cross-linking reaction improved the tensile strength of the composite, the
tensile elongation property of the composite is reduced
because of the cross-linking network (chemical bonding) between the flexible LLDPE matrix and the stiff
PCB flour or among the LLDPE intermolecular chains.
The results also reveal that POE-g-MA compatibilizer
treatment slightly increases the tensile elongation of a
composite.
Flexural characteristics
Figure 3(a)–(d) shows the plotting of the flexural
strength and flexural modulus of PCB flour reinforced
LLDPE composites with PCB flour contents of 40, 50,
and 60 wt%, and for various water cross-linking periods. Composites with high PCB flour content that had
Asia-Pac. J. Chem. Eng. 2009; 4: 169–177
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
RECYCLED PCB FLOUR REINFORCED LLDPE COMPOSITES
27.5
25
Without Treatment
With Silane Treatment
With Silane & Compatibilizer
22.5
Flexural Strength (MPa)
Flexural Strength (MPa)
25.0
20.0
17.5
15.0
12.5
24
23
22
21
20
10.0
19
0
10
20
30
40
50
60
PCB Flour Content (wt%)
(a)
0
1
2
3
Water-Crosslinking Time (hr)
(b)
4
1.2
1100
40 %
50 %
60 %
1.1
1000
Without Treatment
With Silane Treatment
With Silane & Compatibilizer
900
Flexural Modulus (GPa)
Flexural Modulus (MPa)
40%
50%
60%
800
700
600
1.0
0.9
0.8
0.7
500
0.6
400
0.5
40
(c)
45
50
55
PCB Flour Content (wt%)
0
60
(d)
1
2
3
4
Water-Crosslinking Time (hr)
Figure 3. (a) Comparison of the flexural strength of PCB flour reinforced LLDPE composites with various PCB
flour contents and various treatment methods; (b) Flexural strength of silane-treated PCB flour reinforced LLDPE
composites with various PCB flour contents for various water cross-linking times.; (c) Comparison of the flexural
modulus of PCB flour reinforced LLDPE composites with various PCB flour contents and various treatment methods;
(d) Flexural modulus of silane-treated PCB flour reinforced LLDPE composites with various PCB flour contents for
various water cross-linking times. This figure is available in colour online at www.apjChemEng.com.
been treated with interface modifiers exhibited greater
flexural strength than the untreated composites. Adding
PCB flour to the LLDPE matrix increases the initial
flexural modulus of the composites, but the composites
that have been treated with POE-g-MA compatibilizer
have a lower flexural modulus than untreated composites, because the POE is a rubber, which reduces the
flexural modulus of the composites. Longer water crosslinking time improves the flexural strength (from 21.9
to 24.8 MPa, or by 13.2%, during 4 h of water crosslinking treatment) and the flexural modulus (from 0.922
to 1.122 GPa, corresponding to an increase of 21.7%
after 4 h of water cross-linking treatment).
Impact properties
Figure 4(a) and (b) shows the notched impact strength
of PCB flour reinforced LLDPE composites. The results
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
of impact property testing are similar to those of tensile elongation testing. Composites with high PCB flour
content have low impact strength. PCB flour is a stiff
organic filler (compared to LLDPE), so adding PCB
flour reduces the impact strength of the composite.
Treatment with interface modifiers improved the impact
strength of the composite because the debonding behavior of the PCB flour/LLDPE matrix interface and the
rubber toughened matrix could lead to absorption of
more impact energy in modified composites than in
unmodified ones. Increasing the water cross-linking
time had an insignificant effect on the impact strength
of PCB flour reinforced LLDPE composite. The crosslinking reaction can limit the shear deformation behavior of the polymer matrix and slightly reduce the impact
strength of the PCB flour reinforced LLDPE composite. However, the cross-linking reaction also strengthens
the interface between PCB flour and the LLDPE matrix,
promoting the transfer of impact energy from the matrix
to the reinforcement, increasing the impact strength.
