ASTM D3493-21

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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: D3493 − 20 D3493 − 21
Standard Test Method for
Carbon Black—Oil Absorption Number of Compressed
Sample (COAN)
This standard is issued under the fixed designation D3493; 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 This test method covers the procedure for the mechanical compression of a carbon black sample and the determination of the
oil absorption number of the compressed sample.
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, 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.
2. Referenced Documents
2.1 ASTM Standards:
D1765 Classification System for Carbon Blacks Used in Rubber Products
D1799 Practice for Carbon Black—Sampling Packaged Shipments
D1900 Practice for Carbon Black—Sampling Bulk Shipments
D2414 Test Method for Carbon Black—Oil Absorption Number (OAN)
D4821 Guide for Carbon Black—Validation of Test Method Precision and Bias
D4483 Practice for Evaluating Precision for Test Method Standards in the Rubber and Carbon Black Manufacturing Industries
3. Summary of Test Method
3.1 A sample of carbon black is compressed four times in a compression cylinder at a pressure of 165 MPa (24 000 psi) and then
tested in an absorptometer to determine the oil absorption number.
3.2 n-Dibutyl phthalate, paraffin oil, or EFA oil is added by means of a constant-rate buret to the compressed sample of carbon
black in the mixer chamber of an absorptometer. As the sample absorbs the oil, the mixture changes from a free-flowing state to
one of a semiplastic agglomeration, with an accompanying increase in viscosity. This increased viscosity is transmitted to the
torque-sensing system of the absorptometer. When the viscosity of the mixture reaches a predetermined torque level, the
This test method is under the jurisdiction of ASTM Committee D24 on Carbon Black and is the direct responsibility of Subcommittee D24.11 on Carbon Black Structure.
Current edition approved Dec. 1, 2020June 1, 2021. Published January 2021July 2021. Originally approved in 1976. Last previous edition approved in 20192020 as
D3493 – 19a.D3493 – 20. DOI: 10.1520/D3493-20.10.1520/D3493-21.
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.
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D3493 − 21
absorptometer and buret will simultaneously shut off. The volume of oil added is read from the direct reading buret. The volume
of oil per unit mass of carbon black is the oil absorption number. Either DBP, paraffin oil, or EFA oil is acceptable for use with
many standard pelleted grades of N-series carbon blacks found in Classification D1765. COAN testing using paraffin oil or EFA
oil on some specialty blacks and powder blacks may result in significant differences when compared to COAN testing using DBP
oil. Referee testing between suppliers and users should use DBP oil until such time that precision data is available for paraffin and
EFA oils.
4. Significance and Use
4.1 The oil absorption number of a carbon black is related to the processing and vulcanizate properties of rubber compounds
containing the carbon black.
4.2 The difference between the regular oil absorption number and the oil absorption number of compressed sample is some
measure of the stability of the structure of the carbon black.
5. Apparatus
5.1 Balance, analytical, 0.01-g sensitivity.
5.2 Oven, gravity-convection type, capable of maintaining 125°C 6 5°C.
5.3 Carbon Black Press, capable of compressing a 25-g sample to 165 MPa (24 000 psi).
3 3
5.4 Absorptometer, equipped with a constant-rate buret that delivers 67 6 0.4 mm /s (4 6 0.024 cm /min).
5.5 Spatula, rubber, 100 mm.
5.6 Tablespoon, stainless steel.
5.7 Sieve, 850 μm (U.S. No. 20), approximately 125-mm (5-in.) diameter with receiver pan.
5.8 Brush, approximately 40 mm (1.5 in.), stiff bristle.
5.9 Desiccator.
6. Reagent and Standards
6.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where
such specifications are available. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
6.2 n-Dibutyl Phthalate, having a density of 1.042 to 1.047 mg ⁄m at 25°C and a relative density of 1.045 to 1.050 at 25°C.
2 5
6.3 Paraffın Oil, having a kinematic viscosity of 10 to 34 mm /s (cSt) at 40°C.
6.4 Epoxidized Fatty Acid Ester (EFA), meeting the specifications listed in Test Method D2414, Table 1. It is recommended to store
Each apparatus is to be operated and maintained in accordance with the manufacturer’s directions for optimum performance.
Reagent Chemicals, American Chemical Society Specifications , American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
The sole source of supply of paraffin oil (Marcol 82, which has been demonstrated to provide comparable results to DBP oil) known to the committee at this time is
Exxon. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at
a meeting of the responsible technical committee, which you may attend.
D3493 − 21
the product at temperatures between 7 and 30°C. If stored in sealed original containers, the product is stable for at least 12 months.
For handling and safety, please refer to safety data sheet.
6.5 ASTM D24 Standard Reference Blacks, SRB.
7. Sampling
7.1 Samples shall be taken in accordance with Practices D1799 and D1900.
8. Calibration and Standardization
8.1 See Test Method D2414.
NOTE 1—If values are not obtained within the acceptable range, it will be necessary to either vary the pressure of the hydraulic press until acceptable
values are obtained or follow Guide D4821.
9. Procedure
9.1 Dry an adequate sample for 1 h in a specified oven set at 125°C. Cool the sample in a desiccator for a minimum of 30 min
prior to testing.
9.2 Weigh a sample mass of either 25, 30, or 45 g depending on the sample mass requirement for oil absorption per Test Method
D2414. The desired sample mass to be compressed will weigh 5 6 0.1 g greater than the mass specified in subsection 10.2 of Test
Method D2414.
9.3 Compress the sample using a carbon black press per the manufacturer instructions.
9.4 A general procedure for compressing carbon black involves the following steps:
9.4.1 Ensure the cylinder and piston tips are clean.
9.4.2 Open the press by moving the pistons is a proper position to add carbon black.
9.4.3 Add the desired amount of carbon black to the cylinder using a funnel.
9.4.4 Compress the carbon black to approximately 165 MPa (24 000 psi), hold for about 1 s, then release.
9.4.5 Open the press to release the carbon black in t
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