Carbon Additives for Polymer Compounds

Polymers
Carbon Additives for
Polymer Compounds
Conductive Carbon Black
Graphite & Coke
www.timcal.com
1
Who are we?
TIMCAL Graphite & Carbon has a strong tradition and history in carbon manufacturing. Its
first manufacturing operation was founded in
1908.
Today, TIMCAL facilities produce and market a
large variety of synthetic and natural graphite
powders, conductive carbon blacks and waterbased dispersions of consistent high quality.
Adhering to a philosophy of Total Quality Man-
agement and continuous process improvement, all TIMCAL manufacturing plants comply
with ISO 9001-2008.
TIMCAL Graphite & Carbon is committed to
produce highly specialized graphite and carbon materials for today’s and tomorrow’s customers needs.
TIMCAL Graphite & Carbon is a member of IMERYS,
a world leader in adding value to minerals.
Where are we located?
With headquarters located in Switzerland, TIMCAL
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.
HQ Bodio, Switzerland
Graphitization & processing of synthetic
graphite, manufacturing
of water-based dispersions,
processing of natural
graphite & coke and
manufacturing & processing of silicon carbide
Willebroek, Belgium
Manufacturing & processing of conductive
carbon black
Lac-des-Îles, Canada
Mining, purification and
sieving of natural
graphite flakes
Terrebonne, Canada
Exfoliation of natural
graphite, processing of
natural and synthetic
graphite
Baotou, China
Purification, intercalation,
exfoliation, size reduction, shape modification
and sieving & classifying
of natural graphite
Changzhou, China
Manufacturing of
descaling agents and
processing of natural
graphite
Fuji, Japan
Manufacturing of
water-based dispersions
For the updated list of
commercial offices and
distributors please visit
www.timcal.com
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
Contents
ENSACO® Conductive Carbon Black
TIMREX® Graphite and Coke
Carbon additives for polymer compounds
The products
• Introduction to ENSACO® Conductive Carbon Black
p. 4
• Introduction to TIMREX® Graphite and Coke
p. 5
• ENSACO® Conductive Carbon Black for polymer compounds
p. 6
• TIMREX® Graphite and Coke for polymer compounds
p. 8
Typical applications for ENSACO® Conductive Carbon Black
• Electrically conductive plastics
p. 10
• Rubber
p. 14
• Power cables and accessories
p. 17
Typical applications for TIMREX® Graphite and Coke
• Self lubricating polymers
p. 18
• Filled PTFE
p. 20
• Thermally conductive polymers
p. 22
3
Introduction to ENSACO®
Conductive Carbon Black
Conductive carbon blacks are carbon blacks
with high to very high stucture (or void volume)
allowing the retention of a carbon network at
low to very low filler content. The void volume
can originate from the interstices between the
carbon black particles, due to their complex arrangement, and from the porosity.
TEM picture of ENSACO® 250 G
Carbon Black showing the high
level of aggregation.
By courtesy of University of
Louvain (Louvain-La-Neuve)
100 nm
the product
How ENSACO® Conductive Carbon
Blacks are produced
The Timcal carbon black process has been developed around 1980 and is commercially exploited since 1982. The plant uses most modern
technology. The process is based on partial oil
oxidation of carbochemical and petrochemical
origin. The major difference with other partial
combustion carbon black technologies lies in
the aerodynamic and thermodynamic conditions:
• low velocity;
• no quench;
• no additives.
This leads to a material with no or nearly no
sieve residue on the 325 mesh sieve and allows
the highest possible purity.
The granulation process has been developed to
achieve an homogeneously consistent product
maintaining an outstanding dispersibility. It is in
fact a free-flowing soft flake characterised by a
homogeneous and very low crushing strength
that guarantees the absence of bigger and
harder agglomerates.
The process enables the production of easily
dispersible low surface area conductive carbon
blacks as well as very high surface area conductive carbon blacks. The unique combination of
high structure and low surface area also contributes to give outstanding dispersibility and
smooth surface finish. The low surface area materials show a chain-like structure comparable
to acetylene black. The very high surface area
materials belong to the Extra Conductive (EC)
family. Although ENSACO® Carbon Blacks are
slightly more graphitic than furnace blacks, they
are quite close to the latter ones as far as reinforcement is concerned.
ENSACO® Carbon Blacks combine to a certain
extent both the properties of furnace and acetylene black, reaching the optimal compromise.
4
STM picture of the surface of
ENSACO® 250 G Carbon Black
5x5 nm.
By courtesy Prof. Donnet - Mulhouse
SEM picture of ENSACO® 250 G
Carbon Black illustrating the
high void volume.
By courtesy of University of
Louvain (Louvain-La-Neuve)
100 nm
Introduction to TIMREX®
Graphite and Coke
• low friction, chemical inertness and
absence of inherent abrasiveness;
• high thermal conductivity, thermal
stability and electrical conductivity;
• film forming ability on metal surfaces;
• relatively inoffensive nature of both
powders and products of combustion.
These properties are a consequence of the lamellar graphite structure and the anisotropic
nature of chemical bonding between carbon
atoms. In graphite, three sp2 hybrid orbitals
(each containing one electron) are formed
from the 2s and two of the 2p orbitals of each
carbon atom and participate in covalent bonding with three surrounding carbon atoms in the
graphite planes. The fourth electron is located
in the remaining 2p orbital, which projects
above and below the graphite plane, to form
part of a polyaromatic π-system.
