imerys-graphite-and-carbon.com

TIMCAL Graphite

TIMCAL Graphite

TIMREX®

TIMREX® C-THERMTM

SPECIALTY CARBONS FOR CARBON BRUSHES

EngineeringMaterials

TIMCAL CokeTIMREX®

2

Imerys Graphite & Carbon

WHAT IS OUR MISSION?To promote our economic, social and cultural advance-ment with enthusiasm, efficiency and dynamism by of-fering value, reliability and quality to ensure the lasting success of our customers.

WHAT IS OUR VISION?To be the worldwide leader and to be recognized as the reference for innovative capability in the field of carbon powder-based solutions.

Imerys Graphite & Carbon has a strong tradition and history in carbon manufacturing. Its first manufacturing operation was founded in 1908. Today, Imerys Graphite & Carbon facilities produce and market a large variety of synthetic and natural graphite powders, conductive carbon blacks and water-based dispersions of consistent high quality. Adhering to a philosophy of Total Quality Management and continuous process improve-ment, all Imerys Graphite & Carbon manufacturing plants comply with ISO 9001:2008. Imerys Graphite & Carbon is committed to produce highly specialized graphite and carbon materials for today’s and tomorrow’s customers needs.Imerys Graphite & Carbon belongs to Imerys, the world leader in mineral-based spe-cialties for industry.

WHO ARE WE?

HQ Bodio, SwitzerlandGraphitization and processing of synthetic graphite, manufacturing of water-based dispersions, processing of natural graphite and coke, and manufacturing and processing of silicon carbide

Changzhou, ChinaManufacturing of descaling agents and processing of natural graphite

Fuji, JapanManufacturing of water-based dispersions

Willebroek, BelgiumManufacturing and processing of conductive carbon black

Lac-des-Îles, CanadaMining, purification and sieving of natural graphite flakes

For the updated list of commercial offices and distributors please visit www.imerys-graphite-and-carbon.com

Terrebonne, CanadaExfoliation of natural graphite, processing of natural and synthetic graphite

With headquarters located in Switzerland, Imerys Graphite & Carbon has an inter-national presence with production facilities and commercial offices located in key markets around the globe. The Group’s industrial and commercial activities are man-aged by an experienced multinational team of more than 430 employees from many countries on three continents.

WHERE ARE WE LOCATED?

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Our value proposition

We at Imerys Graphite & Carbon deliver tailor made solutions for Carbon brushes market with superior consistency of key products’ parameters: purity, crystallinity, particles size distribution, oversize control.

We at Imerys Graphite & Carbon address with our portfolio and with our R&D efforts the key requirements of Carbon brushes industry:

APPLICATIONREQUIREMENTS

RELATED ISSUE CARBON ADDITIVES TECHNICAL REQUIREMENTSINVOLVED

BENEFITSFROM IMERYSGRAPHITE PORTFOLIO

Electrical resistivity Different resistivity depending on application

Various crystallinity levels and Particles Size Distribution (PSD).

Large variety of solutions, in terms of crystallinity and PSD.

Long life of electric motor

Wear resistance (electrical and mechanical)

High Purity, specific crystallinity and PSD for a tailored resistivity and friction coefficient (μ).

Consistent, high purity. Large variety of solutions, in terms of crystallinity and PSD. Thermal conductivity additive C-THERMTM.

Commutation film formation.

Special additive for transfer film’s thickness control.

Good adhesion between resin and graphite.

Engineered particles’ surface, optimized PSD.

Low carbon brush cost Low resin consumption

Optimized PSD. Large variety of solutions, in terms of PSD.

Good commutation, low noise, low sparking

Transfer film behavior,Vibration damping

Various crystallinity levels and PSD (depending on application).

Large variety of solutions, in terms of crystallinity and PSD.

Inspired by F.P. Bowden, D. Tabor (1964), “The friction and lubrication of solids”, Oxford University Press, UK.

