Engineering
Materials
SPECIALTY CARBONS FOR
CARBON BRUSHES
TIMREX
®
TIMCAL Graphite
TIMREX
®
TIMCAL Coke
TIMREX C-THERM
®
TIMCAL Graphite
imerys-graphite-and-carbon.com
TM
Imerys Graphite & Carbon
WHO ARE WE?
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 improvement, 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 specialties for industry.
WHERE ARE
WE LOCATED?
With headquarters located in Switzerland, Imerys Graphite & Carbon has an international presence with production facilities and commercial offices located in key
markets around the globe. The Group’s industrial and commercial activities are managed by an experienced multinational team of more than 430 employees from many
countries on three continents.
For the updated list of commercial offices and distributors please visit
www.imerys-graphite-and-carbon.com
Lac-des-Îles, Canada
Mining, purification and sieving of
natural graphite flakes
HQ Bodio, Switzerland
Graphitization and processing of
synthetic graphite, manufacturing of
water-based dispersions, processing
of natural graphite and coke, and
manufacturing and processing of
silicon carbide
Changzhou, China
Manufacturing of descaling agents
and processing of natural graphite
Terrebonne, Canada
Exfoliation of natural graphite,
processing of natural and synthetic
graphite
Willebroek, Belgium
Manufacturing and processing of
conductive carbon black
Fuji, Japan
Manufacturing of water-based
dispersions
WHAT IS OUR MISSION?
To promote our economic, social and cultural advancement with enthusiasm, efficiency and dynamism by offering 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.
2
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:
APPLICATION
REQUIREMENTS
RELATED ISSUE
CARBON ADDITIVES
TECHNICAL
REQUIREMENTS
INVOLVED
BENEFITS
FROM IMERYS
GRAPHITE
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.
Coke
No
crystallinity
High electrical
resistivity
low/no
compressibility
Secondary
synthetic graphite
or scrap graphite
T
KS
Primary
synthetic graphite
KC
SFG
Natural
graphite
Low electrical
resistivity
high
compressibility
High
crystallinity
Inspired by F.P. Bowden, D. Tabor (1964), “The friction and lubrication of solids”, Oxford University Press, UK.
3
Overview of Imerys Graphite & Carbon solutions
CARBON BRUSHES TYPE
PROPERTIES
%C min.
Resin
bonded
Electrical
resistivity
T
99.9%

KS
99.9%

KC
99.9%
SFG
Graphite powders
Primary synthetic graphite
Natural graphite flakes
Copper
sintered
Compressibility
High
Low

