ASTM D2663-14(2019)
(Test Method)Standard Test Methods for Carbon Black—Dispersion in Rubber
Standard Test Methods for Carbon Black—Dispersion in Rubber
SIGNIFICANCE AND USE
5.1 Visual dispersion ratings correlate with certain important physical properties of the compound. A rating of 5 indicates a state of dispersion developing near maximum properties, while a rating of 1 would indicate a state of dispersion developing considerably depressed properties. Normally, the visual dispersion ratings indicate the following levels of compound quality:
Visual Dispersion Rating
Classification
4 to 5
High
3 to 4
Intermediate
2 to 3
Low
1 to 2
Very low
SCOPE
1.1 These test methods cover the degree of dispersion of carbon black in rubber. Four test methods are described as follows:
Sections
Test Method A—Visual Inspection
3 – 11
Test Method B—Agglomerate Count
12 – 22
Test Method C—Microroughness Measurement
with Profilometer
23 – 33
Test Method D—Microroughness Measurement with IFM
34 – 42
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: D2663 − 14 (Reapproved 2019)
Standard Test Methods for
Carbon Black—Dispersion in Rubber
This standard is issued under the fixed designation D2663; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 ASTM Adjuncts:
Carbon Black Dispersion Standards
1.1 These test methods cover the degree of dispersion of
Carbon Black Dispersion Chart
carbon black in rubber. Four test methods are described as
follows:
TEST METHOD A—VISUAL INSPECTION
Sections
Test Method A—Visual Inspection 3–11 3. Scope
Test Method B—Agglomerate Count 12–22
3.1 Test Method A is a qualitative visual test method.
Test Method C—Microroughness Measurement
with Profilometer 23–33
Ratings are made against a set of standard photographs (Fig.
Test Method D—Microroughness Measurement with IFM 34–42 3
1), andtheresultsareexpressedonanumericalscale.Thistest
1.2 The values stated in SI units are to be regarded as methodcannotbeusedforcompoundsthatcontainfillersother
standard. No other units of measurement are included in this than carbon black.
standard.
4. Summary of Test Method
1.3 This standard does not purport to address all of the
4.1 The compound rubber is torn or cut to expose a fresh
safety concerns, if any, associated with its use. It is the
surface for examination by the eye, aided preferably by a hand
responsibility of the user of this standard to establish appro-
lens or a low-power binocular microscope. The dispersion
priate safety, health, and environmental practices and deter-
level of the carbon black is compared against a series of five
mine the applicability of regulatory limitations prior to use.
photographic standards and then rated numerically from 1
1.4 This international standard was developed in accor-
(very low) to 5 (high) (see Fig. 1).
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
5. Significance and Use
Development of International Standards, Guides and Recom-
5.1 Visual dispersion ratings correlate with certain impor-
mendations issued by the World Trade Organization Technical
tant physical properties of the compound. A rating of 5
Barriers to Trade (TBT) Committee.
indicates a state of dispersion developing near maximum
properties, while a rating of 1 would indicate a state of
2. Referenced Documents
dispersion developing considerably depressed properties.
2.1 ASTM Standards: Normally, the visual dispersion ratings indicate the following
D3182PracticeforRubber—Materials,Equipment,andPro-
levels of compound quality:
cedures for Mixing Standard Compounds and Preparing
Visual Dispersion Rating Classification
Standard Vulcanized Sheets
4to5 High
D4483Practice for Evaluating Precision for Test Method
3 to 4 Intermediate
StandardsintheRubberandCarbonBlackManufacturing
2to3 Low
Industries 1 to 2 Very low
6. Apparatus
6.1 Sharp Knife or Razor Blade.
These test methods are under the jurisdiction of ASTM Committee D24 on
Carbon Black and are the direct responsibility of Subcommittee D24.71 on Carbon
6.2 Hand Lens (10×) or binocular microscope (10 to 20×).
Black Testing in Rubber.
6.3 Illuminator, microscopical-type.
Current edition approved May 1, 2019. Published June 2019. Originally
approved in 1967. Last previous edition approved in 2014 as D2663–14. DOI:
10.1520/D2663-14R19.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from ASTM International Headquarters. Order Adjunct No.
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM ADJD266302. Original adjunct produced in 1967.