Asia-Pac. J. Chem. Eng. 2009; 4: 169–177
DOI: 10.1002/apj
173
C.-F. KUAN ET AL.
Asia-Pacific Journal of Chemical Engineering
200
Without Silane Treatment
With Silane Treatment
With Silane & Compatibilizer
180
160
140
120
100
80
60
40
140
Notched Izod Impact Strength (J/m)
Notched Izod Impact Strength (J/m)
174
130
120
40 %
50 %
60 %
110
100
90
80
70
60
50
40
45
50
55
60
PCB Flour Content (wt%)
(a)
0.0
(b)
0.5
1.0 1.5 2.0 2.5 3.0 3.5
Water-Crosslinking Time (hr)
4.0
4.5
(a) Comparison of the Izod impact strength of PCB flour reinforced LLDPE composites with various PCB
flour contents and various treatment methods; (b) Izod impact strength of silane-treated PCB flour reinforced LLDPE
composites with various PCB flour contents for various water cross-linking times. This figure is available in colour online at
www.apjChemEng.com.
Figure 4.
(a)
(b)
PCB Flour
PCB Flour
(c)
(d)
PCB Flour
Pulled Out
Figure 5. SEM microphotographs of fractured surface of PCB flour/LLDPE composites:
(a) modified PCB flour/LLDPE composites (200×); (b) modified PCB flour/LLDPE composites
(500×); (c) unmodified PCB flour/LLDPE composites (200×); (d) unmodified PCB
flour/LLDPE composites (500×).
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Asia-Pac. J. Chem. Eng. 2009; 4: 169–177
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
RECYCLED PCB FLOUR REINFORCED LLDPE COMPOSITES
96
Without Silane Treatment
With Silane Treatment
With Silane & Compatibilizer
80
Heat Deflection Temperature (°C)
Heat Deflection Temperature (°C)
85
75
70
65
60
40 wt%
50 wt%
60 wt%
94
92
90
88
86
84
82
80
78
76
74
55
72
0
(a)
10
20
30
40
50
0
60
PCB Flour Content ( wt% )
(b)
1
2
3
4
Water-Crosslinking Time (hr)
Figure 6. (a) Comparison of the heat deflection temperatures of PCB flour reinforced LLDPE composites with various PCB
flour contents and various treatment methods; (b) Heat deflection temperatures of silane-treated PCB flour reinforced
LLDPE composites with various PCB flour contents for various water cross-linking times. This figure is available in colour
online at www.apjChemEng.com.
These two factors compete with each other and accordingly, the water cross-linking reaction negligibly affects
impact strengths of the composites.
Fractured surface morphology
Figure 5(a–d) presents the morphology of the fracture
surface of the water cross-linked composite. They
reveal that some LLDPE resins remain attached to
the surface of PCB flour. Figure 5(b) shows that the
filler was pulled out and broken during the fracture
of the composite, but some strong adhesion bonding
still existed between the polymer matrix and the PCB
flour. This finding suggests good adhesion between the
matrix and the PCB flour. Therefore, the interfacial
strength is improved. A comparison with the fracture
surface of untreated PCB flour composite, as displayed
in Fig. 5(c) and (d), reveals many voids on the fractured
surface of the composite, pulling out of the filler, and
easy breakage during the fracture of the composite,
indicating a lack of bonding between PCB flour and
the LLDPE matrix.
Heat deflection temperature (HDT)
The HDT of PCB flour/LLDPE composites are plotted
in Figure 6(a) and (b). The figures demonstrate that the
HDT of the composite increases with increasing PCB
flour content. As the PCB flour content approaches 60
wt%, the HDT of the unmodified composite increases
from 55.8 to 79.7 ◦ C. Composites that have been treated
with silane exhibit higher HDTs, for example, the HDT
of 60 wt% treated PCB flour/LLDPE composite is
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
83 ◦ C (increase by 48.7%). Figure 6(b) indicates that
a composite that has undergone water cross-linking for
a longer time has a higher HDT, since the chemical
bonding between the filler and the polyethylene matrix
is better. The HDT of the silane-treated 60 wt% PCB
flour composite after 4 h of water cross-linking reaction
is 95.6 ◦ C, which is 15.2% higher than that, 83 ◦ C, of a
similar composite which had not undergone water crosslinking.
