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Melt compounding of thermoplastic polymers with carbon nanotubes
Petra Pötschke, Sven Pegel, Andreas Janke Leibniz Institute of Polymer Research Dresden Hohe Str. 6, 01069 Dresden, GermanyIngo Alig, Sergej M. DudkinDeutsches Kunststoff- Institut Schlossgartenstr. 6, 64289 Darmstadt, Germany
Workshop Dresden January 2005
Outline
1. Introduction
2. Composites of multiwalled carbon nanotubes (MWNT) with polycarbonate (PC)produced by masterbatch dilution technique
• Electrical resistivity• Dispersion and alignment• Influence of processing parameters on electrical resistivity
3. Composites of MWNT and SWNT with PC produced by direct incorporation• Percolation of different commercial MWNT in PC• Percolation of SWNT in PC• Stress-strain behaviour
4. Summary and Thanks
Workshop Dresden January 2005
Benefits of carbon nanotubes (CNT) to polymers
• Electrical conductivity
• Improvement of mechanical properties, especially strength
• Enhancement of thermal stability
• Enhancement of thermal conductivity
• Improvement of fire retardancy
• Enhancement of oxidation stability
Effects at low CNT contents because of the very high aspect ratio
How to introduce nanotubes into polymers
MWNT are produced as agglomerates SWNT are produced as bundles
• Suspensions of nanotubes in polymer solutions, preparation as thin films
• In-situ polymerization in presence of nanotubes
• Melt mixing of nanotubes with polymers
Problem: Deagglomeration and dispersion
Melt mixing of CNT with thermoplastic polymers
Starting from a masterbatch
Highly concentrated batch of polymer with 15-20 wt% CNTCommercially avalaible, p.e. Hyperion Catalysis Intern. Cambridge, USA
Direct incorporation
From solid premixtures of polymer powders/granules with CNT
Safety issues have to be considered
Wetting of the CNT by polymer•Surface characteristics and interfacial tension polymer-CNT•Melt viscosity of the polymer
Distribution Dispersion
Pure polymer
masterbatch
Pure polymer
CNT
Tasks
Pure polymer
masterbatch
nanocomposite
Preparation of the PC-MWNT composites
• masterbatch (Hyperion Catalysis International, Inc, Cambridge, USA) diluted with PC Iupilon E2000 (PC1), PC Lexan 121 (PC2) or PC as used for the masterbatch (PC3)
• Haake co-rotating, intermeshing twin screw extruder with one kilogramm mixtures• DACA Micro Compounder, conical twin screw extruder (4.5 cm3 capacity)• Brabender PL-19 single screw extruder
Masterbatch technology: polycarbonate (PC) + PC based masterbatch (15 wt% MWNT)
Characterization of the masterbatch (PC + 15 wt% MWNT)
SEM of fracture surfaces, no sputtering100 nmAFM of cut surface
Dispersion in PC-MWNT composites
1 wt% MWNT 2 wt% MWNT 5 wt% MWNT
Transmission electron microscopy
Extrusion direction
Thin section (200 nm, defocusing contrast)
• all samples are well dispersed, • and do not show agglomerates• however, percolation is detectable
• no indication of MWNT alignmentPötschke, Bhattacharyya, JankeEur. Polym. J. 40 (2004)1, 137-148
Alignment in PC-MWNT composites
Transmission electron microscopy
PC + 2wt% MWNT (cut along strand or fiber direction):
Extruded strand melt spun fiber (draw speed 800 m/min)
fiber axis
Comparison: different sets with PC masterbatches
0 1 2 3 4 5 6 710-1
102
105
108
1011
1014
1017 Masterbatch dilution performed at Hyperion: PC Hyperion
Dilution using DACA Micro Compounder:Masterbatch dilution using:
PC E 2000 (powder) PC Hyperion (granules) PC Hyperion (powder) PC Lexan 121 (granules)
