ASTM D3765-99
(Test Method)Standard Test Method for Carbon Black-CTAB (Cetyltrimethylammonium Bromide) Surface Area
Standard Test Method for Carbon Black-CTAB (Cetyltrimethylammonium Bromide) Surface Area
SCOPE
1.1 This test method covers the measurement of the specific surface area of carbon black exclusive of area contained in micropores too small to admit hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide, commonly referred to as CTAB) molecules. This test method is suitable for characterizing rubber-grade carbon blacks of all types.
1.2 The values stated in SI units are to be regarded as the standard. The values given 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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Standards Content (Sample)
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Designation: D 3765 – 99
Standard Test Method for
Carbon Black—CTAB (Cetyltrimethylammonium Bromide)
Surface Area
This standard is issued under the fixed designation D 3765; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope ultrasonic vibration. Titration with dioctyl sodium sulfosucci-
nate (Aerosol OT ) solution to a turbidity maximum end point
1.1 This test method covers the measurement of the specific
is used to determine the unadsorbed CTAB after removal of the
surface area of carbon black exclusive of area contained in
colloidally dispersed carbon black by ultrafiltration. All results
micropores too small to admit hexadecyltrimethylammonium
are scaled by using the Industry Tint Reference Black (ITRB)
bromide (cetyltrimethylammonium bromide, commonly re-
as a primary standard and taking its accessible surface area to
ferred to as CTAB) molecules. This test method is suitable for
3 2
be exactly 83.0 3 10 m /kg.
characterizing rubber-grade carbon blacks of all types.
3.2 Titration of the unadsorbed CTAB with Aerosol OT
1.2 The values stated in SI units are to be regarded as the
solution is accomplished by the following:
standard. The values given in parentheses are for information
3.2.1 Part A—Automatic Titration.
only.
3.2.2 Part B—Manual Turbidity Titration.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 The CTAB molecule is relatively large; so it is not
priate safety and health practices and determine the applica-
adsorbed in micropores or on surface roughness. Thus, the
bility of regulatory limitations prior to use.
CTAB surface area reflects only the surface of the carbon black
2. Referenced Documents that is available for interaction with rubber molecules.
2.1 ASTM Standards:
5. Apparatus
D 1193 Specification for Reagent Water
5.1 Analytical Balance, 0.1-mg sensitivity.
D 1799 Practice for Carbon Black—Sampling Packaged
5.2 Ultrasonic Cleaning Bath, modified to incorporate
Shipments
integral magnetic stirring and vial holder to properly position
D 1900 Practice for Carbon Black—Sampling Bulk Ship-
two sample vials. (If desired, a separate ultrasonic cleaning
ments
6 7
bath and a separate magnetic stirrer may be used.)
D 4483 Practice for Determining Precision for Test Method
5.3 Magnetic Spinbars, chemically resistant covered (poly-
Standards in the Rubber and Carbon Black Industries
chlorotrifluoroethylene or TFE-fluorocarbon), 6.4 or 4.8-mm
1 3
3. Summary of Test Method ( ⁄4 or ⁄16-in.) diameter, and length nearly equal to the diameter
of 50 or 100-cm Berzelius beakers, glass vials, or other glass
3.1 The isotherm for adsorption of an aqueous solution of
vessels.
CTAB on carbon black has a long horizontal plateau corre-
sponding to a monolayer coverage of the substrate surface from
which the adsorbate is not sterically excluded. The CTAB
adsorption by carbon black is independent of residual tars and
functional groups containing hydrogen and oxygen, etc. Rapid
equilibration is achieved by using mechanical stirring and
Aerosol OT is a registered trademark of the American Cyanamid Co., Process
Chemicals Dept., Wayne, NM 07470.
1 5
This test method is under the jurisdiction of ASTM Committee D-24 on Carbon Available from L.A. King Manufacturing Corp., LAKO Division, P.O. Box
Black and is the direct responsibility of Subcommittee D24.21 on Adsorptive 2415, Tulsa, OK 74101.