High electrical resistivitylow/no compressibility

Nocrystallinity

Highcrystallinity

Low electrical resistivityhigh compressibility

Naturalgraphite

Coke

Secondarysynthetic graphiteor scrap graphite

Primarysynthetic graphiteT

KSKC

SFG

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Overview of Imerys Graphite & Carbon solutions

CARBON BRUSHES TYPE PROPERTIES

Graphite powders %C min. Resin bonded

Copper sintered

Electrical resistivity

Compressibility

Primary synthetic graphite T 99.9% High Low

KS 99.9% Medium high Medium

KC 99.9% Medium low Medium high

SFG 99.9% Low High

Natural graphite flakes BE 99.5% Low High

Flakes 94.0-96.0% Low High

Special additives Application benefits

Petroleum coke 99.5-99.7% Stabilization of friction coefficient

C-THERM™ 97.5-99.7% High thermal conductivity for lower wear

HRG High resistivity graphite 99.9% Very high el. resistivity, low oil absorption

ENSACO carbon black 99.9% Reduction of el. resistivity, mechanical resistance

Especially recommended Recommended

Medium-high resistivity primary synthetic graphite

High resistivityprimary synthetic graphite

0 20 40 60 80 100 120 140 160

T15

T44

T15-75

T150

T75

(µm)

0 20 40 60 80 100 120 140 160

KS6

KS15

KS25

KS5-25

KS5-75 TT

KS75

KS150

KS44

KS5-44

(µm)

5

0 200 400 600 800 1000 1200 1400 1600

PC40 OC

FC800

FC250-1500

FC250

(µm)

Calcinatedpetroleum coke

Natural flakes94 to 96%C

Natural flakes>99.5%C

Low resistivityprimary synthetic graphite

Medium-low resistivity primary synthetic graphite

0 20 40 60 80 100

KC44

KC75

KC5-44

(µm)

0 20 40 60 80 100 120 140 160

BE44

BE90

BE75

(µm)

(µm)0 50 100 150 200 250 300 350

PP25

50X80

50X100

M80

M150

PP44

M100

0 20 40 60 80 100 120 140 160

SFG6

SFG15

SFG44

SFG5-75

SFG150

SFG75

(µm)

6

Tests methods

Model Carbon brushes have been prepared in R&D lab following the standard procedure:– Mixing: graphite powder is dry mixed with phenolic resin powder (typically 80% wt. graphite – 20% wt. resin or 70% wt. graphite – 30% wt. resin)– Compaction: the mixed powders are pressed in a rectangular mould (either 20 x 30 mm2, 50x12 mm2 or 5x35 mm2) at different pressures (from 1 t/cm2 to 5 t/cm2)– Curing: the pressed samples are cured in an oven according to the following

thermal treatment: 25 -> 80 °C (120 minutes), 80 -> 135 °C (660 minutes), 135 -> 180 °C (270 minutes), 120 minutes at 180 °C, cooling

The dimensions of the model carbon brushes are measured after the thermal treat-ment with a micrometer, the weight is measured with a precision balance, and the density is calculated (mass/volume).

The transverse rupture strength is measured by three point method: the sample is placed on two supporting pins a set distance apart and a third loading pin is lowered from above at a constant rate until sample failure.

PRESSED DENSITY

SAMPLES PREPARATION

BENDING STRENGTH

L

T

Pressed Density: Mass / W x L x T

Pressure

Load

Carbon brush

W

7

The electrical resistivity is measured by the four-point method both in the in-plane (XY) and through-plane (Z) direction. The four-point method applied for these measurements greatly reduces the possibility of errors due to poor contacts.

The thermal conductivity is measured with TCT416 instrument by Netzsch.

ELECTRICAL RESISTIVITY

Current carrying electrodes

Measuring electrodes

Carbon brush

IDC

Digital Ohmmeter

Digital Ohmmeter

Current carryingelectrodes

Measuringelectrodes(gold wires)

IDC Carbonbrush

Interlayer(graphite foil)

XY (in-plane)

Z (through-plane)

THERMAL CONDUCTIVITY

T = 60C

T = 25C

T2

T1

Car

bon

brus

h

8

The measurement of elastic springback gives an indication of the the resilience of com-pacted graphite powder. A defined amount of dry powder is poured into a die. After inserting the punch and sealing the die, air is evacuated from the powder. Pressure is applied (p=0.477 t/cm2) and the powder sample thickness is measured. Thickness is measured again after pressure has been released.

