ASTM D2663-95a(2000)
(Test Method)Standard Test Methods for Carbon Black-Dispersion in Rubber
Standard Test Methods for Carbon Black-Dispersion in Rubber
SCOPE
1.1 These test methods determine the degree of dispersion of carbon black in rubber. Three test methods are described as follows: Sections Test Method A-Visual Inspection 3 to 11 Test Method B-Agglomerate Count 12 to 23 Test Method C-Microroughness Measurement 24 to 34
1.2 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.
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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D2663–95a (Reapproved 2000)
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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4. Summary of Test Method
1.1 These test methods determine the degree of dispersion 4.1 The compound rubber is torn or cut to expose a fresh
of carbon black in rubber. Three test methods are described as surface for examination by the eye, aided preferably by a hand
follows: lens or a low-power binocular microscope. The dispersion
level of the carbon black is compared against a series of five
Sections
Test Method A—Visual Inspection 3-11
photographic standards and then rated numerically from 1
Test Method B—Agglomerate Count 12-23
(very low) to 5 (high) (see Fig. 1).
Test Method C—Microroughness Measurement 24-34
1.2 The values stated in SI units are to be regarded as the 5. Significance and Use
standard. The values in parentheses are for information only.
5.1 Visual dispersion ratings correlate with certain impor-
1.3 This standard does not purport to address all of the
tant physical properties of the compound. A rating of 5
safety concerns, if any, associated with its use. It is the
indicates a state of dispersion developing near maximum
responsibility of the user of this standard to establish appro-
properties, while a rating of 1 would indicate a state of
priate safety and health practices and determine the applica-
dispersion developing considerably depressed properties. Nor-
bility of regulatory limitations prior to use.
mally, the visual dispersion ratings indicate the following
levels of compound quality:
2. Referenced Documents
Visual Dispersion Rating Classification
2.1 ASTM Standards:
4to5 High
D1765 Classification System for Carbon Blacks Used in
2 3 to 4 Intermediate
Rubber Products
2to3 Low
D3051 PracticeforCarbonBlack—StatingthePrecisionof
1 to 2 Very low
ASTM Test Methods
6. Apparatus
D3182 Practice for Rubber—Materials, Equipment, and
6.1 Sharp Knife or Razor Blade.
Procedures for Mixing Standard Compounds and Prepar-
ing Standard Vulcanized Sheets 6.2 Hand Lens (103)orbinocularmicroscope(10to203).
6.3 Illuminator, microscopical-type.
D3396 Practice for Carbon Black—Measuring the Preci-
sion of ASTM Test Methods 6.4 Knife Heater.
6.5 Series of Photographic Standards, rating 1 to 5. These
TEST METHOD A—VISUAL INSPECTION
standards give the following percent dispersion ratings by the
Agglomerate Count Method:
3. Scope
Visual Rating Black Dispersed, %
3.1 Test Method A is a qualitative visual test method.
Ratings are made against a set of standard photographs (Fig.
1), andtheresultsareexpressedonanumericalscale.Thistest
methodcannotbeusedforcompoundsthatcontainfillersother
than carbon black.
7. Test Specimen
7.1 Vulcanized Compounds—Use a slab of rubber about 2
These test methods are under the jurisdiction of ASTM Committee D24 on
mm in thickness.Tear it so that a fresh surface is exposed.The
Carbon Black and are the direct responsibility of Subcommittee D24.71 on Carbon
tear may be initiated by a small cut. The most nearly flat part
Black Testing in Rubber.
of the tear is used for rating.
Current edition approved Oct. 10, 1995. Published December 1995. Originally
published as D2663–67T. Last previous edition D2663–95.
7.2 Unvulcanized Compounds—Unvulcanized rubber may
Annual Book of ASTM Standards, Vol 09.01.
be examined as follows:
A separate 8 by 10-in. glossy print of Fig. 1 is available at a nominal charge
fromASTMHeadquarters,1916RaceSt.,Philadelphia,PA19103.RequestAdjunct
No. 12-426630-20.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D2663–95a (2000)
FIG. 1 Carbon Black Dispersion Standards—Visual Analysis of Torn Vulcanizates
7.2.1 Ifthespecimencontainscuringagents,sheetitoutand 7.2.3 If the specimen contains no curatives and a dispersion
cure in a press to form a vulcanized slab about 2 mm in evaluation with no further mixing is required, the compound
thickness. Mill and cure in accordance with Practice D3182. must first be compressed to remove most of the air holes. To
Then proceed as in 7.1. accomplish this, press the rubber into a slab between thin
7.2.2 If the specimen contains no curatives, add the appro- sheets of plastic in a mold at a pressure of about 1.03 kPa for
priate materials with a minimum of mixing. Then cure and 5 min at 105°C. Care should be taken to avoid excessive flow
proceed as above. during this step. The surface to be examined is formed with a
D2663–95a (2000)
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:
10.2.2.1 Standard mixing procedure,
8.1 Preferably more than one test (on different tears) should
10.2.2.2 Type of equipment,
be made for each specimen. If convenient, more than one
10.2.2.3 Masterbatch,
operator should rate the samples.