Thermal degradation properties
Figure 7(a) shows the TGA curves of 40, 50, and 60
wt% PCB flour reinforced LLDPE composites. The
thermal degradation of composites proceeds in three
steps. The first is the thermal degradation of PCB cellulose paper flour. The second is the thermal degradation
of LLDPE. The third is the thermal degradation of phenolic resin. Figure 7(b) shows that increasing the PCB
flour content increases the thermal degradation temperature of the composite in each thermal degradation
step. However, the thermal degradation temperatures at
which 40, 50, and 60 wt% PCB flour composites exhibit
10 wt% weight loss, are 331.6, 334.7, and 338.8 ◦ C,
respectively.
Figure 7(c) reveals that the onset temperatures of
thermal degradation increase with the water crosslinking time. In the second step of thermal degradation,
the ‘10% LLDPE weight loss’ temperatures of the 50
wt% PCB flour/LLDPE composites with 0 h and 4 h
of water cross-linking reaction are 420.0 and 440.3 ◦ C,
respectively. The results indicate that the cross-linking
reaction can increase the thermal degradation temperature of the composite.
Asia-Pac. J. Chem. Eng. 2009; 4: 169–177
DOI: 10.1002/apj
175
C.-F. KUAN ET AL.
Asia-Pacific Journal of Chemical Engineering
-35
40wt% (A)
50wt% (B)
60wt% (C)
(C)
80
(B)
(A)
60
40 wt% (A)
50 wt% (B)
60 wt% (C)
-30
Derivative Weight %
100
Weight Retention (%)
40
20
-25
-20
(A) 348.6 °C
(A) 541.1 °C
-15
(B) 547.0 °C
(C) 343.2 °C
-10
(B) 345.6 °C
(C) 590.2 °C
-5
0
0
0
100
(a)
200
300
400
500
600
700
800
0
100
200
(b)
Temperature (°C)
80
(A)
700
800
(B)
420.0 °C
(C)
40
(D)
20
0
PW55S
200
(c)
600
440.3 °C
Td10
60
300 400 500
Temperature (°C )
4 hr (A)
2 hr (B)
1 hr (C)
0 hr (D)
100
Weight Retention (%)
176
300
400
500
600
700
Temperature (°C)
Figure 7. (a) Comparison of the TGA curves of PCB flour reinforced LLDPE composites with various PCB flour contents;
(b) Comparison of the DTG curves of PCB flour reinforced LLDPE composites with various PCB flour contents; (c) TGA curves
of silane-treated PCB flour reinforced LLDPE composites with 50 wt% PCB flour contents for various water cross-linking
times. This figure is available in colour online at www.apjChemEng.com.
CONCLUSIONS
This work demonstrated that recycled PCB flour can be
used as a reinforcing filler material in a linear lowdensity polyethylene. A silane coupling agent and a
compatibilizer improve the compatibility between PCB
flour and LLDPE resin. Water cross-linking is an effective method for improving the physical properties of a
composite.
Tensile strength, flexural strength, and flexural modulus increase with increasing PCB flour content and
water cross-linking time. However, tensile elongation
and notched impact strength decline. The morphology
(SEM) indicates that the composites treated with silane
modifiers and water cross-linking process have much
stronger bonding between the filler and the matrix.
The HDT increases with the PCB flour content and
the water cross-linking time. The thermal degradation temperature increases with the water cross-linking
time.
 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Acknowledgements
The authors greatly appreciate the financial support for
this research by National Science Council of Taiwan
under the contract number NSC 95-2622-E-269-004CC3
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DOI: 10.1002/apj
177
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