SPRING-BACKMEASURINGMETHOD

Pressure meter

Punch

Meteringelement

Seal

Die

Compact

Vacuum line

Pressure

Springback

SB =H (0) - H (p)

H (0)x 100%

The oil absorption test is a special centrifugation method showing high reproducibility, developed by Imerys Graphite & Carbon. A special centrifuge tube is filled with 0.5 g ofTIMREX® graphite powder and then covered with paraffin oil. After centrifuging, the tube is weighed and the oil absorption of 100 g of powder is calculated (based upon the weight increase of the 0.5 g sample).

OIL ABSORPTION MEASURING METHOD

Acceleration

CentrifugationTube

Oil

SampleFilterSieve

9

Data: pressed density

Pres

sed

dens

ity (g

/cm

3 )

Pressure (t/cm2)

4 6 820

1.7

1.9

1.6

1.5

1.4

2.2

2.1

2.0

1.8

BE44

SFG44

KS44

T44

Pres

sed

dens

ity (g

/cm

3 )

Pressure (t/cm2)

4 620

1.6

1.8

1.5

1.4

1.3

1.9

1.7

BE150

SFG150

KS150

T150

Pres

sed

dens

ity (g

/cm

3 )

100 150500

1.7

1.9

1.6

1.5

1.4

1.3

2.1

2.0

1.8

Particles size d90 (microns)

BE

SFG

KS

KC

T

Pres

sed

dens

ity (g

/cm

3 )

Particles size d90 (microns)

100 150500

1.3

1.5

1.2

1.8

1.7

1.6

1.4

BE

SFG

KS

KC

T

Carbon brush(20% wt. resin)

Pure graphite (2.5 t/cm2

compacting pressure)

Carbon brush(30% wt. resin, 2 t/cm2

compacting pressure)

Pure graphite

Pressed density increases with increasing applied pressure. Natural graphite (BE) has higher pressed density compared to primary synthetic graphite. Pressed density of primary synthetic grades can be ranked according to crystallinity level (T<KS<KC<SFG).For synthetic graphite of type T and KS, the pressed density significantly decreases with increasing particle size.

Pressed density vs. graphite type

Pressed density vs. particles size distribution

10

Data: springback and bending strength

Carbon brush(30% wt. resin, 2 t/cm2 compacting pressure)

Bend

ing

stre

ngth

(MPa

)

100 150500

30

20

60

50

40

BE

SFG

KS

T

Particles size d90 (microns)

Springbackof pure graphite

Sprin

gbac

k (%

)

Particles size d90 (microns)

100 150500

5.0

15.0

0

30.0

25.0

20.0

10.0

BE

SFG

KS

KC

T

Springback and compact density of graphite powders are physically connected parame-ters, which give information about the compressibility of powders and dimensional stabil-ity of compacts in any pressing direction. Springback is influenced mainly by compacting pressure, particle size distribution and crystalline structure of graphite. Typically, high crystalline structure results in low springback. Compacts produced from powders having a low springback can be easily formed and pressed with greater accuracy and density.

Bending strength of carbon brushes typically decreases with increasing particles size distribution (d90). This trend is more evident for high crystallinity grades (SFG, natural graphite).

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Data: electrical resistivity

Elec

trica

l res

istiv

ity X

Y (m

Ohm

.cm

)

0

5

15

30

25

20

10

Particles size d90 (microns)

BE

SFG

KS

KC

T

80 160120400

Elec

trica

l res

istiv

ity Z

(mOh

m.c

m)

80 1601204000

40

120

200

160

80

Particles size d90 (microns)

BE

SFG

KS

KC

T

Carbon brush(30% wt. resin, 2 t/cm2

compacting pressure)

It has to be taken into consideration that the compressibility of each graphite grade affects the electrical resistivity because of micro-cracks and residual porosity of the carbon brush.

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Data: electrical resistivity-anisotropy

The electrical resistivity of carbon brushes is highly anisotropic, due to the orientation of the graphite particles during compression. Electrical resistivity anisotropy (through-plane / in-plane electrical resistivity) can range from a ratio of circa 6 for KS primary synthetic graphite up to circa 14 for natural graphite (BE).

