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

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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

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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

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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

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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

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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

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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)

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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 jeremy.klug@ticona.com

THANK YOU!

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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.