Delocalisation of electrons in π-electron system is the reason of graphite’s high stability
and electrical conductivity. Interlamellar bonding was once thought to be weak and mainly
the result of Van der Waals forces, however, it
now appears that interlamellar bonding is reinforced by π-electron interactions. Graphite is
therefore not intrinsically a solid lubricant and
requires the presence of adsorbed vapours to
maintain low friction and wear.
the product
Graphite finds wide application thanks to its
favourable combination of properties such as:
How TIMREX® Graphite and Coke
powders are produced
TIMREX® Primary Synthetic Graphite
TIMREX® Primary Synthetic Graphite is produced in a unique highly controlled graphitization process which assures narrow specifications
and unequalled consistent quality thanks to:
monitoring of all production and processing
stages, strict final inspection, and clearly defined development processes.
TIMREX® Primary Synthetic Graphite shows
unique properties thanks to the combination of
a consistent purity, perfect crystalline structure
and well defined texture.
SEM picture of TIMREX® Graphite showing the perfect
crystalline structure.
TIMREX® Natural Flake Graphite
TIMREX® Natural Flake Graphite is produced
in a wide range of products distinguished by
particle size distribution, chemistry and carbon
content. Timcal mines the graphite from its own
source in Lac-des-Îles, Quebec, Canada. Further
processing can be done either in Lac-des-Îles or
in our processing plant in Terrebonne, Quebec,
Canada. All TIMREX® “Naturals” are thoroughly
controlled in our laboratories to ensure quality,
consistency and total customer satisfaction.
Lc
c
c/2
TIMREX® Coke
TIMREX® Petroleum Coke is calcined at appropriate temperature with low ash and sulphur
content, well defined texture and consistent
particle size distribution.
c/2 = Interlayer distance
Lc = Crystallite height
5
ENSACO® Conductive Carbon Black
for polymer compounds
Typical values
Property Test Method
UNIT
Form
BET Nitrogen Surface Area
ENSACO® 210 G
ENSACO® 250 G
ENSACO® 260 G
ENSACO® 350 G
Granules (*)
Granules
Granules (*)
Granules
Granules
m2/g
50
55
65
70
770
ml/100 g
165
155
190
190
320
ml/100 g
95
95
104
104
270
kg/m3
190
210
170
170
135
%
0.1
0.1
0.1
0.1
1 max
ppm
2
2
2
2
10
%
0.1
0.1
0.01
0.01
0.03
%
0.2 max
0.2 max
0.2 max
0.2 max
0.3 max
Sulphur Content
ASTM D1619
%
0.5 max
0.5 max
0.02
0.02
0.02
Toluene Extract
ASTM D4527
%
0.1 max
0.1 max
0.1 max
0.1 max
0.1 max
8–11
8–11
8–11
8–11
8–11
500 max (3)
10 max (3)
5 max (3)
20 max (4)
ASTM D3037
OAN
Absorption
ASTM D2414
(1)
COAN Crushed OAN
ASTM D2414
(1)
Pour Density
ASTM D1513
the product
ENSACO® 150 G
Moisture (as packed)
ASTM D1509
Sieve residue
325 mesh (45 μm)
ASTM D1514
Ash Content
ASTM D1506
Volatile Content
TIMCAL Method 02
(2)
pH
ASTM D1512
Volume Resistivity
TIMCAL Method 11
(3) (4)
Ohm.cm
2000 max
(1) Spring: 0.9 lbs/inch; 10 g of carbon black
(2)Weight loss during heating between 105 and 950°C
(3)25% carbon black in HDPE Finathene 47100
(4)15% carbon black in HDPE Finathene 47100
(*) ENSACO® 150 and ENSACO® 250 are also available in powder form.
6
(3)
ENSACO® Conductive Carbon Black
for polymer compounds
Property
ENSACO® 150 G
ENSACO® 210 G
ENSACO® 250 G
ENSACO® 260 G
ENSACO® 350 G
Form
Granules (*)
Granules
Granules (*)
Granules
Granules
BET Nitrogen Surface Area (m2/g)
50
55
65
70
770
OAN Oil Absorption (ml/100 g)
165
155
190
190
320
Conductivity
    
Dispersibility
    
Purity
    
Water absorption
very low
Surface smoothness
    
Electrical/Mechanical
properties balance
    
Resistance to shear
    
Comments to
application domains
MRG
(Mechanical
Rubber Goods)
very low
Easy strippable
insulation shields
very low
very low
high
All polymers


good

quite good 
difficult

excellent very good
(*) ENSACO® 150 and ENSACO® 250 are also available in powder form.
