Carbon Black Manufacture, Testing,

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Carbon BlackManufacture, Testing, Effect
onRubber Properties

• Joel Neilsen
• Sid Richardson Carbon Energy Co.
• July 24, 2006

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A Brief History of Carbon Filler

• 300 B.C. - Flame soot used in Asia for
  pigmentation
• 1830 - Lamp black patented for NR reinforcement
• 1880s - Channel Blacks in production
• 1904 - Carbon Black found to be excellent
  reinforcement for NR
• 1915 - General public acceptance of black tires
• 1920s Thermal Black process discovered
• Furnace Black
• Gas Process 1922
• Oil Process 1942

Modern Tire Industry Uses Oil Furnace Black
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Yesterday
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Today
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Furnace Process
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What is Carbon Black?
Definition Material consisting essentially of
elemental carbon in the form of nearspherical
particles coalesced into aggregates (smallest
dispersible entity) of colloidal size, obtained
by partial combustion of hydrocarbons.
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Model
Carbon Black Formation
Amorphous Carbon Due to Incomplete Dehydrogenation
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Particles, Aggregates, Agglomerates
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Physical Characteristics

• Specific Surface Area the exposed surface area
  (m2) of the material per unit mass (g).
  Correlated to microstructure, particle size, and
  rubber hysteresis.
• Structure a term used to describe the degree of
  irregularity and deviation from sphericity of the
  shape of a carbon black aggregate. Correlated to
  aggregate size/shape and rubber processing
  strength properties.
• Density mass per unit volume (1.8 2.0 g/cm3
  depending on technique.)

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Examples of Carbon Black Morphology
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STRUCTURE SURFACE AREA RELATIONSHIP
Rev. 04/06
Structure OAN
Surface Area Nitrogen Adsorption Number
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Nitrogen Surface Area (N2SA)
BET Method N2 gas adsorption at liquid N2
temperatures at several partial pressures of N2.
BET theory applied to give total exposed surface
area (m2/g). STSA Method similar to above but
at higher partial pressure so that de Boer theory
can be applied to give an external surface area
devoid of micropores. Normal furnace blacks have
few, if any, micropores.
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Iodine Number
I2 adsorbed onto carbon black from I2/KI
solution. Excess Iodine titrated with Na2S2O3.
Units g I2/Kg Carbon Black. Fast, easy test in
general agreement with N2SA. However, presence of
volatiles, surface porosity, or extractables
influence the result.
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Oil Absorption Number (OAN)
Paraffin oil is added to carbon black in a mixing
chamber until all interstices between aggregates
are filled and a change is observed, from free
flowing powder to semi-plastic agglomeration
(increase in viscosity detected as endpoint).
Easily manipulated in carbon black process by
work applied to carbon black. (Formerly known as
DBP.)
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COAN or 24M4
Compressed Oil Absorption Number same as Oil
Absorption Number except sample is crushed to
24,000 psi 4 times before testing. Value is set
in carbon black reactor.
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Tinting Strength
Value derived from reflectance of a paste of
carbon black with Zinc oxide in oil and is
referenced to an N330 carbon black. ? Sp Surface
area ? Tint ? Structure ?Tint Measures ability
of carbon black to darken a paste not a primary
property and only related to rubber properties
because of relationships above. Not necessary for
specifications.
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Impurities in Carbon Black

• Moisture water left after drying or adsorbed
  post production (1.0-1.5).
• Ash Content non-carbon components present after
  combustion, primarily due to inorganic salts in
  process water (0.75-1.0).
• Toluene Extractables measures residual oil on
  surface, useful in controlling reaction processes
  for production.
• Metal Content Iron from production equipment,
  various metals from feedstock or additives (ppm
  level).
• Sulfur Content arising from feedstock,
  chemically bound.
• Sieve Residue water wash sieve residue
  (generally 35 and 325 sieves). Primarily coke,
  refractory or metal (0.001 and 0.1 respectively).

Impurity levels are generally very low.
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Pellet Property Testing of Carbon Black
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What is a Carbon Black Pellet?
2mm
A relatively large agglomerate mass (physically
bound and entangled aggregates) that has been
densified in spheroidal form to facilitate
handling and processing
A single pellet may contain 1012 - 1014
aggregates in a single pellet (depending on
grade, pellet size).
0.2µm
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Pellet Characteristics

• Pellet Hardness
• Pellet Size Distribution
• Fines (5 20)
• Pellet Stability (Attrition)
• Mass Strength

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Test Procedure - Pellet Hardness(ASTM D3313 or
D5230)

• Test for hardness on 20-50 pellets using
  Sweigart tester

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Test Procedure - Pellet Hardness(ASTM D3313 or
D5230)

• Test for hardness on 20-50 pellets using
  automated tester (Titan or HiTec)

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Automated Pellet Hardness Testers Criteria for
Break (Hardness Endpoint)

• Reduction in pellet diameter
• Gram - force drop

Pellet reduced to 90 of original
diameter ? endpoint
Load Cell Pellet Piston
3 gram-force drop from one step to next in piston
movement ? endpoint
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Pellet Size Distribution
100 g sample placed in top pan and whole stack
shaken for 1 minute to determine distribution of
pellet sizes.
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5 Fines

• Similar to PSD, but 25 g sample is shaken over
  0.125 mm screen (US 120) for 5 min.
• Will Include
• Unpelleted loose black
• Soft cake
• Exploded pellets
• Degraded outer layers of unstable pellets

Best single test for flow properties in most
cases.
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Mass Strength

• A measure of the tendency for carbon black
  pellets to pack together and to influence flow in
  a bulk handling system.
• Carbon black pellets are poured into a cylinder
  of defined dimensions and force is applied for 10
  seconds in order to determine the minimum force
  required to cause the carbon black to pack
  (evidenced by formation of a ring or bridge of
  pressed carbon black in the cylinder).