Standards volume information, refer to the standard’s Document Summary page on Available from ASTM International Headquarters. Order Adjunct No.
the ASTM website. ADJD266301. Original adjunct produced in 1967.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2663 − 14 (2019)
FIG. 1 Carbon Black Dispersion Standards—Visual Analysis of Torn Vulcanizates
6.4 Knife Heater. 7. Test Specimen
7.1 Vulcanized Compounds—Use a slab of rubber about
6.5 Series of Photographic Standards, rating 1 to 5. These
2mm in thickness. Tear it so that a fresh surface is exposed.
standards give the following percent dispersion ratings by the
The tear may be initiated by a small cut. The most nearly flat
Agglomerate Count Method:
part of the tear is used for rating.
Visual Rating Black Dispersed, %
7.2 Unvulcanized Compounds—Unvulcanized rubber may
be examined as follows:
496 7.2.1 Ifthespecimencontainscuringagents,sheetitoutand
cure in a press to form a vulcanized slab about 2 mm in
D2663 − 14 (2019)
thickness. Mill and cure in accordance with Practice D3182. 10. Report
Then proceed as in 7.1.
10.1 Ratings:
7.2.2 If the specimen contains no curatives, add the appro-
10.1.1 List all ratings, including those on any control
priate materials with a minimum of mixing. Then cure and
compound, on the basis of the 1 to 5 scale defined by the
proceed as above.
standard photographs. Use fractional ratings when necessary.
7.2.3 If the specimen contains no curatives and a dispersion
10.1.2 Average the ratings on different specimens of the
evaluation with no further mixing is required, the compound
same compound as well as the ratings of different operators.
must first be compressed to remove most of the air holes. To
Report the final average values.
accomplish this, press the rubber into a slab between thin
10.2 Compound Identification:
sheets of plastic in a mold at a pressure of about 1.03 kPa for
10.2.1 Formulation—Whenever possible list the following:
5 min at 105°C. Care should be taken to avoid excessive flow
10.2.1.1 Carbon black, type and loading,
during this step. The surface to be examined is formed with a
smooth cutting stroke using a sharp, hot knife (a standard type 10.2.1.2 Other fillers, type and loading,
knife heater may be employed). The most nearly smooth and 10.2.1.3 Polymer type, and
flat part of the cut surface is used for rating.
10.2.1.4 Extender oil, type and loading.
10.2.2 Mixing—Describe the mixing of the compound in
8. Number of Tests
terms of one or more of the following:
8.1 Preferably more than one test (on different tears) should
10.2.2.1 Standard mixing procedure,
be made for each specimen. If convenient, more than one
10.2.2.2 Type of equipment,
operator should rate the samples.
10.2.2.3 Masterbatch,
10.2.2.4 Finished compound (vulcanized), and
9. Procedure
10.2.2.5 Finished compound (unvulcanized).
9.1 Examine the prepared specimens under a hand lens or
binocular microscope (the latter being preferred), with oblique
11. Precision and Bias
illumination to accentuate surface detail. Keep the magnifica-
11.1 No statement is made about either the precision or the
tion and lighting conditions constant for all specimens.
bias of Test Method A since the result is qualitative and not
9.2 Comparethesizeandfrequencyofcarbonagglomerates
applicable to statistical treatment.
inthespecimens(showingupassurfacebumpsordepressions)
to the photographic standards. Then assign the most closely
TEST METHOD B—AGGLOMERATE COUNT
matched numerical rating to each compound being rated. In
borderlinecases,usefractionalratings,forexample,3 ⁄2would
12. Scope
indicate a rating between 3 and 4. In cases of dissimilarity in
12.1 TestMethodBisaquantitativetestmethod.Dispersion
thesizeandfrequencyoftheagglomeratesinthespecimenand
is evaluated by measuring with a light microscope the percent-
those of the standards, the operator shall assign the rating that
age area covered by black agglomerates in microtomed sec-
in his judgment is most applicable. Certain compounds (for
tions of the compound. Since this test method involves direct
example,NRandIR)areparticularlypronetoverysmallblack
measurement, it is quantitative and more accurate than the
agglomerations which are difficult to resolve by the Visual
visual test method. The test is applicable to the analysis of
Inspection Method. In instances of high agglomerate
carbonblackdispersionincompoundsthatcontainotherfillers.
frequency, the surface of stocks of this type may show a
general roughness or fine pebbled appearance. Differences are
13. Summary of Test Method
best resolved at somewhat higher magnification (for example,
13.1 The compounded rubber is microtomed into sections
20×, binocular microscope). If at all possible, examine com-
sufficiently thin to permit observation of the carbon agglom-
pounds of this type also by the agglomerate count method, at
erates by transmitted light, with the aid of a light microscope.
