ASTM D2663-95a(2006)
(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: SectionsTest Method A-Visual InspectionTest Method B-Agglomerate CountTest Method C-Microroughness Measurement
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 2006)
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 Carbon Black Dispersion Standards
Carbon Black Dispersion Chart
1.1 These test methods determine the degree of dispersion
of carbon black in rubber. Three test methods are described as
TEST METHOD A—VISUAL INSPECTION
follows:
Sections 3. Scope
Test Method A—Visual Inspection 3-11
3.1 Test Method A is a qualitative visual test method.
Test Method B—Agglomerate Count 12-23
Test Method C—Microroughness Measurement 24-34 Ratings are made against a set of standard photographs (Fig.
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.
1.3 This standard does not purport to address all of the
4. Summary of Test Method
safety concerns, if any, associated with its use. It is the
4.1 The compound rubber is torn or cut to expose a fresh
responsibility of the user of this standard to establish appro-
surface for examination by the eye, aided preferably by a hand
priate safety and health practices and determine the applica-
lens or a low-power binocular microscope. The dispersion
bility of regulatory limitations prior to use.
level of the carbon black is compared against a series of five
2. Referenced Documents photographic standards and then rated numerically from 1
2 (very low) to 5 (high) (see Fig. 1).
2.1 ASTM Standards:
D1765 Classification System for Carbon Blacks Used in
5. Significance and Use
Rubber Products
5.1 Visual dispersion ratings correlate with certain impor-
D3051 Recommended Practice for Carbon Black—Stating
tant physical properties of the compound. A rating of 5
the Precision of ASTM Test Methods
indicates a state of dispersion developing near maximum
D3182 Practice for Rubber—Materials, Equipment, and
properties, while a rating of 1 would indicate a state of
Procedures for Mixing Standard Compounds and Prepar-
dispersion developing considerably depressed properties. Nor-
ing Standard Vulcanized Sheets
mally, the visual dispersion ratings indicate the following
D 3396 Recommended Practice for Carbon Black—
3 levels of compound quality:
Measuring the Precision of ASTM Test Methods
Visual Dispersion Rating Classification
D4483 Practice for Evaluating Precision for Test Method
Standards in the Rubber and Carbon Black Manufacturing
4to5 High
Industries 3 to 4 Intermediate
2to3 Low
2.2 ASTM Adjuncts:
1 to 2 Very low
6. Apparatus
6.1 Sharp Knife or Razor Blade.
6.2 Hand Lens (103)orbinocularmicroscope(10to203).
These test methods are under the jurisdiction of ASTM Committee D24 on
6.3 Illuminator, microscopical-type.
Carbon Black and are the direct responsibility of Subcommittee D24.71 on Carbon
Black Testing in Rubber. 6.4 Knife Heater.
Current edition approved July 15, 2006. Published August 2006. Originally
e1
approvedin1967.Lastpreviouseditionapprovedin2000asD2663–95a(2000) .
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 Available from ASTM International Headquarters. Order Adjunct No.
Standards volume information, refer to the standard’s Document Summary page on ADJD266302. Original adjunct produced in 1967.
the ASTM website. Available from ASTM International Headquarters. Order Adjunct No.
Withdrawn. ADJD266301. Original adjunct produced in 1967.
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D2663–95a (2006)
FIG. 1 Carbon Black Dispersion Standards—Visual Analysis of Torn Vulcanizates
6.5 Series of Photographic Standards, rating 1 to 5. These 7. Test Specimen
standards give the following percent dispersion ratings by the
7.1 Vulcanized Compounds—Use a slab of rubber about
Agglomerate Count Method:
2mm in thickness. Tear it so that a fresh surface is exposed.
Visual Rating Black Dispersed, %
The tear may be initiated by a small cut. The most nearly flat
280 part of the tear is used for rating.
7.2 Unvulcanized Compounds—Unvulcanized rubber may
be examined as follows:
D2663–95a (2006)
7.2.1 Ifthespecimencontainscuringagents,sheetitoutand specific type of compound. Prepare a fresh surface on the
cure in a press to form a vulcanized slab about 2 mm in control as often as necessary to ensure cleanliness.
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-
priate materials with a minimum of mixing. Then cure and 10.1.1 List all ratings, including those on any control
compound, on the basis of the 1 to 5 scale defined by the
proceed as above.
7.2.3 If the specimen contains no curatives and a dispersion standard photographs. Use fractional ratings when necessary.
10.1.2 Average the ratings on different specimens of the
evaluation with no further mixing is required, the compound
must first be compressed to remove most of the air holes. To same compound as well as the ratings of different operators.
Report the final average values.
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 10.2 Compound Identification:
10.2.1 Formulation—Whenever possible list the following:
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 10.2.1.1 Carbon black, type and loading,
10.2.1.2 Other fillers, type and loading,
smooth cutting stroke using a sharp, hot knife (a standard type
knife heater may be employed). The most nearly smooth and 10.2.1.3 Polymer type, and
10.2.1.4 Extender oil, type and loading.
flat part of the cut surface is used for rating.
