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)