7
the product
Typical effects on polymer compounds
TIMREX® Graphite and Coke
for polymer compounds
Typical values
Particle size range d90 (µm)
Grade
Ash
(%)
Scott density
(g/cm3)
Surface area
Bet (m2/g)
Synthetic Graphite
KS Graphite
0.06
0.07
26.0
KS 15
0.05
0.07
20.0
KS 5-25
0.03
0.23
8.6
KS 44
0.06
0.19
9.0
KS 5-44
0.02
0.31
5.9
KS 150
0.06
0.42
3.0
SFG 6
0.07
0.07
17.0
SFG 44
0.07
0.19
5.0
SFG 150
0.03
0.29*
2.5
T 15
0.08
0.10
13.0
T 44
0.07
0.18
10.0
T 75
0.07
0.21
9.8
PP 10
<5
0.05
10.0
PP 44
<5
0.11
4.8
LSG 10
<1
0.08
9.3
LSG 44
<1
0.20
5.4
min. 80% <150 mesh (105 µm)
M150
<6
0.4*
1.9
min. 80% >150 mesh (105 µm)
80X150
<6
0.6*
0.9
PC 40-OC
0.15
0.47*
10.0
0
25
50
75
150
SFG Graphite
the product
KS 6
0
25
50
75
150
T Graphite
0
25
50
75
150
Natural Graphite
PP Flake
Graphite
0
25
50
75
150
LSG Flake
Graphite
0
25
50
75
150
cumulative size
Large flake
graphite
Coke
oversize control
PC Coke
min. 98% <45 µm (air jet sieving)
max. 0,1% >106 µm (air jet sieving)
Grade
Ash
(%)
Density
(g/cm3)
20°C
Particle size
distribution
d90 (µm)
Solid content
(%)
Water-based dispersion
LB Dispersion
LB 1300
Grade
0.10
Ash
(%)
1.17
Scott density
(g/cm3)
6.5
Form
27.5
d90
(µm)
Special Grade
C-THERM™
* bulk density
8
C-THERM™001
<0.3
0.15*
soft granules
C-THERM™011
<2.5
0.15*
soft granules
C-THERM™002
<0.3
0.04*
powder
81
C-THERM™012
<2.5
0.04*
powder
81
EnSACo® Conductive Carbon Black
TIMREX® Graphite
for polymer compounds
Conductivity
Targets
9
Typical applications for ENSACO® Conductive Carbon Black
Electrically
conductive plastics
The selection of a
conductive carbon black
Some typical final
plastics applications
ENSACO® Conductive Carbon Blacks find their
applications in an unlimited number of plastics.
The combination of the polymer type and grade
and the carbon black grade are determining the
overall electrical and mechanical performance.
The main parameter influencing the final conductivity of a finished part in a given polymer is
the type and level of carbon black used.
The higher the structure of the carbon black,
the lower the level of carbon black needed to
achieve the required conductivity. Nevertheless,
in a minor way, other parameters like the additives in presence, the compounding or processing conditions may also influence the final
conductivity of parts.
Low surface area conductive carbon blacks
show a particular advantage on dispersion and
processing.
Percolation curves – correlating the volume resistivity and the carbon black percentage – are
a useful comparative tool to predict the conductivity in place and to select the more appropriate system. These curves are valid for a given
formulation and sample preparation technique.
The selection of the conductive carbon black
will also influence:
• the compounding behaviour
(dispersibility, resistance to shear, mixing
cycle, melt flow index, extrusion throughput);
• the surface appearance of the finished material (number of surface defects);
• the mechanical properties
(polymer property retention, reinforcement);
• the overall price – performance ratio.
• handling of electronic components: carrier
boxes, carrier trays, carrier tapes, etc.;
• films: antistatic and conductive films,
packaging films, garbage bags, etc.;
• automotive industry: fuel injection systems,
anticorrosion systems, fuel tank inlet,
electrostatically paintable parts, etc.;
• transport: mobile phone parts, wheels,
containers, bins, pallets, etc.;
• computer: antistatic articles for computer &
accessories, CD player, etc.;
• health: medical applications, cleanroom
equipments, articles for antistatic
workplaces, etc.;
• antistatic flooring;
• heating element;
• sensors;
• PTC switches;
• UV protection and pigmentation.
The preparation
of a conductive compound
Suitable mixing equipments for the preparation
of black conductive compounds include internal mixers, twin screw extruders, single screw
kneader machines and LCM. The feeding of low
bulk density, soft flake-type carbon blacks into
extruders requires the use of twin screw feeders
and separate introduction on an already molten
polymer (split feeding technology).
10
In the following pages there are some of the results of experimental work carried out on ENSACO® Conductive Carbon Blacks in different
polymer compounds.
The data shown here are given as orientation
and are valid for the particular formulations and
sample preparation technique mentioned.
Results in other polymers, full studies and publications are available upon request.
TYpICAL AppLICATIonS FoR EnSACo® ConduCTIvE CARBon BLACk
EnSACo® ConduCTIvE CARBon BLACkS In HdpE
Influence of the carbon black type on the
resistivity
various carbon blacks in HdpE
The higher the structure of the carbon black,
the lower the percolation threshold.
Volume Resistivity [Ohm.cm]
109
Compounding: laboratory Brabender internal mixer.
Processing: compression moulding.
ENSACO® 250 G
ENSACO® 260 G
107
ENSACO® 350 G
105
103
10
0.1
0
10
20
30
40
50
Carbon Black %
Resistivity vs mixing time - 18% carbon black
800
Volume Resistivity [Ohm.cm]
At a concentration very near to the percolation
level, when overmixed, ENSACO® 260 G offers a
higher consistency in resistivity resulting from
its higher shear stability in extreme working
conditions.
ENSACO® 250 G
700
ENSACO® 260 G
600
500
400
300
200
100
0
4
5
6
7
8
9
10
Brabender Mixing Time [min]
Resistivity vs mixing time - 25% carbon black
7.0
Volume Resistivity [Ohm.cm]
At a concentration far above the percolation
level, both blacks are very stable in resistivity
when overmixed. ENSACO® 260 G shows a consistent lower resistivity.
ENSACO® 250 G
6.5
ENSACO® 260 G
6.0
5.5
5.0
4.5
4.0
3.5
3.0
4
5
6
7
8
9
10
Brabender Mixing Time [min]
11
Compounding: laboratory Brabender internal mixer.
Processing: compression moulding.
The higher the structure of the carbon black,
the lower the percolation threshold.