10.2.2 Mixing—Describe the mixing of the compound in
terms of one or more of the following:
8. Number of Tests
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
12. Scope
matched numerical rating to each compound being rated. In
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-
13. Summary of Test Method
quency, the surface of stocks of this type may show a general
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
14. Significance and Use
is best prepared by individual operators, since dispersion
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:
D2663–95a (2006)
15.7 Sample Die—Tempered steel die for cutting out 3 by
Dispersion, % Classification
8-mm specimens.
Above 99 Very high
15.8 Sable Brushes (00).
97 to 99 High
15.9 Dewar Flask, 2dm (2-L) size (wide-mouth).
95 to 97 Intermediate
92 to 95 Low
15.10 Glass Knives—The knives are prepared from 50-mm
Below 92 Very low
wide strips of approximately 6-mm thick plate glass.
15.11 Microscope Slides and Cover Glasses.
15. Apparatus
15.1 Microtome—A sledge-type microtome equipped with
16. Reagents and Materials
specimen clamp and holder for glass knives. Steel knives may
16.1 Liquid Nitrogen.
also be employed, according to the preference of the operator.
16.2 Water-Soluble Mucilage.
15.2 Freezing Blocks, consisting of a brass screw which is
16.3 Naphtha,boilingpointrangefromabout113to144°C.
threadedintoaninsulatingblockofTFE-fluorocarbon(Fig.2).
16.4 Xylene, boiling point range from 135 to 145°C.
The TFE-fluorocarbon block shall be 28-mm square in cross
section and 40-mm high. The threaded part of the brass screw
17. Sampling
shall be 15 mm in diameter and shall extend into the center of
17.1 Vulcanizates—Specimens may be cut from standard
the TFE-fluorocarbon block to a depth of 34 mm. Coarse,
test sheets (about 2-mm thick) or from pieces of actual cured
expansion-type threads should be used to prevent splitting of
articles. Vulcanized samples must be employed because of the
the TFE-fluorocarbon when the mount is frozen. The head of
solvent used to uncurl the thin sections. If pieces other than
the brass screw shall be 18 mm in diameter and shall extend
2-mm sheets are used, they should first be cut down to a
3mm above the TFE-fluorocarbon insulator. The top of the
thickness of about 2 to 3 mm.
screw head shall be cross-hatched with fine grooves to a depth
17.2 Unvulcanized Compounds—Forrubbersofhighunsat-
of about 1 mm.
uration (for example, OE-SBR, NR, and BR), dust small bits
15.3 Microscope—An optical microscope with binocular
(enoughsubsequentlytoformbuttonsabout10mmindiameter
viewing (trinocular type if photomicrographs are desired) is
and about 2 to 3-mm deep) thoroughly with dicumyl peroxide.
recommended. This should include a movable specimen stage
Cure in a button mold under high pressure at about 155°C.
and white light source with variable intensity. Lenses should
OE-SBR rubbers require about 30 to 60-min cure. BR requires
include two 103 wide field eyepieces and objectives in the
about 10 to 15-min cure. After cure, scrape off the excess
range from 6 to 103. Taking into account microscope tube
peroxide from the sample surface and proceed with sectioning
corrections, objectives should be selected so that magnifica-
inthestandardmanner,takingcarenottoparedownbelowthe
tions in the range from 75 to 1003 are available. (For
cured surface layer.
photomicrographsa43planeobjectiveanda103periplanatic
17.2.1 For IIR, satisfactory surface cures can be obtained
eyepiece are recommended.)
with a mixture of 1 part tetramethylthiuram disulfide (TMTD),
15.4 Microscope Accessories—A 103 wide field eyepiece
1partmercaptobenzothiazole(MBT),1partsulfur,and5parts
containing a graticule that is 1 cm in size and divided into
zinc oxide, with a cure of 1 h at 155°C. Other alternative
10000 small squares.
approaches for curing high unsaturation polymers without
15.5 Measuring Lens—A 73 measuring magnifier cali-
actually mixing in curatives are (1) high-energy radiation and
brateddownto0.1mmformeasuringtheswellingfactorofthe
(2) chemical treatment with sulfur monochloride. However,
microtome sections. A mechanical vernier stage can also be
before using either of these latter methods, the stock should be
used for this purpose.
pressed out to eliminate most of the air holes. Cure in
15.6 Glass Pliers and Cutter—Wide-face glazier pliers and
accordance with Practice D3182.
a wheel-type glass cutter are recommended for preparing glass
knives.
18. Test Specimen
18.1 Cut out a rectangular specimen 8-mm long, 3-mm
wide, and approximately 2-mm deep. Use a cutting die, if
available. If a die is not used, the specimen length and width
should be recorded using a measuring magnifier.
18.2 Prepare one specimen block for each different com-
pound to be examined.
19. Preparation of Glass Knives
19.1 Standard types of plate glass are suitable for making
knives. Thickness should be preferably about 6 mm. A large
sheet of glass should first be repeatedly broken in half so that
it eventually is in 50-mm wide s
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