Medium high
Medium


Medium low
Medium high
99.9%


Low
High
BE
99.5%


Low
High
Flakes
94.0-96.0%

Low
High
Special additives
Application benefits
Petroleum coke
99.5-99.7%

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

Stabilization of friction coefficient
 Recommended
High resistivity
primary synthetic graphite
T150
T15-75
T75
T44
T15
Medium-high resistivity
primary synthetic graphite
0
20
40
60
80
100
120
140
160 (µm)
0
20
40
60
80
100
120
140
160 (µm)
KS150
KS5-75 TT
KS75
KS5-44
KS44
KS5-25
KS25
KS15
KS6
4
Medium-low resistivity
primary synthetic graphite
KC75
KC5-44
KC44
0
Low resistivity
primary synthetic graphite
20
40
60
100 (µm)
80
SFG150
SFG5-75
SFG75
SFG44
SFG15
SFG6
Natural flakes
>99.5%C
0
20
40
60
80
100
120
140
160 (µm)
0
20
40
60
80
100
120
140
160 (µm)
BE90
BE75
BE44
Natural flakes
94 to 96%C
50X80
50X100
M80
M100
M150
PP44
PP25
Calcinated
petroleum coke
0
50
0
200
100
150
200
250
300
350 (µm)
FC250-1500
FC800
FC250
PC40 OC
400
600
800
1000
1200
1400 1600 (µm)
5
Tests methods
SAMPLES
PREPARATION
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
PRESSED DENSITY
The dimensions of the model carbon brushes are measured after the thermal treatment with a micrometer, the weight is measured with a precision balance, and the
density is calculated (mass/volume).
Pressure
W
T
L
Pressed Density: Mass / W x L x T
BENDING STRENGTH
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.
Load
Carbon brush
6
ELECTRICAL
RESISTIVITY
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.
XY (in-plane)
Measuring electrodes
Carbon brush
IDC
Current carrying electrodes
Digital Ohmmeter
Z (through-plane)
Measuring
electrodes
(gold wires)
IDC
Carbon
brush
Current carrying
electrodes
Interlayer
(graphite foil)
Digital Ohmmeter
The thermal conductivity is measured with TCT416 instrument by Netzsch.
T = 25C
T1
Carbon brush
THERMAL
CONDUCTIVITY
T2
T = 60C
7
SPRING-BACK
MEASURING
METHOD
The measurement of elastic springback gives an indication of the the resilience of compacted 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.
Pressure meter
Metering
element
Punch
Pressure
Seal
Spring
back
Die
Compact
Vacuum line
OIL ABSORPTION
MEASURING METHOD
SB =
H (0) - H (p)
H (0)
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 of
TIMREX® 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).
Acceleration
Tube
Oil
Sample
Filter
Sieve
8
x 100%
Centrifugation
Data: pressed density
Pure graphite
Pressed density (g/cm3)
Pressed density vs. graphite type
2.2
BE44
2.1
SFG44
2.0
KS44
1.9
T44
1.8
1.7
1.6
1.5
1.4
0
4
2
6
8
Carbon brush
(20% wt. resin)
Pressed density (g/cm3)
Pressure (t/cm2)
1.9
BE150
SFG150
1.8
KS150
1.7
T150
1.6
1.5
1.4
1.3
0
2
4
6
Pressure (t/cm2)
Pure graphite
(2.5 t/cm2
compacting pressure)
Pressed density (g/cm3)
Pressed density vs. particles size distribution
2.1
BE
2.0
SFG
1.9
KC
1.8
KS
1.7
T
1.6
1.5
1.4
1.3
0
50
100
150
Carbon brush
(30% wt. resin, 2 t/cm2
compacting pressure)
Pressed density (g/cm3)
Particles size d90 (microns)
1.8
BE
SFG
1.7
KC
1.6
KS
1.5
T
1.4
1.3
1.2
0
50
100
150
Particles size d90 (microns)
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.
9
Springback
of pure graphite
Springback (%)
Data: springback and bending strength
30.0
BE
SFG
25.0
KC
20.0
KS
15.0
T
10.0
5.0
0
0
50
100
150
Particles size d90 (microns)
Carbon brush
(30% wt. resin, 2 t/cm2
compacting pressure)
Bending strength (MPa)
Springback and compact density of graphite powders are physically connected parameters, which give information about the compressibility of powders and dimensional stability 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.
60
BE
SFG
KS
50
T
40
30
20
0
50
100
150
Particles size d90 (microns)
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).
10
30
BE
SFG
25
KC
20
KS
15
T
10
5
0
0
40
80
120
160
Particles size d90 (microns)
Electrical resistivity Z (mOhm.cm)
Carbon brush
(30% wt. resin, 2 t/cm2
compacting pressure)
Electrical resistivity XY (mOhm.cm)
Data: electrical resistivity
200
BE
SFG
160
KC
KS
120
T
80
40
0
0
40
80
120
160
Particles size d90 (microns)
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.
11
Carbon brush
(20% wt. resin, 2-5 t/cm2
compacting pressure)
Electrical resistivity XY (mOhm.cm)
Data: electrical resistivity-anisotropy
20
BE150
SFG150
15
KS150
T150
10
5
0
1.30
1.50
