1
Electrically Conductive Acetals for Fuel Environments
SPE ACCESeptember 11-13, 2007
Presented by:Jeremy Klug, POM Product DevelopmentTicona Engineering Polymers
2
Overview
Charge mitigation - impetusTest methods and fuelsPolymer charge mitigation – additivesPolyoxymethylene (POM) material performance– Mechanical, electrical, fuel exposure
Future direction – conductive POMAcknowledgements
3
“Driving” Force ....
SAE J1645 – Fuel Systems & Components – Electrostatic Charge Mitigation
Liquid, flowing fuel in autos4.1.6 Material Recommendation
– Virgin material representative of intended production process• ρV ≤ 1x104 Ω·m AND• Surface resistance not exceed empirically derived value
consistent with recommendations of 4.1.5
4.1.5 Component Recommendations– In its system application, Resistance ≤ 1x106 Ω OR– Static dissipation time td ≤ 0.5 sec (when V=0.1Vi)
Material Component Assembly
4
Challenges in Electrical Testing
All electrical testing is not created equal!Sample size and preparation– Geometry & molding– Conditioning– Contact resistance reduction
• conductive paint• other means
Test instrumentation– Electrode shape and size– Contact force
Measurement parameters– Test voltages (non-Ohmic responses)– Voltage sequencing– Electrification/charging time
From Ticona ESD WebinarWith Stan Weitz
President, ElectroTech Systems
5
Fuel Exposure of Dissipative Materials
Alcohol, non-alcohol, aggressive, diesel (including bio) fuelsFrom SAE J1645– The effect of prolonged immersion in fuels described in 5.4.1
should be evaluated by physical testing. Where it is found that such immersion adversely affects the material......
– A.3.1.3.2 Many plastic and rubber materials can be made conductive by blending them with conductive additives. However, increasing conductivity may alter other properties of the material, such as:
• Mechanical properties (e.g., impact resistance, flexibility, etc.)• Chemical resistance (e.g., fuel, sour gas, exposure to road
chemicals) • Permeation resistance
The proper balance of properties is critical
6
Polymer Systems that Dissipate
Inherently conducting polymers or blendsConductivity imparted to POM by additives– Carbon powder– Carbon fiber– Carbon/graphite nano-material– Metals
Minor Anisotropy
Unchanged
Slightly higher
Stainless Steel Fiber
Minor Anisotropy
Unchanged
Potentially Higher
Nano-filler
IsotropicAnisotropicShrinkage
LowLowestElongation
SimilarMuch HigherStiffness &
strength
Carbon Powder
Carbon Fiber
Property vs. unfilled POM
7
Percolation & Dispersion
Ideally, the level of conductive additive needed to impart dissipative characteristics is...– Governed by the aspect ratio of the filler
In reality, dispersion is never perfect
Low
R
esis
tivity
Hig
h
Low Conductive Additive loading High
Minimum required additive loading
Insulative
Conductive
8
POM – Carbon Experimental
Hostaform® POM base material used for all formulationsStabilization consistent across like groupsProcessing common across like groupsFunctional levels of conductive fillers usedPerformance*:– Flow– Impact– Mechanical – Electrical resistance– After fuel exposure
Reference
DevelopmentPOM – Nanofiber
Celcon EF10POM – Carbon Fiber
DevelopmentPOM – Nanotube
Hostaform EC140XFPOM – Carbon PowderCelcon® CF802POM – Steel Fiber
Hostaform C13031XFPOM – Improved Flow
Hostaform C9021POM – Standard Flow
* in-house laboratory testing except for fuel-exposed tensile specimens
9
Carbon Comparisons
Taken from published datasheets
Representative Values
Bulk Density (kg/m3)
Characteristic Size* (nm)
Aspect Ratio
Surface Area (m2/g)
Resistivity (Ω·cm)
Relative Particles Per Given Mass
Conductive Carbon Powder 150 500 <10 1000
Carbon Fiber 500 10000 x 1000000 100 <5 1.50E-03 1
Nanofiber 15 100 x 10000+ 100+ 20 20 E+03
Nanotube 150 10 x 1000+ 100+ 200 1.00E-04 200 E+06
* Carbon black denotes aggregate size, others represent effective size after compounding
10
Flow Behavior
Melt Volume Rate at 190°C, 2.16 kgFunctional loadings of additives
8
12
4 4
6
4
0
2
4
6
8
10
12
14
POM -Standard
Flow
POM -Improved
Flow
POM-CarbonPowder
POM -Carbon
Fiber
POM -Nanofiber
POM -Nanotube