Properties of Carbon Black. Millipore Corp., Bedford, MA 01730, Catalog No. XX 66 00900 is satisfactory.
Current edition approved August 10, 1999. Published September 1999. Origi- Sargent magnetic stirrer S-76490 is satisfactory.
nally published as D 3765 – 79. Last previous edition D 3765 – 98. Examples of suitable spinbars are Catalog No. 9235-U7, A. H. Thomas Co.,
Annual Book of ASTM Standards, Vol 11.01. Philadelphia, PA 19105, or Catalog No. S-76497-30, Sargent Welch Scientific Co.,
Annual Book of ASTM Standards, Vol 09.01. Skokie, IL 60076.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3765
5.4 Microfiltration Membrane Filter Disks, 47-mm diam- 5.16 Gravity Convection Drying Oven, capable of maintain-
eter. ing 125 6 5°C.
5.5 Filter Holder. 5.17 Microscope Spotlight.
5.6 Sampling Cylinder, 30-cm stainless steel, double end 5.18 TFE-fluorocarbon Pipe Thread Sealing Tape.
with 6.4-mm ( ⁄4-in.) NPT female openings, suitable for 0.7- 5.19 Magnetic Stirrer.
MPa (100-psi) pressure. 5.20 Containers, suitable for preparation and storage of
5.7 Pressure Manifold, connected to air or nitrogen supply reagent solutions.
regulated at 0.4 to 0.7 MPa (60 to 100 psi). Fig. 1 shows a 5.21 Automatic Titration Equipment, with instruction
schematic diagram of a typical assembly. manual.
5.8 Glass Funnel, small. 5.22 Beakers, 100-cm Berzelius, tall form, (one furnished
5.9 Glass Vials, with plastic screw caps, 28 mm in outside with automatic titration equipment).
diameter, about 40-cm capacity (11-dram size). 5.23 Thermometer, to measure temperature in a range from
3 3
5.10 Buret, 50-cm , 0.1-cm divisions, Class A, preferably 20 to 40°C.
of automatic refilling and zeroing type (Note 1) with reagent 5.24 Polyethylene Tubing (do not use vinyl tubing).
reservoir.
NOTE 2—All apparatus must be kept chemically clean. Contamination
of equipment, water supply, or chemicals by ionic surfactants must be
NOTE 1—Automatic burets are usually not certified to Class A toler-
particularly avoided. The filtration equipment, especially the region below
ance. Such burets should be checked for accuracy, and, if in error by more
the perforated plate in the filter holder, must not be permitted to
than 0.05 cm at any point, a calibration curve should be prepared and
accumulate carbon black or cleanser residues.
used to correct observed buret readings. Burets with TFE-fluorocarbon
manostat valves offer some advantage in ease of stopcock manipulation in
6. Reagents
delivering small increments of titrant.
12 6.1 Purity of Reagents—Reagent grade chemicals shall be
5.11 Dispenser-Type Pipet, 50-cm , attached to a suitable
used in all tests. Unless otherwise indicated, it is intended that
reservoir for CTAB solution.
all reagents conform to the specifications of the Committee on
5.12 Pipet, 10-cm , Class A.
Analytical Reagents of the American Chemical Society where
5.13 Erlenmeyer Flasks, or beakers, 50 or 100-cm .
such specifications are available. Other grades may be used,
5.14 Dropping Bottle, 60-cm amber.
5.15 Jar, wide-mouth, plastic screw cap, 118 or 236-cm (4
or 8-oz) size.