1.70
1.90
Electrical resistivity Z (mOhm.cm)
Pressed density (g/cm3)
120
BE150
SFG150
100
KS150
T150
80
60
40
0
1.30
1.50
1.70
1.90
Electrical resistivity anisotropy
Pressed density (g/cm3)
16
BE150
14
SFG150
12
KS150
10
T150
8
6
4
2
0
1.30
1.50
1.70
1.90
Pressed density (g/cm3)
The electrical resistivity of carbon brushes is highly anisotropic, due to the orientation
of the graphite particles during compression. Electrical resistivity anisotropy (throughplane / 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).
12
Benefits from optimized particles size distribution
120
PSD
Optimized PSD
100
80
60
40
20
KC44
KC5–44
SFG75
SFG–75
T75
T15–75
KS75
KS5–75 TT
KS44
KS5–44
KS25
0
KS5–25
Oil absorption
of pure graphite
Oil absorption (g oil / 100 g graphite)
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
1000
rho XY KS5–75 TT
rho XY KS75
rho Z KS5–75 TT
100
rho Z KS75
10
1
1.4
1.5
1.6
1.7
Pressed density (g/cm3)
Bending strength (N/mm2)
Carbon brush
(20% wt. resin, 2, 3, 5 t/cm2
compacting pressure)
Electrical resistivity (mOhm.cm)
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.
35
KS5–75 TT
KS75
30
25
20
15
1.4
1.5
1.6
1.7
Pressed density (g/cm3)
13
Special grades / Additives
HRG GRAPHITE
High resistivity graphite (HRG) was developed to combine high resistivity (typical of secondary synthetic graphite, obtained by scrapping of electrodes) with the high mechanical
performance given by primary synthetic graphite.
TYPICAL VALUES
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
Electrical resistivity (mOhm.cm)
Carbon brush
(30% wt. resin
0.5–2 t/cm2
compacting pressure)
KS44
500
rho XY HRG250
rho XY KS75
400
rho Z HRG250
rho Z KS75
300
200
100
0
1.2
1.3
1.4
1.5
Pressed density (g/cm3)
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)
14
C-THERMTM can be used as minor additive to improve the thermal conductivity (better heat
dissipation, 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.
Carbon brush
(20% wt. resin)
Electrical resistivity (mOhm.cm)
POWDER
SOFT GRANULES
>99.7 %C
C-THERMTM002
C-THERMTM001
>97.5 %C
C-THERMTM012
C-THERMTM011
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
140
120
100
80
60
40
Thermal conductivity (W/m.K)
C-THERMTM
In-plane electrical
resistivity (4 t/cm2)
In-plane thermal
conductivity (2.5 t/cm2)
20
0
80 / 0
75 / 5
70 / 10
60 / 20
40 / 40
0 / 80
% KS75 / C-THERMTM
ENSACO CARBON
BLACK / COKE
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)
10
35
30
9
25
8
20
7
15
10
6
5
0
5
0
7.5
Electrical resistivity through-plane (mOhm.cm)
Carbon brush
(TIMREX® KS150 + ENSACO®
250G and 20% wt. resin;
2 t/cm2 compacting pressure)
Electrical resistivity in-plane (mOhm.cm)
ENSACO® 250G is a conductive carbon black that can boost both in-plane and
through-plane electrical conductivity of polymer-carbon composites.
In-plane XY
Through-plane Z
ENSACO® 250G content (wt. %)
15
EUROPE
Imerys Graphite & Carbon Switzerland Ltd.
Group Head Office • Strada Industriale 12 • 6743 Bodio • Switzerland
Tel: +41 91 873 20 10 • Fax: +41 91 873 20 19 • graphiteandcarbon.ch@imerys.com
Imerys Graphite & Carbon Belgium SA
Brownfieldlaan 19 • 2830 Willebroek • Belgium
Tel: +32 3 886 71 81 • Fax: +32 3 886 47 73 • graphiteandcarbon.be@imerys.com
Imerys Graphite & Carbon Germany GmbH
Berliner Allee 47 • 40212 Düsseldorf • Germany
Tel: +49 211 130 66 70 • Fax: +49 211 130 667 13 • graphiteandcarbon.de@imerys.com
UK Representative Office
Tel: +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 • Japan
Tel: +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 • China
Tel: +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 • China
Tel: + 86 21 2223 0136 • Fax: + 86 21 2223 0199 • graphiteandcarbon.cn@imerys.com
Singapore Representative Office c/o Imerys Asia Pacific
80 Robinson Road #19-02 • 068898 Singapore
Tel: +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 • USA
Tel: +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
16
Imerys Graphite & Carbon is a trademark of the Imerys Group
© 2014 Imerys Graphite & Carbon CH-Bodio. No part of this publication may be reproduced in any form without the prior written authorisation.
France Representative Office c/o Imerys
154-156 rue de l’Université • 75007 Paris • France
Tel: +33 1 495 565 90/91 • Fax: +33 1 495 565 95 • graphiteandcarbon.fr@imerys.com