At equal structure, the carbon black of lower
surface area gets an advantage on resistivity
that may be coming from the easier dispersion
resulting in smoother compounding. The higher
the meltflow index of the starting polymer, the
lower the percolation threshold.
various carbon black in LdpE MFI 0.3 and 36 (g/10 min)
108
Volume Resistivity [Ohm.cm]
Influence of the carbon black type and of the
MFI of the starting polymer on the resistivity
E250 G LD 0.3
E250 G LD 36
106
104
N472
LD 0.3
N472
LD 36
P-type
LD 0.3
P-type
LD 36
102
100
0
5
10
15
20
25
30
35
Carbon Black Concentration [%]
EnSACo® ConduCTIvE CARBon BLACkS In pp
Compounding and processing: twin screw extruder Haake PTW16
and realization of tapes.
At same structure level, the carbon black with
the lowest surface area has the smallest impact
on fluidity reduction.
ppH MI54 (230 °C/5 kg) with various conductive carbon blacks
104
Volume Resistivity [Ohm.cm]
Influence of the carbon black type on the
resistivity. Relation between resistivity and
melt flow index
E250 G
high structure
low surface area
103
N472
high structure
high surface area
102
101
100
0
10
100
MFI [230 °C/5 kg] [g/10 min]
Influence of carbon black loading and
processing on the resistivity
Compounding: ZSK25 twin screw extruder.
Processing: injection moulding.
Injection moulding generates more shear than
compression moulding. The closest to the percolation, the more visible is that effect. A concentration safety margin can overcome this
phenomenon.
106
Volume Resistivity [Ohm.cm]
TYpICAL AppLICATIonS FoR EnSACo® ConduCTIvE CARBon BLACk
EnSACo® ConduCTIvE CARBon BLACkS In LdpE
13.50% E250 G
4.6E + 10
105
104
103
171
54
102
24
101
10
6
100
strands
12
15% E250 G
pellets + pressed
pellets +
plaques
injection moulding
TYpICAL AppLICATIonS FoR EnSACo® ConduCTIvE CARBon BLACk
EnSACo® ConduCTIvE CARBon BLACkS In pC
Influence of the carbon black type
on the resistivity
volume Resistivity (vR) in function of carbon black loading
Volume Resistivity [log (Ohm.cm)]
12
Compounding: ZSK57 twin screw extruder.
Processing: injection moulding.
ENSACO® 250 G
11
ENSACO® 350 G
10
9
8
7
6
5
4
3
2
1
5
10
15
20
25
Carbon Black concentration [%]
Influence of the carbon black type on
mechanical and rheological performances
Izod impact strength, notched, in function of vR
12
Compounding: ZSK57 twin screw extruder.
Processing: injection moulding.
ENSACO® 250 G
11
ENSACO® 350 G
Although the concentration for percolation is
double the level with ENSACO® 250 G, most
mechanical properties are still better.
Izod [kJ/m2]
10
9
8
7
6
5
4
1
2
3
4
5
6
7
8
9
10
11
12
Volume Resistivity [log (Ohm.cm)]
Tensile strength in function of vR
68
ENSACO® 250 G
67
Tensile Strength [MPa]
Tensile Strength for both carbon blacks is almost
at the same level.
ENSACO® 350 G
66
65
64
63
62
61
60
1
2
3
4
5
6
7
8
9
10
11
12
Volume Resistivity [log (Ohm.cm)]
13
Typical applications for ENSACO® Conductive Carbon Black
Rubber
Carbon black is one of the main ingredients
of any rubber compound. Conductive carbon
blacks are before all carbon blacks, to be mixed
and handled as any other reinforcing or semireinforcing carbon black. They are high structure
materials bulky by nature. Although the common carbon blacks are conductive by nature
and impart also conductivity to the compounds
when used in sufficiently high loading, conductive carbon blacks have the advantage to reach
conductivities at lower loading and are often
used to give the final boost to a compound already filled with other carbon blacks. As carbon
black structure is the parameter determining
the conductivity, structure being an additive
property, the combinations of conductive and
normal black can be predicted.
Specifications of rubber compounds being usually quite complex and conductivity being only
one of the numerous physical requirements, the
use of carbon black blends is very often the
only solution. In some specific cases, especially
in special polymers, it occurs that the conductive carbon black is used by its own in order to
maintain mechanical properties and processing
at a good level.
ENSACO® carbon blacks are, quite close to furnace blacks as far as the reinforcing activity is
concerned. Especially the low surface area carbon blacks, grades 150, 250 and 260, are, due to
their very easy dispersion, quite performing in
most rubber compounds. ENSACO® 350 is also
used in some compounds where small additions
are required.
14
A few conductive applications:
• belt cover compounds;
• flooring;
• conveyer belts;
• hoses for fuel, for conveying of powders, etc.;
• cylinder coating;
• shoe soles;
• seals.
ENSACO® 150 and 250 are also used in non conducting applications where the compounder
can take profit of the low surface area and high
structure of those blacks:
• low hysteresis with relatively high hardness;
• good thermal aging;
• very good tear strength;
• very good dispersion, very good mechanical performance at thin layer.
A few non-conductive applications:
• antivibration systems;
• textile coating;
• membranes;
• articles exposed to chipping and chunking.
In the following pages there are some of the results of experimental work carried out on ENSACO® Conductive Carbon Blacks in different
rubber compounds.
The data shown here are given as orientation
and are valid for the particular formulations and
sample preparation technique mentioned. Results in other polymers, full studies and publications are available upon request.