least until sufficient experience is gained to recognize disper-
The total cross-sectional area of all agglomerates 5 µm or
sion differences with the Visual Inspection Method.
larger is counted, and from the known content of carbon black
9.3 In comparing a series of different compounds, it is also
in the stock, the percentage of carbon black below the 5-µm
desirable to rate the specimens side by side rather than one at
size is calculated and expressed as “Percentage of Carbon
a time. This use of a control compound is also advisable. This
Black Dispersed.”
is best prepared by individual operators, since dispersion
requirements may vary greatly for different types of com-
14. Significance and Use
pounds. The control sample should represent a minimum
acceptable dispersion level for the type of compound being 14.1 Certainimportantphysicalpropertiesofthecompound
rated. Because it can be observed side by side with unknown are influenced significantly by the degree of carbon black
samples under identical conditions, a control compound is dispersion within the compound (for example, tensile strength
more accurate than the photographic standards in discerning and abrasion resistance). The correlation of these properties
small deviations from what is considered the norm for a with the percentage dispersion determined by theAgglomerate
specific type of compound. Prepare a fresh surface on the Count Method approximates the following pattern for many
control as often as necessary to ensure cleanliness. types of black loaded rubber compounds:
D2663 − 14 (2019)
FIG. 2 Rotary Microtome with Cryogenic Attachment for Sectioning Rubber Specimens
15.3 Microscope—An optical microscope with binocular
Dispersion, % Classification
viewing and digital image capture is recommended. This
Above 99 Very high
should include a movable specimen stage and white light
97 to 99 High
95 to 97 Intermediate source with variable intensity. Lenses should include two 10×
92 to 95 Low
widefieldeyepiecesandobjectivesintherangefrom6to10×.
Below 92 Very low
Taking into account microscope tube corrections, objectives
should be selected so that magnifications in the range from 75
15. Apparatus
to 100× are available. (See Fig. 3.)
15.1 Microtome—A rotary microtome capable of produc-
15.4 Computer—Acomputer should be available and inter-
ing sections from samples up to 3 mm in cross-section and 1
facedtothedigitalcameraonthemicroscopetocapturedigital
cm in length. Tungsten carbide knives are recommended. (See
photomicrographs of the specimens. (See Fig. 3.)
Fig. 2.)
15.5 Image Analysis Software—Suitable image analysis
15.2 Cryogenic Cooling Unit—A cryogenic cooling attach-
software to allow thresholding of the captured micrographs,
ment for the above rotary microtome capable of cooling the
conversionofthethresholdedimagetobinaryandareafraction
sample to –160°C. (See Fig. 2.)
determinationfromthebinaryimages.Examplesofthistypeof
software include, but are not limited to, Image J, ImagePro,
NIH Image, IDL, and NIST Lispix.
Example, Leica RM2265.
Example, Leica LN22. 15.6 Razor Blades.
D2663 − 14 (2019)
FIG. 3 Light Microscope Equipped with Digital Camera and Computer System
15.7 Sable Brushes (00). zinc oxide, with a cure of 1 h at 155°C. Other alternative
approaches for curing high unsaturation polymers without
15.8 Microscope Slides and Cover Glasses.
actually mixing in curatives are (1) high-energy radiation and
(2) chemical treatment with sulfur monochloride. However,
16. Reagents and Materials
before using either of these latter methods, the stock should be
16.1 Liquid Nitrogen.
pressed out to eliminate most of the air holes. Cure in
16.2 Organic Solvents—Appropriateorganicliquidtoaidin
accordance with Practice D3182.
flattening section onto the glass microscope slides. Examples
include xylenes, toluene, and methanol.
18. Test Specimen
18.1 Cut out a specimen approximately 1 cm long, 1 cm
17. Sampling
wide, and approximately 2-mm deep.
17.1 Vulcanizates—Specimens may be cut from standard
test sheets (about 2-mm thick) or from pieces of actual cured 18.2 Cut the square block into a trapezoidal shape that will
articles. Vulcanized samples must be employed because of the fit the sample chuck on the rotary microtome.
solvent used to uncurl the thin sections. If pieces other than
18.3 Prepare one specimen block for each different com-
2-mm sheets are used, they should first be cut down to a
pound to be examined.
thickness of about 2 to 3 mm.