Dilution using Brabender Single-screw extruder: PC Lexan 121 (granules)
Vol
ume
resi
stiv
ity (O
hm c
m)
Content of MWNT (wt%)
- full symbols measured with 8009A Resistivity Test Fixture, compression molded plates d= 60 mm, thickness 0.35mm- open symbols measured with four-point-method on small strips 10x3x0.35mm (cut from the sheets)
Detection of percolation and influence of processing conditions investigated by dielectric spectroscopy
prepared at 260°C, 150 rpm, 5 min variation of mixing conditions
100
101
102
10-5 10-3 10-1 101 103 105 107
100
101
102
Frequency, Hz
σ'
S/c
m
10-2
100
102
104
106
108
10-2
100
102
104
106
108
ε''
10-5 10-3 10-1 101 103 105 10710-18
10-14
10-10
10-6
10-2
10-18
10-14
10-10
10-6
10-2
2.03.04.0, 5.0
1.5
1.0
0,50
ε'
100
101
102
10-5 10-3 10-1 101 103 105 107
100
101
102
Frequency, Hz
σ' S
/cm
10-2
100
102
104
106
108
10-2
100
102
104
106
108
ε''
10-5 10-3 10-1 101 103 105 10710-18
10-14
10-10
10-6
10-2
10-18
10-14
10-10
10-6
10-2 NT% rpm min1,5 50 151,5 150 51,5 150 15
1,0 150 151,0 50 151,0 150 5
ε'
real part ε‘, imagionary part ε‘‘, and AC conductivity σ‘ for composites prepared from PC 2 and masterbatch using DACA Micro Compounder (Pötschke, Dudkin, Alig: Polymer,44(2003) 5023)
Direct incorporation of commercial MWNT into PC
MWNT2 = MWNT very thin straight and coiled, purity >60% (crude), diameter 5…(10)...15 nmMWNT3 = MWNT very thin straight and coiled, purity >95% (purified), diameter 5…(10)...15 nmNanocyl S.A. (Namur, Belgium), produced by CVDMWNT4 = TsNA-MWCnt1, purity >80%, diameter <10 nm Tsinghua-Nafine Nano-Powder Commercialization Engineering Center (TNNPCEC) Beijing, China
0 1 2 3 4 5 6100
103
106
109
1012
1015
1018 MWNT2 (Nanocyl, very thin crude) MWNT3 (Nanocyl,very thin purified) MWNT4 (TsNaMWCnt1, C-nano, China)
Vol
ume
resi
stiv
ity (O
hm c
m)
Content of MWNT in PC (wt%)
• PC = PC Iupilon E 2000 (6800 Pa-s at 260°C)
• Mixing using DACA-Microcompounder at 280°C, 50 rpm, 15 min
full symbols measured with 8009A Resistivity Test Fixture on 60 mm sheets, open symbols measured with four-point-method on small strips 10x3x0.35mm
Pötschke et al. Fullerenes, Nanotubes, and Carbon Nanostructures (2005), in press
• full symbols :8009A Resistivity Test Fixture on 60 mm sheets (thickness 0.35 mm) combined with Keithley 6517A• open symbols: four-point-method on small strips 10x3x0.35mm combined with Keithley DMM 2000
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16100
103
106
109
1012
1015
1018
MWNT Hyperion (masterbatch dilution)
MWNT3 (Nanocyl,very thin purified) MWNT4 (TsNaMWCnt1, C-nano, China) DWNT, Nanocyl purified CB Vulcan XC-72 (Cabot) CB Ketjenblack 300J (Akzo-Nobel)
Vol
ume
resi
stiv
ity (O
hm c
m)
Content of carbon filler in PC (wt%)
Comparison of direct incorporation of CNT, masterbatch dilution, and CB addition
MWNT2 (Nanocyl, very thin crude)
Direct incorporation of SWNT1 into PC
• SWNT produced at MPI Stuttgart (AG Dr. Roth)• unpurified arc-discharge material, dSWNT 1.0-1.3 nm, bundled• PC = PC Iupilon E 2000 (6800 Pa-s at 260°C)• Mixing using DACA-Microcompounder at 280°C, 50 rpm, 15 min
SEM of a buckypaper
0 500 1000 1500 2000 2500 3000
0
2000
4000
6000
8000
Radial breathing mode (RBM)
D-band
G-band
inte
nsity
(arb
. uni
ts)
Raman shift (cm-1)
Direct incorporation of SWNT1 into PC
0 1 2 3 4 5 6 7 810 3
10 4
10 5
10 6
10 7
10 8
10 9
10 1010 11
10 12
10 13
10 14
10 15
10 16
10 17
10 18
10 19
Vol
ume
resi
stiv
ity (O
hm c
m)
C on ten t S W N T (w t% )
SEM fractured sample 4wt% SWNT1
1 0 -3 1 0 -1 1 0 1 1 0 3 1 0 5 1 0 7
1 0 -1 7
1 0 -1 5
1 0 -1 3
1 0 -1 1