10.2.2.4 Finished compound (vulcanized), and
10.2.2.5 Finished compound (unvulcanized).
9. Procedure
9.1 Examine the prepared specimens under a hand lens or
11. Precision and Bias
binocular microscope (the latter being preferred), with oblique
11.1 No statement is made about either the precision or the
illumination to accentuate surface detail. Keep the magnifica-
bias of Test Method A since the result is qualitative and not
tion and lighting conditions constant for all specimens.
applicable to statistical treatment.
9.2 Comparethesizeandfrequencyofcarbonagglomerates
inthespecimens(showingupassurfacebumpsordepressions)
TEST METHOD B—AGGLOMERATE COUNT
to the photographic standards. Then assign the most closely
matched numerical rating to each compound being rated. In
12. Scope
borderlinecases,usefractionalratings,forexample,3 ⁄2would
12.1 TestMethodBisaquantitativetestmethod.Dispersion
indicate a rating between 3 and 4. In cases of dissimilarity in
is evaluated by measuring with a light microscope the percent-
thesizeandfrequencyoftheagglomeratesinthespecimenand
age area covered by black agglomerates in microtomed sec-
those of the standards, the operator shall assign the rating that
tions of the compound. Since this test method involves direct
in his judgment is most applicable. Certain compounds (for
measurement, it is quantitative and more accurate than the
example,NRandIR)areparticularlypronetoverysmallblack
visual test method. The test is applicable to the analysis of
agglomerations which are difficult to resolve by the Visual
carbonblackdispersionincompoundsthatcontainotherfillers.
Inspection Method. In instances of high agglomerate fre-
quency, the surface of stocks of this type may show a general
13. Summary of Test Method
roughness or fine pebbled appearance. Differences are best
13.1 The compounded rubber is microtomed into sections
resolvedatsomewhathighermagnification(forexample,203,
sufficiently thin to permit observation of the carbon agglom-
binocular microscope). If at all possible, examine compounds
erates by transmitted light, with the aid of a light microscope.
ofthistypealsobytheagglomeratecountmethod,atleastuntil
The total cross-sectional area of all agglomerates 5 µm or
sufficient experience is gained to recognize dispersion differ-
larger is counted, and from the known content of carbon black
ences with the Visual Inspection Method.
in the stock, the percentage of carbon black below the 5-µm
9.3 In comparing a series of different compounds, it is also
size is calculated and expressed as “Percentage of Carbon
desirable to rate the specimens side by side rather than one at
Black Dispersed.”
a time. This use of a control compound is also advisable. This
is best prepared by individual operators, since dispersion
14. Significance and Use
requirements may vary greatly for different types of com-
14.1 Certain important physical properties of the compound
pounds. The control sample should represent a minimum
are influenced significantly by the degree of carbon black
acceptable dispersion level for the type of compound being
dispersion within the compound (for example, tensile strength
rated. Because it can be observed side by side with unknown
and abrasion resistance). The correlation of these properties
samples under identical conditions, a control compound is
with the percentage dispersion determined by theAgglomerate
more accurate than the photographic standards in discerning
Count Method approximates the following pattern for many
small deviations from what is considered the norm for a
types of black loaded rubber compounds:
specific type of compound. Prepare a fresh surface on the
Dispersion, % Classification
control as often as necessary to ensure cleanliness.
Above 99 Very high
10. Report
97 to 99 High
95 to 97 Intermediate
10.1 Ratings:
92 to 95 Low
10.1.1 List all ratings, including those on any control
Below 92 Very low
compound, on the basis of the 1 to 5 scale defined by the
15. Apparatus
standard photographs. Use fractional ratings when necessary.
10.1.2 Average the ratings on different specimens of the 15.1 Microtome—A sledge-type microtome equipped with
same compound as well as the ratings of different operators. specimen clamp and holder for glass knives. Steel knives may
Report the final average values. also be employed, according to the preference of the operator.