17.2 Unvulcanized Compounds—For rubbers of high un-
19. Procedure
saturation(forexample,OE-SBR,NR,andBR),dustsmallbits
19.1 Microtome Preparation—Turn on the rotary
(enoughsubsequentlytoformbuttonsabout10mmindiameter
microtome, insert the knife into the microtome and adjust to
and about 2 to 3-mm deep) thoroughly with dicumyl peroxide.
the correct cutting angle (see microtome manufacturer instruc-
Cure in a button mold under high pressure at about 155°C.
tions). Fill the liquid nitrogen dewar and attach to the cryo-
OE-SBR rubbers require about 30 to 60-min cure. BR requires
genicchamberonthemicrotome.Coolthemicrotomechamber
about 10 to 15-min cure. After cure, scrape off the excess
and knife holder.
peroxide from the sample surface and proceed with sectioning
19.2 Sample Preparation—Insert the prepared specimen
inthestandardmanner,takingcarenottoparedownbelowthe
block into the microtome chuck and insert the chuck into the
cured surface layer.
microtomesuchthatthelongaxisofthespecimenisparallelto
17.2.1 For IIR, satisfactory surface cures can be obtained
the cutting direction. Cool the sample to approximately 50°C
with a mixture of 1 part tetramethylthiuram disulfide (TMTD),
below the elastomer glass transition temperature.
1partmercaptobenzothiazole(MBT),1partsulfur,and5parts
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D2663 − 14 D2663 − 14 (Reapproved 2019)
Standard Test Methods for
Carbon Black—Dispersion in Rubber
This standard is issued under the fixed designation D2663; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 These test methods cover the degree of dispersion of carbon black in rubber. Four test methods are described as follows:
Sections
Test Method A—Visual Inspection 3 – 11
Test Method B—Agglomerate Count 12 – 22
Test Method C—Microroughness Measurement
with Profilometer 23 – 33
Test Method D—Microroughness Measurement with IFM 34 – 42
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D3182 Practice for Rubber—Materials, Equipment, and Procedures for Mixing Standard Compounds and Preparing Standard
Vulcanized Sheets
D4483 Practice for Evaluating Precision for Test Method Standards in the Rubber and Carbon Black Manufacturing Industries
2.2 ASTM Adjuncts:
Carbon Black Dispersion Standards
Carbon Black Dispersion Chart
TEST METHOD A—VISUAL INSPECTION
3. Scope
3.1 Test Method A is a qualitative visual test method. Ratings are made against a set of standard photographs (Fig. 1), and the
results are expressed on a numerical scale. This test method cannot be used for compounds that contain fillers other than carbon
black.
3. Scope
3.1 Test Method A is a qualitative visual test method. Ratings are made against a set of standard photographs (Fig. 1), and the
results are expressed on a numerical scale. This test method cannot be used for compounds that contain fillers other than carbon
black.
These test methods are under the jurisdiction of ASTM Committee D24 on Carbon Black and are the direct responsibility of Subcommittee D24.71 on Carbon Black
Testing in Rubber.
Current edition approved Jan. 1, 2014May 1, 2019. Published February 2014June 2019. Originally approved in 1967. Last previous edition approved in 20082014 as
D2663 – 08.D2663 – 14. DOI: 10.1520/D2663-14.10.1520/D2663-14R19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from ASTM International Headquarters. Order Adjunct No. ADJD266302. Original adjunct produced in 1967.
Available from ASTM International Headquarters. Order Adjunct No. ADJD266301. Original adjunct produced in 1967.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2663 − 14 (2019)
FIG. 1 Carbon Black Dispersion Standards—Visual Analysis of Torn Vulcanizates
4. Summary of Test Method
4.1 The compound rubber is torn or cut to expose a fresh surface for examination by the eye, aided preferably by a hand lens
or a low-power binocular microscope. The dispersion level of the carbon black is compared against a series of five photographic
standards and then rated numerically from 1 (very low) to 5 (high) (see Fig. 1).
5. Significance and Use
5.1 Visual dispersion ratings correlate with certain important physical properties of the compound. A rating of 5 indicates a state
of dispersion developing near maximum properties, while a rating of 1 would indicate a state of dispersion developing considerably
depressed properties. Normally, the visual dispersion ratings indicate the following levels of compound quality:
D2663 − 14 (2019)
Visual Dispersion Rating Classification
4 to 5 High
3 to 4 Intermediate
2 to 3 Low
1 to 2 Very low
6. Apparatus
6.1 Sharp Knife or Razor Blade.
6.2 Hand Lens (10×) or binocular microscope (10 to 20×).
6.3 Illuminator, microscopical-type.
6.4 Knife Heater.
6.5 Series of Photographic Standards, rating 1 to 5. These standards give the following percent dispersion ratings by the
Agglomerate Count Method:
Visual Rating Black Dispersed, %
1 70
2 80
3 91
4 96
5 99
7. Test Specimen
7.1 Vulcanized Compounds—Use a slab of rubber about 2 mm in thickness. Tear it so that a fresh surface is exposed. The tear
may be initiated by a small cut. The most nearly flat part of the tear is used for rating.
