Flame Retardant - Hyperion Catalysis International

Flame Retardant - Hyperion Catalysis International

52nd IWCS/FOCUS
____________________________________________________
Carbon Multiwall Nanotubes
A Possible Additive for
Conductive or Flame Retardant Use in
Wire and Cable
____________________________________________________
Patrick Collins
Hyperion Catalysis International, Inc.
Structure of a FIBRILTM Nanotube
A unique carbon structure
• Graphitic wall structure
• Multilayer
• Hollow
Images are Copyright © 2000
™ FIBRIL is a trademark of Hyperion Catalysis International, Inc.
Structure of FIBRIL Nanotubes
FIBRIL nanotubes form excellent networks
•
•
•
•
Curvilinear rather than perfectly straight
Approx. length (L): 10,000 nm
Approx. diameter (D): 10 nm
Aspect Ratio: L/D = 1000
Hollow
Image is Copyright © 2000
Comparison with Carbon Black
Nanotubes are significantly different
• Nanotubes have a
higher aspect ratio
• Nanotubes are more
inert and more
chemically pure
Images are Copyright © 2000
One long nanotube winds it’s way through the image.
Comparison with Carbon Fiber
Nanotubes are significantly different
• Nanotubes are 1000
times smaller and have a
higher aspect ratio
• Nanotubes have no
sizing or coupling agents
to compromise purity
Images are Copyright © 2000
Effect of Aspect Ratio on Loading
High aspect ratio = low loading for conductivity
Loading
Theoretical Percolation Threshold
40%
35%
30%
25%
20%
15%
10%
5%
0%
Spheres (L/D=1)
Carbon Black
(L/D~10)
Carbon Fiber
(L/D ~100)
FIBRIL nanotubes
(L/D~1000)
Nanotubes as Conductive Additive
2% in Polycarbonate Gives ESD Conductivity
Polycarbonate Percolation Curve
Volume Resistivity
1.00E+07
Volume Resistivity (ohm-cm)
1.00E+06
1.00E+05
1.00E+04
1.00E+03
1.00E+02
1.00E+01
1.00E+00
0
1
2
3
4
% Fibril Loading
5
6
7
Conductive Additive Comparison
Study done by CRIF in Belgium in PC/ABS
• Carbon Black
• Carbon Fiber
• Carbon Nanotubes
CENTRE DE RECHERCHES SCIENTIFIQUES ET TECHNIQUES DE L'INDUSTRIE DES FABRICATIONS METALLIQUES
CRIF
Commercial PC/ABS Compounds
Formulated To Similar Level Of Surface Resistivity
Additive
None
Nanotubes
Carbon Black
Carbon Fiber
Volume
Surface
Loading Resistivity Resistivity
wt%
(ohm-cm)
(ohms)
16
7.3
16.7
13.7
10
1
3
10 - 10
3
10
3
10
n.a.
4
6
10 - 10
6
10
6
10
Additive Effect on Ductility
Nanotubes Give Least Reduction In Ductility
Additive
None
Nanotubes
Carbon Black
Carbon Fiber
Elongation Un-Notched
Loading
at Break
Izod
wt%
(%)
(ft lbs)
7.3
16.7
13.7
100
10+
3
1-3
NB
30
10
4
Additive Effect on Part Surface
Nanotubes Give Smoothest Part Surface
©
Additive Effect on Resin Viscosity
Nanotubes Have Least Effect on Viscosity
Apparent Viscosity at 280C
Viscosity (Pa s)
1.E+05
1.E+04
PC/ABS
PC/ABS + 7.3% NF
1.E+03
PC/ABS+ 13.7% CF
PC/ABS+ 16.7% CB
1.E+02
1.E+01
1.E+00
1.E+01
1.E+02
Frequency (Rad/s)
1.E+03
Nanotubes in Plastics
Summary of Resin Physical Properties Benefits
• Low loading
– Preserves more of base resin properties such as
toughness
– Minimal effect on resin viscosity
• Small size
– Excellent part surface quality
– Highly isotropic distribution within part
• Lower risk of particle contamination
– Less sloughing
– Less abrasion
• Lower risk of vapor contamination
– Less outgassing
FIBRIL Nanotubes in Plastics
Multiple conductive applications commercialized
Automotive
• Fuel Lines
• Painted Body Panels
and Hardware
Electronics
• Semiconductor
Processing Equipment
• Hard Disc Drive
Manufacturing
• Clean Room Equipment
• ESD Shipping Trays
Most Plastics Are Combustible
Multiple hazards from burning plastics
• Heat release
• Dense smoke
• Toxic gasses
flame retarded
TV set
non-flame retarded
TV set
Several Types of Flame Retardants
• Heat Absorbers: decompose to liberate cooling
water
• Flame Quenchers: interrupt chemical reactions
in the flame
• Synergists: enhance performance of flame
quenchers
• Char Formers: provide an insulating layer
against heat and choke off fuel source
– Char Reinforcers: preserve structural
integrity of char
Measuring FR Performance
Cone calorimeters are widely used
Heat release
rate is single
most important
variable in a
fire and can be
viewed as the
driving force of
the fire.