Typical applications for ENSACO® Conductive Carbon Black
NBR conductive hose compound
A
B
A
B
Compound
ENSACO® 250
Compound
N-472
Compound
ENSACO® 250
Compound
N-472
NBR NT 3945
100
ENSACO® 250
25
100
N-472
N-550
40
ZnO
Stearic acid
t90% (min)
11.46
11.37
Mooney ML (1+4) at 100° C
45.7
47.2
70.9
72.2
25
Vulcanizate data unaged at RT
40
Shore A Hardness
Stress-strain
4
4
0.5
0.5
Elongation at break (%)
339
311
DOP
30
30
Tensile Strength (MPa)
13.8
14.8
Sulphur
0.4
0.4
Modulus 100% (MPa)
3.9
4.6
Methyl Thuads
2
2
Modulus 300% (MPa)
8.6
10.3
Amax
2
2
Modulus 500% (MPa)
12.6
14.4
79
360
32.4
31.8
Resistivity (Ohm.cm)
By courtesy of Bayer
Tear Strength (N/mm)
Conductive CR conveyor belt cover compound
A
B
A
B
Compound
ENSACO® 250
Compound
N-472
Compound
ENSACO® 250
Compound
N-472
100
100
Dispersion Rating DIK
86.8
85.8
Buna CB 10
2
2
t90% (min)
20.7
21.8
MgO Powder
4
4
Mooney ML(1+4) at 100°C
62
64
62
64
Bayprene 610 (CR)
N-472
30
Vulcanizate data unaged at RT
Shore A hardness
ENSACO® 250
30
Vulkanox DDA
1.5
1.5
Stress-strain
Vulkanox 4020
0.5
0.5
Elongation at break (%)
676
540
Ingralen 450
15
15
Tensile Strength (MPa)
23.4
22.4
ZnO Powder
5
5
Modulus 50% (MPa)
1.2
1.4
Rhenogran ETU-80
0.2
0.2
Modulus 100% (MPa)
2.4
2.7
Stearic acid
0.5
0.5
Modulus 300% (MPa)
9.2
11.5
Modulus 500% (MPa)
16.1
20.6
Compression Set 24h at
70°C (%)
18
19
100
800
By courtesy of Bayer
Resistivity (Ohm.cm)
15
TYpICAL AppLICATIonS FoR EnSACo® ConduCTIvE CARBon BLACk
FkM ConduCTIvE CoMpoundS
1
2
vITon A-32J - Fluoroelastomer
Mgo
Ca(oH)2
3
4
5
6
7
8
9
100
100
100
100
100
100
100
100
100
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
20
-
-
-
-
-
-
20
20
EnSACo® 250G
-
10
20
30
-
-
-
10
20
n-472 SCF
-
-
-
-
10
20
30
-
-
MT black (n990)
vpA-2
1
1
1
1
1
1
1
1
1
Total phr
127.0
117.0
127.0
137.0
117.0
127.0
137.0
137.0
147.0
MT black %
15.7
0.0
0.0
0.0
0.0
0.0
0.0
14.6
13.6
E250G %
0.0
8.5
15.7
21.9
0.0
0.0
0.0
7.3
13.6
SCF N-472 %
0.0
0.0
0.0
0.0
8.5
15.7
21.9
0.0
0.0
Experimental data provided by DuPont Dow Elastomers, Japan
Mooney viscosity ML (1+10’), 100°C
t 90% (min)
20
180
(*)
160
*
18
16
140
14
120
12
100
10
80
8
60
6
40
4
20
2
0
0
1
2
3
4
5
6
7
8
1
9
2
3
4
5
6
8
9
4
5
6
8
9
(*) Rejected because uncurable.
Vulcanizate properties at 177°C for 10 min.
Compression set (%)
Log Resistivity (ohm.cm)
14
70
12
60
10
50
8
40
6
30
4
20
2
10
0
0
1
2
3
4
5
6
8
9
2
3
4
5
6
8
9
Shore A
100
90
80
70
60
50
40
30
20
10
0
1
16
1
2
3
Conductive carbon black is used in semicon
compounds for conductor and insulator shields.
The requirements for those compounds are besides processing, a sufficient electrical conductivity, a smooth or even supersmooth surface
finish, and high purity.
For strippable or easy strippable compounds
these requirements are added to a specific adhesion strength between the insulating layer
and the insulator shield. These strippable or
easy strippable layers have to peeled of by hand
or using a specific peeling device.
Typical polymer compositions are polyolefins or
copolymers; for strippable compounds quite often blends of EVA and NBR are used.
Typical EVA/NBR strippable compounds
Compound
N-472
Compound
ENSACO® 210
Compound
ENSACO® 250
Levaprene 450
90
90
90
Perbunan NT 8625
10
10
10
Rhenogran P60
3
3
3
N-472
40
E 210
40
E 250
40
N-550
40
40
40
Antilux 654
10
10
10
1
1
1
Rhenovin DDA-70
Zn Stearate
1.4
1.4
1.4
Rhenofit TAC/CS
4.3
4.3
4.3
Percadox BC-408
5
5
5
Viscosity ML (4+1)
56
44
48
Rheometer@180 t90%
3.6
3.6
3.8
Mechanical properties
Non aged (diff. aged)
Tensile strength MPa
16.5 (-19)
16.9 (-15)
16.9 (-15)
Elongation at break %
215 (-58)
180 (-50)
170 (-53)
Modulus 100% MPa
Shore A
11
12.2
12.7
87 (+7)
90 (+4)
89 (+7)
4
Peel strength hot air 100°C N
7
3
- after 3 days N
5
4
3
- after 21 days N
5
3
4
210
6600
410
Volume resistivity (Ohm.cm)
Typical EEA/EBA semicon compounds
Compound
EEA
EEA
100
EBA
E 250
Compound
EBA
100
30
30
Resistivity @ RT
7.2
5.6
Resistivity @ 90°C
37
22
Carbon black dispersion: <3µm
97.9
99.4
Die pressure (bar)
229
239
Peroxide
Mixing cond. L/D15; Feed BC; Truput 30
MFI (g/10 min)
23.12
21.39
Specific net mixing energy (KWh/kg)
0.313
0.326
0
0
Protrusion N°/m2
17
Typical applications for ENSACO® Conductive Carbon Black
Power cables and accessories
Self lubricating
polymers
Typical applications for TIMREX® Graphite and Coke
The choice of a polymer-based self lubricating
solid for a particular application depends mainly
upon the operating conditions of: temperature,
chemical environment and the maximum values
of pressure (p) and sliding speed (v). For each
polymer or composite material, a pv limit is quoted, which corresponds to the pressure times the
sliding speed at which the material fails, either
due to unacceptable deformation, or to the high
frictional energy dissipated causes surface melting, softening and excessive wear.