7.2 Unvulcanized Compounds—Unvulcanized rubber may be examined as follows:
7.2.1 If the specimen contains curing agents, sheet it out and cure in a press to form a vulcanized slab about 2 mm in thickness.
Mill and cure in accordance with Practice D3182. Then proceed as in 7.1.
7.2.2 If the specimen contains no curatives, add the appropriate materials with a minimum of mixing. Then cure and proceed
as above.
7.2.3 If the specimen contains no curatives and a dispersion evaluation with no further mixing is required, the compound must
first be compressed to remove most of the air holes. To accomplish this, press the rubber into a slab between thin sheets of plastic
in a mold at a pressure of about 1.03 kPa for 5 min at 105°C. Care should be taken to avoid excessive flow during this step. The
surface to be examined is formed with a smooth cutting stroke using a sharp, hot knife (a standard type knife heater may be
employed). The most nearly smooth and flat part of the cut surface is used for rating.
8. Number of Tests
8.1 Preferably more than one test (on different tears) should be made for each specimen. If convenient, more than one operator
should rate the samples.
9. Procedure
9.1 Examine the prepared specimens under a hand lens or binocular microscope (the latter being preferred), with oblique
illumination to accentuate surface detail. Keep the magnification and lighting conditions constant for all specimens.
9.2 Compare the size and frequency of carbon agglomerates in the specimens (showing up as surface bumps or depressions)
to the photographic standards. Then assign the most closely matched numerical rating to each compound being rated. In borderline
cases, use fractional ratings, for example, 3 ⁄2 would indicate a rating between 3 and 4. In cases of dissimilarity in the size and
frequency of the agglomerates in the specimen and those of the standards, the operator shall assign the rating that in his judgment
is most applicable. Certain compounds (for example, NR and IR) are particularly prone to very small black agglomerations which
are difficult to resolve by the Visual Inspection Method. In instances of high agglomerate frequency, the surface of stocks of this
type may show a general roughness or fine pebbled appearance. Differences are best resolved at somewhat higher magnification
(for example, 20×, binocular microscope). If at all possible, examine compounds of this type also by the agglomerate count
method, at least until sufficient experience is gained to recognize dispersion differences with the Visual Inspection Method.
9.3 In comparing a series of different compounds, it is also desirable to rate the specimens side by side rather than one at a time.
This use of a control compound is also advisable. This is best prepared by individual operators, since dispersion requirements may
vary greatly for different types of compounds. The control sample should represent a minimum acceptable dispersion level for the
type of compound being rated. Because it can be observed side by side with unknown samples under identical conditions, a control
compound is more accurate than the photographic standards in discerning small deviations from what is considered the norm for
a specific type of compound. Prepare a fresh surface on the control as often as necessary to ensure cleanliness.
D2663 − 14 (2019)
10. Report
10.1 Ratings:
10.1.1 List all ratings, including those on any control compound, on the basis of the 1 to 5 scale defined by the standard
photographs. Use fractional ratings when necessary.
10.1.2 Average the ratings on different specimens of the same compound as well as the ratings of different operators. Report
the final average values.
10.2 Compound Identification:
10.2.1 Formulation—Whenever possible list the following:
10.2.1.1 Carbon black, type and loading,
10.2.1.2 Other fillers, type and loading,
10.2.1.3 Polymer type, and
10.2.1.4 Extender oil, type and loading.
10.2.2 Mixing—Describe the mixing of the compound in terms of one or more of the following:
10.2.2.1 Standard mixing procedure,
10.2.2.2 Type of equipment,
10.2.2.3 Masterbatch,
10.2.2.4 Finished compound (vulcanized), and
10.2.2.5 Finished compound (unvulcanized).
11. Precision and Bias
11.1 No statement is made about either the precision or the bias of Test Method A since the result is qualitative and not
applicable to statistical treatment.