This test is based on the use of three sources of automatic titration equipment:
(1) Mettler Memotitrator DL40RC, Mettler Instrument Co., Box 71, Highstown, NJ
08520, (2) Brinkman Dosimat 665 Buret, Brinkman Instruments, Inc., Cantiague
Rd., Westbury, NY, and (3) ATMAST, available from L. A. King Manufacturing
This test is based on the use of three brands of microfiltration membrane: (1)
Corp., LAKO Division, P.O. Box 2415, Tulsa, OK 74101. The Probe Colorimeter,
Gelman HT-200, Gelman No. 66199, Baxter Scientific Cat. No. F2988-2, Baxter
also available from Brinkman Instruments, has been found to be an acceptable
Scientific Products, 1430 Waukegan Rd., McGraw Park, IL 60085; (2) Microfiltra-
automatic means of detecting the titration end point. This piece of equipment may
tion Systems, Cat. No. A-010A047A, 6800 Sierra Court, Dublin, CA 94566; and (3)
be integrated with the Brinkman Dosimat 665 Buret.
Millipore Cat. No. SAIJ076H7 Filters, Millipore Corp., Bedford, MA 01730.
“Reagent Chemicals, American Chemical Society Specifications,” Am.
This test is based on the use of Swinnex-47 filter holders obtained from
Chemical Soc., Washington, DC. For suggestions on the testing of reagents not
Millipore Corp. as Catalog No. SX00 047 00.
11 listed by the American Chemical Society, see “Reagent Chemicals and Standards,”
Hoke, Inc., Kresskill, NJ 07626, No. 4DY30 is suitable.
12 by Joseph Rosin, D. Van Nostrand Co., Inc., New York, NY, and the “United States
This test is based on the use of the Universal Repipet, a registered trademark
Pharmacopeia.”
of Labindustries, 1802 Second St., Berkeley, CA 94710.
FIG. 1 Pressure Filtration Manifold
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 3765
provided it is first ascertained that the reagent is of sufficiently 8.2 Weigh, to 0.1 mg, five samples of the dried ITRB
high purity to permit its use without lessening the accuracy of covering the range from 0.2 to 0.6 g in intervals of about 0.1 g.
the determination. 8.3 With each sample, carry out the equilibration and
6.2 Purity of Water— Unless otherwise indicated, refer- filtration in accordance with 9.3-9.8 and the titration in
ences to water shall be understood to mean reagent water as accordance with 9.9.1 or 9.9.2.
defined by Type 1 in Specification D 1193. 8.4 Plot the titration volumes, V, against the sample masses,
6.3 Buffer Solution of pH 7 (0.05M)—Prepare buffer solu- W. Fit the best possible straight line through the points
tion by dissolving 2.722 g of monobasic potassium phosphate (preferably by least squares regression) and determine the
(KH PO ), 4.260 g of dibasic sodium phosphate (Na HPO ) slope, b, (cubic centimetres per gram) and the volume axis
2 4 2 4
and 1.169 g of sodium chloride (NaCl) in 1 dm of distilled intercept, V .
o
water. Alternatively, this prepared solution may be pur- 8.5 The factors V and b are the standardization factors used
o
chased. in the calculation of CTAB surface area. Standardization is
6.4 CTAB Standard Solution (0.0100 M)—Dissolve 3.64 g necessary each time the CTAB or Aerosol OT solution is
of reagent-grade CTAB per 900 cm of distilled or deionized prepared.
water. Add 100 cm of the 7.0 pH buffer solution to this 8.6 From these numbers, the CTAB surface area (SA)ofan
solution. Warm the solution to a temperature of 27 to 37°C to unknown black tested with these reagents can be obtained from
facilitate the solution. Cool to a temperature between 22 and the following equation:
25°C before using.
SA ~V 2 V!