The pv limit of a polymeric material may be increased by increasing its mechanical strength
(resistance to deformation), thermal conductivity (reduction in surface temperatures)
and by decreasing friction (reduces frictional
heating). In practice, thermoplastics (with the
exception of PTFE) are mainly used as pure
solids, since their wear resistance and frictional
coefficient, are satisfactory for most applications. Solid lubricant fillers or fibre reinforcement (glass fibres, carbon fibres, textiles) are
only employed under the more extreme conditions of load and speed.
The major polymers employed as self lubricating solids/composites, are illustrated below.
18
Graphite powder is widely used in polymer
composites, either alone or in combination with
reinforcing fibres, PTFE or various inorganic
fillers, e.g. mica, talc (bottom, right table). Applications include gears, dry sliding bearings,
seals, automotive and micro-mechanical parts.
The properties of graphite which favour its use
in polymer composites are:
• low friction lamellar solid
(reduces friction);
• tendency to form a transfer film on the
countersurface
(assists in wear reduction, particularly when
graphite is applied as water based dispersion
i.e. LB 1300);
• high thermal conductivity
(decreases temperature rise due to frictional
heating);
• electrical conductivity
(prevent build-up of static charge which may
be a problem in some cases);
• chemically inert
(used in conjunction with PTFE in corrosive
environments);
• high thermal stability
(favours use in high temperature applications, e.g. polyimide graphite composites
may be used up to 350°C).
The results described above are thought to be
related to the strength of adhesion at the polymer-graphite interface, which depends upon
the wettability of the powder by the molten polymer, powder surface area to volume ratio, surface chemistry, etc. In simple terms, polystyrene
shows a strong affinity for the graphite surface,
while polyolefins show a weak affinity. Interfacial adhesion increases with increasing powder
surface area to volume ratio, or decreasing particle size.
For this reason relatively fine graphite powders (95%<15 microns) are recommended for
thermoplastics. The strength of thermosetting
polymers is much less sensitive to filler-polymer
interactions, therefore coarser graphite powders may be used (typically 95%<75 microns).
For thermoplastics, the viscosity of the polymer-graphite melt during extrusion/ moulding
will also depend on the graphite particle size,
which should be appropriate. Excessive graphite surface area may also lead to void formation
in the finished composite, due to desorption of
physisorbed vapours in the hot melt.
High graphite purity is generally desirable in order to minimize wear, although this parameter
is unlikely to be important in the presence of
abrasive fillers (glass fibre, carbon fibre).
TYpICAL AppLICATIonS FoR TIMREX® GRApHITE And CokE
0.4
wear
friction
10
0.3
8
6
0.2
4
0.1
friction coefficient
specific wear (m3/Nm)x10-12
12
2
0
0
pure
polystyrene
30%
T 75
50%
T 75
Influence of graphite addition on the specific wear rate and friction of polystyrene
Ball/disc Friction & Wear data: polyamide 6/graphite filler
20
0.4
15
0.3
10
0.2
5
0.1
wear
friction
0
friction coefficient
In the case of polystyrene, addition of 30–50%
of a high purity macrocrystalline synthetic
graphite (T 75), reduced both friction and wear
rate. With polyamide however, addition of a
graphite similar to T 75 reduced the friction
coefficient, but caused a slight increase in the
wear rate, with the finer particle size powder
(KS 6) giving the better result. In the case of
low density polyethylene and polypropylene,
graphite incorporation causes both an increase
in friction and wear.
Ball/disc Friction & Wear data: polystyrene/graphite filler
specific wear (m3/Nm)x10-12
Incorporation of graphite powder into a thermoplastic polymer will generally result in a
reduction in the friction coefficient (with the exception of PTFE) but rarely improves the wear
resistance. This behaviour is illustrated in the
two graphs, which show the mean friction coefficient and specific wear rate for a stainless
steel ball (ø = 5 mm) rubbing on discs of graphite filled polystyrene and polyamide at constant
load (32.5 N) and speed (0.03 m/s). The specific
wear rates of the graphite-polymer composites
were calculated from the diameters of the wear
tracks and the contact geometry.
0
pure
polyamide
30%
KS 6
30%
KS 44
Influence of graphite addition on the specific wear rate and friction of polyamide 6
The above mentioned results are the confirmation that TIMREX® graphite powder is an
excellent additive to produce self-lubricated
polymers. The addition of TIMREX® graphite
powder to the unfilled polymers allow for a reduction of the friction coefficient and in most
of the cases to a reduction of the wear rate.
These results are achieved by a synergic combinations of all the good properties of TIMREX®
graphite powder that among the others are:
the high degree of crystallinity, the extremely
high purity, the optimal texture and the perfect
particle size distribution. All of them linked by
a common factor: the consistency!