MVR
(cm
3/10
min
)
110
140
Results at elevatedload: 190°C, 15 kg
11
Impact Results
Notched Charpy (ISO 179) - room temperature
5
2.5
4
4.54.5
7.56.5
0
1
2
3
4
5
6
7
8
POM -Standard
Flow
POM -Improved
Flow
POM -SteelFiber
POM-CarbonPowder
POM -Carbon
Fiber
POM -Nanofiber
POM -Nanotube
23C
Not
ched
Cha
rpy
(kJ/
m2)
12
Tensile Modulus Values
Primarily governed by additive content, modulus, aspect ratio
2800
3100
2700
3900
2850 2900
2000
2500
3000
3500
4000
POM -Standard
Flow
POM -Improved
Flow
POM - SteelFiber
POM-CarbonPowder
POM -Carbon
Fiber
POM -Nanofiber
POM -Nanotube
Tens
ile M
odul
us (M
Pa)
8500
ISO-527-1
13
Elongation at Break Results
Response prone to more variability
30 30
20
16
10
2
17
0
5
10
15
20
25
30
35
POM -Standard
Flow
POM -Improved
Flow
POM - SteelFiber
POM-CarbonPowder
POM -Carbon
Fiber
POM -Nanofiber
POM -Nanotube
Elon
gatio
n at
Bre
ak (%
)
ISO-527-1
14
Mechanical Property Comparison
Tensile Strength (MPa)
Elongation @ Break (%)
MVR (g/10min)Notched Charpy (kJ/m2)
Tensile Modulus (MPa)
Hostaform EC140XF
Celcon EF10
POM-Nano-fiberPOM Nano-tube
Hostaform C9021
15
Electrical ResistanceVolume resistance
via:ISO tensile bars– Cut to 80 mm– Ag painted
ends– Tested at 10V– Reading after
10 seconds
Surface resistance via:ISO tensile bars– ETS Model
880– 10V
IM plaques 2 mm thick @ 3V
Surf
ace
Res
ista
nce
(Ohm
)
1E+04
1E+03
1E+02
1E+01
1E+06
1E+05
1.00E+03 1.00E+03
1.00E+02
5E+041E+04
20
55
25
38
0
10
20
30
40
50
POM - SteelFiber
POM-CarbonPowder
POM -Carbon Fiber
POM -Nanofiber
POM -Nanotube
Volu
me
Res
istiv
ity (O
hm c
m)
POM - SteelFiber
POM-CarbonPowder
POM -Carbon Fiber
POM -Nanofiber
POM -Nanotube
1E+02
1E+07
16
Peroxide Fuel Performance - I
POM - Carbon powder formulationFuel exposure– Ford PN180 w/copper test for 360 hours, 60°C– GM PN108 test for 336 hours, 40°C; two refresh rates
Tensile Stress at Yield49
404545
0
10
20
30
40
50
60
Control Ford PN180 withCopper
GM PN108 (72hrs.)
GM PN108 (168hrs.)
MPa
17
Peroxide Fuel Performance - I
POM - Carbon powder formulation No indications of resistivity increase
Volume Resistivity
99
58 5772
0
20
40
60
80
100
120
Control Ford PN180 withCopper
GM PN108 (72hrs.)
GM PN108 (168hrs.)
Ohm
-cm
18
Peroxide Fuel Performance – II
More Aggressive fuel exposure– Ford PN180 w/copper test for 360 hours, 65°C, one fuel refresh
Perc
ent
Prop
erty
Ret
enti
on
PropertyMaterial
Yield StressElongation at BreakPOM - NTPOM - NFPOM - CPPOM - NTPOM - NFPOM - CP
160
140
120
100
80
60
40
20
0
100
7570
17
147
20
44
Fuel Exposure GM PN180 360 hr 65CCP = Carbon Powder, NF = Nanofiber, NT = Nanotube
19
Degrading Peroxide Exposure
Extended time, elevated temperature or peroxide number can lead to degradation
DegradedUnaffected
Ticona POM -Steel fiber formulation(from a different study)
POM - Carbon powder
POM - Nanofiber POM - Nanotube
20
Future Direction - Conductive POM
“Nano” benefits and challenges– Lower functional loadings– Robust manufacturing– Strength enhancements– Understanding of resistivity & molding– Safety/regulatory & intellectual property
Dispersion improvements– Understand fundamentals & drive to better levels
Improved stability to aggressive fuels
21
Acknowledgements
Conference organizersAttendeesColleagues, including– Dwight Smith Ticona Application Dev. Eng.– Ralf Langhammer Ticona EU Market Development– John Stieha Ticona Product Specialist
– Jeremy Klug (859) 372-3272 [email protected]
THANK YOU!
22
NOTICE TO USERS:
Information is current as of August 3, 2007 and is subject to change without notice.
The information contained in this publication should not be construed as a promise or guarantee of specific properties of our products.
Any determination of the suitability of a particular material and part design for any use contemplated by the user is the sole responsibility of the user. We strongly recommend that users seek and adhere tothe manufacturer’s current instructions for handling each material they use.
Any existing intellectual property rights must be observed.
© 2007 Ticona. Except as otherwise noted, trademarks are owned by Ticona or its affiliates.
Top Related