ITRB o
SA 5 3 (1)
2b W
NOTE 3—Caution: Storage of the solution below 22°C will result in
slow crystallization of the CTAB.
where:
4 ,18
3 2
6.5 Aerosol OT Solution 100 % Grade (approximately
SA 5 CTAB surface area, 10 m /kg,
0.0022 M)—Dissolve 1.000 g/dm of Aerosol OT solution
V 5 intercept from the standardization plot,
o
(100 % solids) in distilled or deionized water containing 2.5 cm
b 5 slope from the standardization plot,
3/dm of 37 % formaldehyde, by swirling vigorously with a
V 5 volume of Aerosol OT solution,
W 5 mass of unknown black, and
magnetic stirrer for 48 h. Allow to stand an additional twelve
3 2
SA 5 83.0 3 10 m /kg.
days before standardization and use. (Aerosol OT solution may
ITRB
8.7 The five data points from the standardization should be
be subject to slow biodegradation in the absence of formalde-
inserted into this formula to check the reliability of the
hyde.) The solution should be capped tightly and stored in a
3 2
standardization. CTAB SA of 83.0 6 1 3 10 m /kg for ITRB
cool place. (Once opened, 100 % Aerosol OT should be stored
should be obtained. If all five data points or daily calibration
in a desiccator.)
checks do not agree with assigned values, repeat the standard-
6.6 Formaldehyde Solution, approximately 37 %.
19 3 2
ization, paying special emphasis to equipment and equilibra-
6.7 ITRB, equals 83.0 3 10 m /kg surface area.
tion in 9.3 and 9.4.
6.8 Bromophenol Blue, reagent grade.
6.9 Ethanol, reagent grade.
9. Procedure
6.10 Distilled or Deionized Water.
9.1 Dry an adequate sample of carbon black at 125°C for 1
6.11 Octylphenoxy Polyethoxyethanol (Triton X-100 ) So-
h and cool in a desiccator.
lution (0.15 %)— Dissolve 1.5 g/dm of Triton X-100 (100 %
liquid) in distilled or deionized water by swirling vigorously
NOTE 4—If the heating loss of the carbon black is known, the drying
with a magnetic stirrer until a homogeneous solution is
step may be omitted and the observed sample mass corrected for heating
obtained. loss to obtain the mass of dry sample, W.
9.2 Weigh, to 0.1 mg, a suitable sample of the dried carbon
7. Sampling
black into a glass vial and record the mass as W. Appropriate
7.1 Samples shall be taken in accordance with Practice
sample masses may be selected as follows:
D 1799 or D 1900.
Grade of Black CTAB Range, m /kg Sample Mass, g
N100 Series 125 to 150 3 10 0.30
8. Standardization of Reagents N200 100 to 130 3 10 0.35
N300 75 to 105 3 10 0.40
8.1 Dry an adequate portion of ITRB for1hat125 6 1°C.
N351-N440 50 to 75 3 10 0.60
N500-N600 35 to 50 3 10 0.90
N700 25 to 30 3 10 1.35
An appropriate sample mass may also be taken as V /S in
Bates, R. G., Hamer, W. J., Manor, G. G., and Acree, S. F., Journal of
o est
Research, National Institute of Standards and Technology, No. 29, 1942, p. 183.
grams, where S is some estimate of the expected CTAB
est
Available from Fisher Scientific Co., Catalog No. SB-108, 711 Forbes Ave.,
surface area.
Pittsburgh, PA 19105.
17 9.3 Insert a magnetic spinbar into the vial. Add 30.0 cm of
Available from J. T. Baker Chemical Co., 222 Red School Lane, Phillipsburgh,
CTAB solution from the dispensing pipet or buret taking care
NJ 08865, Catalog No. 7N121.
Available from American Cyanamid Co., Process Chemicals Dept., Wayne,
to prevent foaming of the solution. Cap the vial.
NM 07470. Also available as Catalog No. A-349 from Fisher Scientific Co.
9.4 Insert the vial into the ultrasonic bath that contains water
Available from Ashland Chemical Co., Carbon Black Division, P.O. Box 2219,
at a temperature between 22 and 25°C to a depth of at least 50
Columbus, OH 43216.
Triton X-100 is a registered trademark of Rohm and Haas Co. mm (2 in.). Adjust the magnetic stirrer to give vigorous stirring
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) f
...
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