10.2 Compound Identification: 15.2 Freezing Blocks, consisting of a brass screw which is
10.2.1 Formulation—Wheneverpossiblelistthefollowing: threadedintoaninsulatingblockofTFE-fluorocarbon(Fig.2).
10.2.1.1 Carbon black, type and loading, The TFE-fluorocarbon block shall be 28-mm square in cross
D2663–95a (2000)
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—Forrubbersofhighunsat-
uration (for example, OE-SBR, NR, and BR), dust small bits
(enoughsubsequentlytoformbuttonsabout10mmindiameter
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
FIG. 2 Brass Sample Mount and TFE-Fluorocarbon Insulator about 10 to 15-min cure. After cure, scrape off the excess
peroxide from the sample surface and proceed with sectioning
inthestandardmanner,takingcarenottoparedownbelowthe
cured surface layer.
section and 40-mm high. The threaded part of the brass screw
17.2.1 For IIR, satisfactory surface cures can be obtained
shall be 15 mm in diameter and shall extend into the center of
with a mixture of 1 part tetramethylthiuram disulfide (TMTD),
the TFE-fluorocarbon block to a depth of 34 mm. Coarse,
1partmercaptobenzothiazole(MBT),1partsulfur,and5parts
expansion-type threads should be used to prevent splitting of
zinc oxide, with a cure of 1 h at 155°C. Other alternative
the TFE-fluorocarbon when the mount is frozen. The head of
approaches for curing high unsaturation polymers without
the brass screw shall be 18 mm in diameter and shall extend 3
actually mixing in curatives are (1) high-energy radiation and
mm above the TFE-fluorocarbon insulator. The top of the
(2) chemical treatment with sulfur monochloride. However,
screw head shall be cross-hatched with fine grooves to a depth
before using either of these latter methods, the stock should be
of about 1 mm.
pressed out to eliminate most of the air holes. Cure in
15.3 Microscope—An optical microscope with binocular
accordance with Practice D3182.
viewing (trinocular type if photomicrographs are desired) is
recommended. This should include a movable specimen stage
18. Test Specimen
and white light source with variable intensity. Lenses should
18.1 Cut out a rectangular specimen 8-mm long, 3-mm
include two 103 wide field eyepieces and objectives in the
wide, and approximately 2-mm deep. Use a cutting die, if
range from 6 to 103. Taking into account microscope tube
available. If a die is not used, the specimen length and width
corrections, objectives should be selected so that magnifica-
should be recorded using a measuring magnifier.
tions in the range from 75 to 1003 are available. (For
18.2 Prepare one specimen block for each different com-
photomicrographsa43planeobjectiveanda103periplanatic
pound to be examined.
eyepiece are recommended.)
15.4 Microscope Accessories—A 103 wide field eyepiece
19. Preparation of Glass Knives
containing a graticule that is 1 cm in size and divided into
19.1 Standard types of plate glass are suitable for making
10000 small squares.
knives. Thickness should be preferably about 6 mm. A large
15.5 Measuring Lens—A73 measuring magnifier cali-
sheet of glass should first be repeatedly broken in half so that
brateddownto0.1mmformeasuringtheswellingfactorofthe
it eventually is in 50-mm wide strips. Fracture in this manner
microtome sections. A mechanical vernier stage can also be
is preferred over simply breaking off 50-mm sections one at a
used for this purpose.
time. Uneven strains are encountered in the latter procedure,
15.6 Glass Pliers and Cutter—Wide-face glazier pliers and
and irregularities may occur on the side faces on which the
a wheel-type glass cutter are recommended for preparing glass
knifeedgewillbeformed.Priortofracture,itisalsoimportant
knives.
that the glass be free of dirt. A wash in a liquid detergent is
15.7 Sample Die—Tempered steel die for cutting out 3 by
generally advisable.
8-mm specimens.
19.2 Using a fairly thick straightedge, score a straight line
15.8 Sable Brushes (00).
(perpendicular to the side faces) across the glass strip, 50 mm
15.9 Dewar Flask, 2dm (2-L) size (wide-mouth).
from the end. Take care that the score mark does not actually
15.10 Glass Knives—Theknivesarepreparedfrom50-mm
extend all the way to the side faces or chipping may result.
wide strips of approximately 6-mm thick plate glass.
Next, fracture along the score line using the glass pliers. The
15.11 Microscope Slides and Cover Glass
...
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