1 0 -9
1 0 -7
1 0 -5
1 0 -3
7 .5543
120
[S/c
m]
σ'
F re q u e n c y [H z ]
1 0 -2
1 0 0
1 0 2
1 0 4
1 0 6
1 0 8
1 0 1 0
ε''
1 0 0
1 0 1
1 0 2
ε'
DC
AC
Direct incorporation of SWNT1 into PC
0 1 2 3 4 5 6 7 8400
600
800
1000
40% increase
You
ng m
odul
us (M
Pa)
content of SWNT (wt%)
0 1 2 3 4 5 6 7 840
45
50
55
60
65
elon
gatio
n at
bre
ak (%
)
σ yield σ break
stre
ss (M
Pa)
content of SWNT (wt%)
0
20
40
60
80
100
ε break
0 50 1000
10
20
30
40
50
60
PC PC + 1% SWNT PC + 2% SWNT PC + 3% SWNT PC + 4% SWNT PC + 5% SWNT PC + 7.5% SWNT
Stre
ss (M
Pa)
Strain (%)
Pötschke et al. AIP Conference Proceedings 723 (2004) 478
• SWNT2= commercial SWNT from CNI Houston (TX, USA) delivered as buckypearls
• produced using high pressure decomposition of carbon monoxide supported by a Fe catalyst (HiPCO )
According to CNI:• metallic impurity level 5% • of the carbon, more than 95% SWNT• mean diameter is about 1 nm, lengths
between 0.3 and 1 µm, organized in ropes
Ropes of SWNTs, 10 – 80 nm wideDiameter of the SWNTs ~ 1 nmCatalyst particles - iron or iron oxide (EDS)TEM by Dr. M. C. Bunescu , TU WismarPhilips CM200, equipped with EDAX system
Direct incorporation of SWNT2 into PC
3000 2500 2000 1500 1000 5000
20000
40000
60000
80000
RBMD
G
D*
SWNT CNI
inte
nsity
(cou
nts)
Raman shift (cm-1)
Direct incorporation of SWNT2 into PC
• PC = PC Iupilon E 2000 (6800 Pa-s at 260°C), processing at 280°C, 50 rpm, 5 min
• SWNT2 as delivered (buckypearls)• SWNT2 predispersed in acetone under ultrasonification for 3 min, solvent removal, premixture of small pieces of the mat and PC added to the running compounder
Pötschke et al. Fullerenes, Nanotubes, and Carbon Nanostructures (2005), in press
Percolationbetween 0.30 and 0.35 wt% SWNT !
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6100
103
106
109
1012
1015
1018 SWNT2-PC powder premixtures SWNT2 pretreatment in acetone
Volu
me
resi
stiv
ity (O
hm c
m)
Content of SWNT (wt%)
Summary and Thanks
Melt mixing is a powerful method to disperse CNT into polymers
Masterbatch dilution technique (based on a PC masterbatch)• percolation in the range of 1.0 wt% MWNT • suitable processing conditions can shift percolation to lower values (0.5wt%)• effects of mixing equipment and PC viscosity on percolation are small
Direct incorporation method• percolation strongly depends on the kind of CNT, production method (resulting in different sizes, purity and defect levels), and the purifying/modification steps
• for commercial MWNT percolation occurs between 1.0 and 3.0 wt% and is lower atlower MWNT diameters and higher purity
• HipCO-SWNT (CNI) percolation between 0.30 and 0.35 wt% • stress-strain behavior of the composites: modulus and stress areenhanced, elongation at break reduced especially above percolation concentration
Thanks to:• Hyperion Catalysis International, Inc (Cambridge, USA) for supplying PC and masterbatch • German Federation of Industrial Cooperative Research Associations "Otto von Guericke" (AIF) forfinancial support of parts of this work within the project 122ZBG
• Nanofunpoly – Network of Excellence
Thanks to
IPF:• technicians : Monike Henze, Helfried Kunath (mixing)• Post-docs: A.R. Bhattacharyya , M. Abdel-Goad (rheology)• scientists: S. Pegel (phd, mixing, SEM), L. Häußler (DSC, TGA)
Cooperations:• A. Leonhardt (IFW Dresden, MWNT material, SEM of composites)• S. Roth, B. Hornbostel (MPI Stuttgart, SWNT material)• O. Decroly (Nanocyl S.A. Belgium, MWNT materials)• M. C. Bunescu , TU Wismar (TEM)
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