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Carbon Black Dispersion in Rubber
Key tire performance characteristics improved by
increased polymer-filler interaction and micro
dispersion
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Carbon Black - Rubber Mixing Steps

• Mechanical Effect ? Breakdown of Original Pellets
  ? Shear Forces in the Mixer
• Subsequent Dispersion (micro) ? Role of Polymer /
  Filler Interaction

Importance of Carbon Black Dispersion Cannot be
Overstated!
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Carbon Black Mixing Steps
Pellet
Aggregate/Agglomerate
Sub-Pellets
Incorporation
Disintegration
Dispersion
Undispersed Sub-Pellet
Submicron Dispersion is Critical
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Carbon Black Dispersion Measurement
Dispersion A scale dependent parameter
?Submicron Dispersion ?Performance
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ASTM Dispersion Tests

• Test Method A Visual Inspection
• Compares sample with photographic standards
• Qualitative in nature
• Test Method B Agglomerate Count
• Uses optical microscopy to count agglomerates
• Can quantify agglomerates gt 5 um
• Test Method C Microroughness, MSM
• Also quantitative, but smaller scale (gt 2.5 um)

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ASTM Method
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Agglomerate Counting

• Vulcanized rubber is frozen with liquid N2 and
  cut with a microtome (glass blade) into several
  thin sections ca. 2 um thick.
• Sections are mounted on a brass grid and examined
  by light microscope with graticule (at 100X, each
  square 10 x 10 um.)
• Holes at least half-covered by agglomerates are
  totaled to count all agglomerates gt 5 um.

Very Time-Consuming and Somewhat Subjective
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Microroughness - Mechanical Scanning Microscope
(MSM)
2 µm Diamond stylus
Lower Surface Microroughness, Ra Better
Dispersion
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Electrical Measurements
Polymers
Carbon Black
Very High Resistivity
Very Low Resistivity
AC and DC Measurements
SID RICHARDSONCARBON CO.
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Results Variable Loading (E-SBR, N330)
Ep
Electrical Percolation Point (Ep)
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Reflectometry
Principle Carbon black - Absorption Polymer -
Reflection / Diffusion
Reflectometry - Promising Sub-micron Dispersion
Test for Uncured Rubber Compounds Possibility of
On-line Dispersion Measurements
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Carbon Black Influence on Rubber Properties

• Two Experiments
• Increasing Structure (surface area constant)
• Increasing Surface Area (Structure constant)

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EPDM Compounding Study

• ASTM Recipe 2 for EPDM (100 phr black, 75 phr
  oil)
• EPDM ML 14 _at_ 125 C 55, 2.3 ENB
• Carbon Black Grades Evaluated
• Equivalent surface area (iodine) vs. increasing
  structure (DBP) N326 vs. N330 vs. N358
• Equivalent surface area vs. increasing structure
  N660 vs. N650
• Equivalent structure vs. increasing surface area
  N650, N351, N339

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Comparison 1
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Comparison 2
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Comparison 3
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N100 Series

• N110, NSA 127, OAN 113
• Excellent Abrasion Resistance, Reinforcement,
  Tensile Strength
• Passenger Tire Treads
• N134, NSA 143, OAN 127
• Excellent Tensile Strength, Superior Abrasion
  Resistance
• Passenger and Truck Tire Treads

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N200 Series

• N220, NSA 119, OAN 114
• Excellent Abrasion, Tensile, Tear
• Passenger and Truck Tires, MRG
• N234, NSA 119, OAN 125
• Even Better Abrasion, Wear, Extrusion
• High Performance Tires, Retreads
• N231, NSA 111, OAN 92
• High Abrasion, Excellent Tear Resistance
• Good for Off Road Tires when Tear is Important

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N300 Series

• N330, NSA 78, OAN 102
• Good Abrasion, Tensile, Tear, Processing
• General Filler for Wide Range of Tire MRGs
• N326, NSA 78, OAN 72
• Good Reinforcement, Better Tensile Tear
• Carcass, Belt Skim, Steel Cord Applications
• N339, NSA 91, OAN 120
• Superior Abrasion, Extrusion, Hysteresis
• Tire Treads, High-Stress MRGs

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Carcass N500, N600, N700

• N550, NSA 40, OAN 121
• OK Abrasion, High Strength, Low Die Swell
• Extruded Parts, Tread Base, Tire Carcass
• N660, NSA 35, OAN 90
• Low Modulus Viscosity, Good Heat Resistance
• Carcass, Tubes, Belts, Hoses
• N762, NSA 29, OAN 65
• Good Processing at High Loads
• Tire Bead Insulation, Hoses, Belts

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Average percent weight of carbon black in PCT
components
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Typical Tire Components

• Tread N100-N300
• Shoulder N300/N550
• Sidewalls N550, N650
• Belts N326, N330
• Plies N660
• Liner N660
• Bead N351
• Chafer N326

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SID RICHARDSONCARBON CO.
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