Elec

trica

l res

istiv

ity X

Y (m

Ohm

.cm

)

Pressed density (g/cm3)

0

10

20

15

5

BE150

SFG150

T150

KS150

1.70 1.901.501.30

Elec

trica

l res

istiv

ity a

niso

tropy

Pressed density (g/cm3)

0

8

6

4

2

16

12

14

10

1.70 1.901.501.30

BE150

SFG150

T150

KS150

Elec

trica

l res

istiv

ity Z

(mOh

m.c

m)

Pressed density (g/cm3)

0

80

120

100

60

40

1.70 1.901.501.30

BE150

SFG150

T150

KS150

Carbon brush(20% wt. resin, 2-5 t/cm2

compacting pressure)

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Benefits from optimized particles size distribution

We at IMERYS Graphite & Carbon have developed a long time ago optimized particle size distributions to match a few key requirements of carbon brush producers:– Lower cost of carbon brushes can be obtained thanks to resin consumption

reduced by 30 to 50%– Higher wear resistance can be obtained thanks to reduced electrical wear

(significantly less sparking) and mechanical wear– Better commutation properties– Lower brush density, with higher electrical resistivity and improved mechanical

properties– More elasticity for better noise-vibration performance

Oil a

bsor

ptio

n (g

oil

/ 100

g g

raph

ite)

0

40

20

80

120

100

60

PSD

Optimized PSD

KS25

KS5–

25

KS44

KS5–

44

KS75

KS5–

75 T

T

T75

T15–

75

SFG7

5

SFG–

75

KC44

KC5–

44

Elec

trica

l res

istiv

ity (m

Ohm

.cm

)

Pressed density (g/cm3)

1

10

1000

100

rho XY KS5–75 TT

rho XY KS75

rho Z KS75

rho Z KS5–75 TT

1.6 1.71.51.4

Bend

ing

stre

ngth

(N/m

m2 )

Pressed density (g/cm3)

25

20

35

30

KS5–75 TT

KS75

1.6 1.71.51.415

Carbon brush(20% wt. resin, 2, 3, 5 t/cm2 compacting pressure)

Oil absorptionof pure graphite

The absorption behaviour is determined by particle size distribution, bulk density, crystalline structure, BET, surface porosity, particle shape and surface tension between graphite and binder.

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Special grades / Additives

HRG GRAPHITE

TYPICAL VALUES KS44 KS75 HRG250

Malvern d10 [μm] 5 5 5

Malvern d50 [μm] 18 23 19

Malvern d90 [μm] 46 56 52

Oil Absorption [%] 94 83 65

Scott density [g/cm3] 0.19 0.24 0.31

Carbon brush(30% wt. resin0.5–2 t/cm2

compacting pressure)

Elec

trica

l res

istiv

ity (m

Ohm

.cm

)

Pressed density (g/cm3)

0

500

400

300

200

100

rho XY HRG250

rho XY KS75

rho Z KS75

rho Z HRG250

1.4 1.51.31.2

HRG shows:– Much higher resistivity with similar pressed density compared to T / KS – Lower oil absorption by about 30% compared to KS – Higher Scott density by about 40% compared to KS – Mechanical properties similar or better than T / KS– Improved wear properties thanks to optimized shape and surface structure of

powder grains– Improved commutation but lower efficiency (more power consumption P=R*I2)

High resistivity graphite (HRG) was developed to combine high resistivity (typical of sec-ondary synthetic graphite, obtained by scrapping of electrodes) with the high mechanical performance given by primary synthetic graphite.

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C-THERMTM

ENSACO CARBON BLACK / COKE

POWDER SOFT GRANULES

>99.7 %C C-THERMTM002 C-THERMTM001

>97.5 %C C-THERMTM012 C-THERMTM011

Elec

trica

l res

istiv

ity (m

Ohm

.cm

)

Ther

mal

con

duct

ivity

(W/m

.K)

0

2.52

1.51

3.5

4.5 140

120

100

80

60

40

20

0

4

3

In-plane electricalresistivity (4 t/cm2)In-plane thermalconductivity (2.5 t/cm2)

0.5

% KS75 / C-THERMTM

80 / 0 75 / 5 70 / 10 60 / 20 40 / 40 0 / 80

C-THERMTM can be used as minor additive to improve the thermal conductivity (better heatdissipation, resulting in lower wear of the carbon brush). It can be also used to decrease the electrical resistivity of the carbon brush. It is available both as powder and soft granules with two different purity levels.