19
Filled PTFE
Typical applications for TIMREX® Graphite and Coke
Polytetrafluoroethylene (PTFE) exhibits a very
low coefficient of friction and retains useful mechanical properties at temperatures from -260
to +260 °C for continuous use.
The crystalline melting point is 327 °C, much
higher than that of most other semi-crystalline
polymers. Furthermore, PTFE is nearly inert
chemically and does not adsorb water, leading
to excellent dimensional stability. On the one
hand, these characteristics of PTFE are very
useful in the matrix polymer of polymer-based
composites which are used in sliding applications. On the other hand, PTFE is subjected to
marked cold flow under stress (deformation
and creep) and reveals the highest wear among
the semicrystalline polymers.
However, these disadvantages are very much
improved by incorporating suitable fillers, allowing the use of PTFE in fields otherwise precluded to this polymer.
The treated PTFE is generally known as filledPTFE. There are many kinds of filled- PTFE
composite because various fillers are incorporated into PTFE and one or more materials can
be used simultaneously. Usually, these fillers are
in form of powders or fibers intimately mixed
with the PTFE.
The addition of fillers to the PTFE improves or
modifies its properties depending upon the nature and quantity of filler:
• remarkable increase in wear resistance;
• decrease of deformation under load and of
creep;
• reduction of thermal expansion;
• some types of filler increase the thermal and
electric conductivity.
Filled PTFE is often not as strong and
resilient as virgin PTFE. Sometimes, the filler
limits the resistance to chemical agents and
modify the electrical properties.
20
TIMREX® Graphite
and Coke fillers in filled-PTFE
TIMREX® PC 40-OC Coke
TIMREX PC 40-OC Coke is calcined at high temperatures offering low sulphur concentration,
low content of oversize particles, high apparent
density and high chemical stability against most
chemical substances. TIMREX® PC 40-OC Coke
is added to the virgin PTFE in a percentage by
weight between 10 and 35% along with small
percentage of graphite.
Compounds made of PTFE and TIMREX® PC
40-OC Coke have excellent wear resistance
and deformation strength and compared to the
virgin PTFE, they have practically unchanged
chemical resistance and friction behaviour.
Typical final materials that can be produced
with coke filled PTFE are:
engineering design components, slide bearings,
valve housing and valve seats for chemical applications, piston sealing and guiding elements
for dry-running compressors.
TIMREX® KS44 Synthetic Graphite
NTIMREX® KS 44 is a Primary Synthetic Graphite obtained by the full graphitisation of amorphous carbon materials through the well known
Acheson process. The process parameters in the
Acheson furnace such as temperatures and residential times are all optimised in order to achieve
the perfect degree of crystallinity and the lowest
level of impurities whereas others minor adjustments are made during the material sizing and
conditioning.
The percentage of TIMREX® KS 44 used in the
filled PTFE vary between 5 and 15%.
TIMREX® KS 44 can be used alone or in combination with glass or coke.
TIMREX® KS 44 lowers the coefficient of friction
and is, therefore, often added to other types of
filled PTFE for improving this property (and also
to improve the lifetime of the cutting tools during for instance the production of gaskets and
seals). It improves the deformation under load,
strength and, to a minor degree the wear. Like
coke, it serves well in corrosive environments.
PTFE filled with TIMREX® KS 44 are often used in
steering and shock-absorber gasket, bearings as
well as in slide films for anti-static applications.
Wear resistance
virgin PTFE shows much high wear as a result of
the destruction of the banded structure due to
easy slippage between the crystalline lamellae
in the bands.
The presence of well distributed carbon particles in the filled PTFE partially avoid the slippage between the crystalline lamellae in the
bands and therefore the wear resistance is improved.
Deformation strength
virgin PTFE deformation behaviour is somehow
similar to the mechanism previously described.
In someway the deformation phenomena could
be explained by the tendency of slippage that
occurs between the crystalline lamellae. However, in this case the presence of well distributed
carbon particles in the filled PTFE offers only a
partial explanation to the phenomena because
also hardness of these particles is important in
determine an improvement of the deformation
behaviour.
Friction Coefficient
the coefficient of friction for various filled PTFE
composites is weakly dependent upon the incorporated filler, because a thin PTFE film generally exists at the interface between the body
and counter-body. Consequently the coefficient
of friction is both similar in the filled PTFE and
virgin PTFE. This evidence is true as long as no
oversize particles are present in the filler. In fact
the presence of oversize particles could lead
to a radically modification of the coefficient of
friction. Because of that in carbons as well as in
other fillers is very important the control of oversize particles.
21
Typical applications for TIMREX® Graphite and Coke
Influence of TIMREX®Graphite
and Coke fillers in filled-PTFE
Typical applications for TIMREX® Graphite and Coke
Thermally
conductive polymers
What is thermal conductivity?
The ability of a material to conduct heat is known
as its thermal conductivity. Thermal conductivity itself is nothing else than the transportation
of thermal energy from high to low temperature regions. Thermal energy within a crystalline
solid is conducted by electrons and/or discrete
vibrational energy packets (phonons*). Each effect, phonons and movement of free electrons,
contributes to the rate at which thermal energy
moves. Generally, either free electrons or phonons predominate in the system.
*Phonons
In the crystalline structures of a solid material, atoms excited into higher vibrational frequency impart vibrations into adjacent atoms
via atomic bonds. This coupling creates waves
which travel through the lattice structure of a
material. In solid materials these lattice waves,
or phonons, travel at the velocity of sound.
During thermal conduction it is these waves
which aid in the transport of energy.