Structure of FIBRIL Nanotubes
FIBRIL nanotubes form excellent networks
•
•
•
•
Curvilinear rather than perfectly straight
Approx. length (L): 10,000 nm
Approx. diameter (D): 10 nm
Aspect Ratio: L/D = 1000
Hollow
Image is Copyright © 2000
Nanotubes / Nanoclays in EVA
• Nanotubes lower peak heat release rate (PHRR)
better then nanoclays
• Nanotubes + nanoclays synergistically reduce PHRR
CMWNT
wt. %
Nanoclay
wt. %
Peak Heat Release Rate
kW/m2
0
0
580
0
2.4
530
0
4.8
470
2.4
0
520
4.8
0
405
2.4
2.4
370
Beyer G., Fire and Materials, 2002; 26: 291-293
Nanotubes / Nanoclays in EVA
4.8% organoclay
600
4.8% pure CMWNT
RHR [kW/m²]
500
2.4% pure CMWNT
400
+
2.4% organoclay
300
200
100
0
0
100
200
300
400
Time [sec]
Beyer G., Fire and Materials, 2002; 26: 291-293
500
600
Nanotubes as an FR in EVA
Mechanism may be char reinforcement, especially
in mixed system
4.8% nanotube
4.8% nanoclay
2.4% nanoclay
plus
2.4% nanotube
Beyer G., Fire and Materials, 2002; 26: 291-293
Nanotubes as an FR in PP
Peak heat release rate
greatly reduced
Several possible reasons
suggested, but exact
mechanism not yet
confirmed
– Iron in catalyst used to
grow nanotubes may
be acting as the FR
– Char reinforcement by
nanotubes discounted
in this resin
T. Kashiwagi, Macromol. Rapid Commun. 2002; 23, 761-765
CMWNT FR Benefit Overview
• Non-Halogenated
– Environmental improvement
– Regulatory driven, especially in EU
• Low Loadings
– Preserves base resin properties
– Minimizes viscosity increase
– Maintains flexibility, toughness
– Preserves formulation versatility
– FR possible with or without electrical conductivity
FIBRIL Nanotubes as an FR in
Plastics
EVA masterbatch let down into EVA and PE
• Peak Heat Release (PHR) rate reduced by
FIBRIL nanotubes in both EVA and PE
• Nanoclays, and blends of nanoclays with
FIBRIL nanotubes, work in polar EVA but not in
non-polar PE
Beyer G., Presentation at 2003 BCC Conference on Flame Retardants
Hyperion EVA Masterbatch in EVA
Heat Release for EVA compounds at 35 kW / m2 flux
EVA
600
EVA + 5% organoclay
550
500
RHR [kW/m²]
450
EVA + 2.5% organoclay
+ 2.5% FIBRIL CMWNT
400
350
300
250
EVA + 5% FIBRIL CMWNT
200
150
100
50
0
0
50
100
150
200
250
300
350
400
450
500
550
Time [sec]
Beyer G., Presentation at 2003 BCC Conference on Flame Retardants
600
Hyperion EVA Masterbatch in PE
Heat Release for PE compounds at 35 kW / m2 flux
PE + 5% organoclay
550
500
PE
450
400
PE + 2.5% organoclay
+ 2.5% FIBRIL CMWNT
RHR [kW/m²]
350
300
250
200
PE + 5% FIBRIL CMWNT
150
100
50
0
0
100
200
300
400
500
600
Time [sec]
Beyer G., Presentation at 2003 BCC Conference on Flame Retardants