We at IMERYS Graphite & Carbon can provide special Carbon based additives for specific needs in carbon brushes formulation:– stabilization of friction layer and friction coefficient (fine Coke powders, with oversize

control)– tailoring of electrical resistivity values (ENSACO® electrically conductive carbon black)

ENSACO® 250G is a conductive carbon black that can boost both in-plane andthrough-plane electrical conductivity of polymer-carbon composites.

Carbon brush(20% wt. resin)

Carbon brush(TIMREX® KS150 + ENSACO®

250G and 20% wt. resin;2 t/cm2 compacting pressure)

ENSACO® 250G content (wt. %)

Elec

trica

l res

istiv

ity in

-pla

ne (m

Ohm

.cm

)

Elec

trica

l res

istiv

ity th

roug

h-pl

ane

(mOh

m.c

m)

50 7.5

7

6

8

9

10

0

15

5

25

30

20

10

35 In-plane XY

Through-plane Z

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EUROPE

Imerys Graphite & Carbon Switzerland Ltd. Group Head Office • Strada Industriale 12 • 6743 Bodio • SwitzerlandTel: +41 91 873 20 10 • Fax: +41 91 873 20 19 • graphiteandcarbon.ch@imerys.com

Imerys Graphite & Carbon Belgium SABrownfieldlaan 19 • 2830 Willebroek • BelgiumTel: +32 3 886 71 81 • Fax: +32 3 886 47 73 • graphiteandcarbon.be@imerys.com

Imerys Graphite & Carbon Germany GmbHBerliner Allee 47 • 40212 Düsseldorf • GermanyTel: +49 211 130 66 70 • Fax: +49 211 130 667 13 • graphiteandcarbon.de@imerys.com

France Representative Office c/o Imerys154-156 rue de l’Université • 75007 Paris • FranceTel: +33 1 495 565 90/91 • Fax: +33 1 495 565 95 • graphiteandcarbon.fr@imerys.com

UK Representative OfficeTel: +44 1 270 212 263 • Fax: +44 1 270 212 263 • graphiteandcarbon.uk@imerys.com

ASIA-PACIFIC

Imerys Graphite & Carbon Japan K.K. Tokyo Club Building 13F • 3-2-6 Kasumigaseki • Chiyoda-ku • Tokyo 100-0013 • JapanTel: +81 3 551 032 50 • Fax: +81 3 551 032 51 • graphiteandcarbon.jp@imerys.com

Imerys Graphite & Carbon (Changzhou) Co. Ltd. 188# Taishan Road • Hi-Tech Zone • Changzhou 213022 • ChinaTel: +86 519 851 008 01 • Fax: +86 519 851 013 22 • graphiteandcarbon.cn@imerys.com

Shanghai Branch Office c/o Imerys 1438 Hong Qiao Road • Chang Ning District 6F • Gubei International Fortune Centre II Shanghai 201103 • ChinaTel: + 86 21 2223 0136 • Fax: + 86 21 2223 0199 • graphiteandcarbon.cn@imerys.com

Singapore Representative Office c/o Imerys Asia Pacific80 Robinson Road #19-02 • 068898 SingaporeTel: +65 67 996 060 • Fax: +65 67 996 061 • graphiteandcarbon.sg@imerys.com

AMERICAS

Imerys Graphite & Carbon USA Inc. 29299 Clemens Road 1-L • Westlake (OH) 44145 • USATel: +1 440 871 75 04 • Fax: +1 440 871 60 26 • graphiteandcarbon.us@imerys.com

Imerys Graphite & Carbon Canada Inc. 990 rue Fernand-Poitras • Terrebonne (QC) J6Y 1V1 • Canada Tel: +1 450 622 91 91 • Fax: +1 450 622 86 92 • graphiteandcarbon.ca@imerys.com

Imerys Graphite & Carbon is a trademark of the Imerys Group © 2

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