Thermal conductivity
of graphite
Graphite is an excellent solution for making
polymers thermally conductive when electrical conductivity is also tolerated. Graphite
operates by a phonon collision mechanism,
very different from the percolation mechanism
occurring with metallic powders. This mechanism, together with the particular morphology
of graphite particles, helps to meet the required thermal conductivity at lower additive
levels without any abrasion issues. In addition,
due to its particular structure, thermal conductivity is different in the different directions
of the crystal. It is highly conducting along
its layers (ab direction or in-plane) and less
conducting perpendicular to the layers (c direction or through-plane) because there is no
bonding between the layers.
In particular, expanded graphite, is well known
as an excellent thermally and electrically conductive additive for polymers. On the way to
graphene, high aspect ratio expanded graphite is thermally more conductive when compared to conventional carbon materials such as
standard graphite and carbon fibres. However,
the very low bulk density of expanded graphite
makes it very difficult to feed into a polymer
melt using common feeding/mixing technologies. In order to overcome the feed issues encountered by compounders with expanded
graphite, TIMCAL has developed a range of
products belonging to the TIMREX® C-THERM™
carbon-based product family.
Grade
Features
Form
Ash
content (%)
Effect on
thermal conductivity
TIMREX®KS family
Standard
(spheroids)
powder
< 0.1
medium
(through-plane +)
TIMREX®SFG family
Standard
(flakes)
powder
< 0.1
medium
(in-plane +)
TIMREX®C-THERM™011
High aspect ratio
(pure)
soft granules
< 2.5
high
TIMREX®C-THERM™001
High aspect ratio
(pure +)
soft granules
< 0.3
high
22
ing the measurement, but also on the type of
polymer, the sample history (type and conditions of compounding and processing) and the
measurement method.
A full set of measurements to determine mechanical properties in PP were performed and
are available to customers. When tested at the
same loadings, C-THERM™ 001/011 imparts
similar mechanical properties as conventional
carbon materials.
4.0
3.5
inj >
TYpICAL AppLICATIonS FoR TIMREX® GRApHITE And CokE
Thermally conductive polymers are able to
evenly distribute heat generated internally
from a device and eliminate “hot spots.” Possible applications for thermally conductive
plastics include heat sinks, geothermal pipes,
LED light sockets, heat exchangers, appliance
temperature sensors and many other industrial
applications. Also thermally conductive elastomers can be found in a wide variety of industrial applications such as gaskets, vibration
dampening, interface materials, and heat sinks.
As highlighted in the figure, the low thermal
conductivity of virgin PPH (~0.38 W/m.K)
could be increased by one order of magnitude already at relatively low addition level
(~3.5 W/m.K at 20% C-THERM™). The “throughplane” thermal conductivity is about the half of
the longitudinal “in-plane” thermal conductivity. These results indicate that the anisotropy
of the graphite particles is conferred to the
final compound, due to their alignment during the injection molding process. This is an
important property that has to be taken into
account by design engineers. Of course the
thermal conductivity strongly depends not
only on the sample orientation (direction) dur-
Thermal Conductivity [W/m.K]
THERMALLY ConduCTIvE poLYMERS
In-plane
In-plane
Through-plane
Through-plane
3.0
2.5
2.0
1.5
1.0
0.5
0
Virgin PPH
20%
ENSACO®
250G
20%
TIMREX®
KS25
20%
TIMREX®
C-THERM™
Timcal locations
production plants
Commercial offices
Distributors present in
many countries. For the
updated list please visit
www.timcal.com
23
Asia-Pacific
Americas
TIMCAL Ltd.
Group Head Office
6743 Bodio
Switzerland
Tel: +41 91 873 20 10
Fax: +41 91 873 20 19
[email protected]
TIMCAL 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
[email protected]
TIMCAL America Inc.
29299 Clemens Road 1-L
Westlake (OH) 44145
USA
Tel: +1 440 871 75 04
Fax: +1 440 871 60 26
[email protected]
TIMCAL Belgium NV/SA
Appeldonkstraat 173
2830 Willebroek
Belgium
Tel: +32 3 886 71 81
Fax: +32 3 886 47 73
[email protected]
TIMCAL Deutschland GmbH
Berliner Allee 47
40212 Düsseldorf
Germany
Tel: +49 211 130 66 70
Fax: +49 211 130 667 13
[email protected]
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
[email protected]
UK Representative Office
Tel: +44 1 270 212 263
Fax: +44 1 270 212 263
[email protected]
www.timcal.com
24
Changzhou TIMCAL
Graphite Corp. Ltd.
188# Taishan Road
Hi-Tech Zone
Changzhou 213022
China
Tel: +86 519 851 008 01
Fax: +86 519 851 013 22
[email protected]
Changzhou TIMCAL
Graphite Corp. Ltd.
Shanghai Branch Office
c/o IMERYS (Shanghai)
288, Jiu Jiang Road
Hong Yi Plaza
Unit 1102-1105
Shanghai 200001
China
Tel: +86 21 613 782 88
Fax: +86 21 613 780 02
[email protected]
Singapore Representative Office
c/o IMERYS Asia Pacific (Singapore)
80 Robinson Road #19-02
068898 Singapore
Tel: +65 67 996 060
Fax: +65 67 996 061
[email protected]
TIMCAL Canada Inc.
990 rue Fernand-Poitras
Terrebonne (QC) J6Y 1V1
Canada
Tel: +1 450 622 91 91
Fax: +1 450 622 86 92
[email protected]
© 2012 TIMCAL Ltd., CH-Bodio. No part of this publication may be reproduced in any form without the prior written authorisation of TIMCAL Ltd.
EUROPE