TEST METHOD B—AGGLOMERATE COUNT
12. Scope
12.1 Test Method B is a quantitative test method. Dispersion is evaluated by measuring with a light microscope the percentage
area covered by black agglomerates in microtomed sections of the compound. Since this test method involves direct measurement,
it is quantitative and more accurate than the visual test method. The test is applicable to the analysis of carbon black dispersion
in compounds that contain other fillers.
12. Scope
12.1 Test Method B is a quantitative test method. Dispersion is evaluated by measuring with a light microscope the percentage
area covered by black agglomerates in microtomed sections of the compound. Since this test method involves direct measurement,
it is quantitative and more accurate than the visual test method. The test is applicable to the analysis of carbon black dispersion
in compounds that contain other fillers.
13. Summary of Test Method
13.1 The compounded rubber is microtomed into sections sufficiently thin to permit observation of the carbon agglomerates by
transmitted light, with the aid of a light microscope. The total cross-sectional area of all agglomerates 5 μm or larger is counted,
and from the known content of carbon black in the stock, the percentage of carbon black below the 5-μm size is calculated and
expressed as “Percentage of Carbon Black Dispersed.”
14. Significance and Use
14.1 Certain important physical properties of the compound are influenced significantly by the degree of carbon black dispersion
within the compound (for example, tensile strength and abrasion resistance). The correlation of these properties with the percentage
dispersion determined by the Agglomerate Count Method approximates the following pattern for many types of black loaded
rubber compounds:
Dispersion, % Classification
Above 99 Very high
97 to 99 High
95 to 97 Intermediate
92 to 95 Low
Below 92 Very low
D2663 − 14 (2019)
FIG. 2 Rotary Microtome with Cryogenic Attachment for Sectioning Rubber Specimens
15. Apparatus
15.1 Microtome—A rotary microtome capable of producing sections from samples up to 3 mm in cross-section and 1 cm in
length. Tungsten carbide knives are recommended. (See Fig. 2.)
15.2 Cryogenic Cooling Unit—A cryogenic cooling attachment for the above rotary microtome capable of cooling the sample
to –160°C. (See Fig. 2.)
15.3 Microscope—An optical microscope with binocular viewing and digital image capture is recommended. This should
include a movable specimen stage and white light source with variable intensity. Lenses should include two 10× wide field
eyepieces and objectives in the range from 6 to 10×. Taking into account microscope tube corrections, objectives should be selected
so that magnifications in the range from 75 to 100× are available. (See Fig. 3.)
15.4 Computer—A computer should be available and interfaced to the digital camera on the microscope to capture digital
photomicrographs of the specimens. (See Fig. 3.)
15.5 Image Analysis Software—Suitable image analysis software to allow thresholding of the captured micrographs, conversion
of the thresholded image to binary and area fraction determination from the binary images. Examples of this type of software
include, but are not limited to, Image J, ImagePro, NIH Image, IDL, and NIST Lispix.
Example, Leica RM2265.
Example, Leica LN22.
D2663 − 14 (2019)
FIG. 3 Light Microscope Equipped with Digital Camera and Computer System
15.6 Razor Blades.
15.7 Sable Brushes (00).
15.8 Microscope Slides and Cover Glasses.
16. Reagents and Materials
16.1 Liquid Nitrogen.
16.2 Organic Solvents—Appropriate organic liquid to aid in flattening section onto the glass microscope slides. Examples
include xylenes, toluene, and methanol.
17. Sampling
17.1 Vulcanizates—Specimens may be cut from standard test sheets (about 2-mm thick) or from pieces of actual cured articles.
Vulcanized samples must be employed because of the solvent used to uncurl the thin sections. If pieces other than 2-mm sheets
are used, they should first be cut down to a thickness of about 2 to 3 mm.
17.2 Unvulcanized Compounds—For rubbers of high unsaturation (for example, OE-SBR, NR, and BR), dust small bits (enough
subsequently to form buttons about 10 mm in diameter and about 2 to 3-mm deep) thoroughly with dicumyl peroxide. Cure in a
button mold under high pressure at about 155°C. OE-SBR rubbers require about 30 to 60-min cure. BR requires about 10 to
15-min cure. After cure, scrape off the excess peroxide from the sample surface and proceed with sectioning in the standard
manner, taking care not to pare down below the cured surface layer.
17.2.1 For IIR, satisfactory surface cures can be obtained with a mixture of 1 part tetramethylthiuram disulfide (TMTD), 1 part
mercapt
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Questions, Comments and Discussion
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