ASTM D4661-23

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Designation: D4661 − 18 D4661 − 23
Standard Test Methods for
Polyurethane Raw Materials: Determination of Total Chlorine
in Isocyanates
This standard is issued under the fixed designation D4661; 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 determine the total chlorine content of aromatic isocyanates used as polyurethane raw materials. The
difference between the total chlorine content and the hydrolyzable chlorine content (see Test Method D4663) is a measure of the
amount of chlorobenzene, o-dichlorobenzene-dichlorobenzene, and other ring-substituted chlorinated products that are present.
Both procedures are applicable to a variety of organic compounds but the amount of sample used may have to be is varied. (See
Note 1.)
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.
NOTE 1—This standard is identical to ISO 26603.
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:
D883 Terminology Relating to Plastics
D1193 Specification for Reagent Water
D4663 Test Method for Polyurethane Raw Materials: Determination of Hydrolyzable Chlorine of Isocyanates
2.2 ISO Standard:
ISO 26603 Plastics—Aromatic isocyanates for use in the production of polyurethanes—Determination of total chlorine
3. Terminology
3.1 Definitions—For definitions of terms used in these test methods see Terminology D883.
These test methods are under the jurisdiction of ASTM Committee D20 on Plastics and are the direct responsibility of Subcommittee D20.22 on Cellular Materials -
Plastics and Elastomers.
Current edition approved Aug. 1, 2018March 1, 2023. Published August 2018March 2023. Originally approved in 1987. Last previous edition approved in 20132018 as
D4661 - 13.D4661 - 18. DOI: 10.1520/D4661-18.10.1520/D4661-23.
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 American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard
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D4661 − 23
4. Summary of Test Method
4.1 In each test method, the organic matter in the sample is destroyed by combustion with oxygen, the organically combined
chlorine being converted to ionic chloride. The chloride is determined potentiometrically by titration with silver nitrate (AgNO )
solution.
4.1.1 Test Method A—The sample is combusted in a pressurized ignition vessel.
4.1.2 Test Method B—The sample is combusted at atmospheric pressure in a Schöniger oxygen flask.
5. Significance and Use
5.1 These test methods can be used are suitable for use for research or for quality control to determine the total chlorine content
of aromatic isocyanates. In some instances total chlorine content may correlate with performance in polyurethane systems.
6. Interferences
6.1 Bromine and iodine, if present, will react with the silver nitrate (AgNO ) solution leading to an erroneously high total chlorine
value.
7. Reagents and Materials
7.1 Purity of Reagents—Use reagent-grade chemicals in all tests. Unless otherwise indicated, it is intended that all reagents
conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such
specifications are available. Other grades are acceptable, provided it is first ascertained that the reagent is of sufficiently high
purity to permit its use without lessening the accuracy of the determination.
7.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by Type
I of Specification D1193.
8. Sampling
8.1 Since organic isocyanates react with atmospheric moisture, take special precautions in sampling. Usual sampling methods,
even when conducted rapidly, can cause contamination of the sample with insoluble urea. Therefore, blanket the sample with dry
air or nitrogen at all times. (Warning—Diisocyanates are eye, skin and respiratory irritants at concentrations above the
occupational exposure limit (TLV or PEL). Diisocyanates can cause skin and respiratory sensitization (asthma) in some people.
Once sensitized, it is essential to limit further exposure to diisocyanates. Use a combination of engineering controls and personal
protective equipment, including respiratory, skin and eye protection, to prevent over-exposure to diisocyanates. Consult the product
suppliers’ Safety Data Sheet (SDS) for more detailed information about potential health effects and other specific safety and
handling instructions for the product.)
9. Test Conditions
9.1 It is essential that moisture be excluded from the sample by all means possible to ensure the accuracy of measurements in this
standard. See Section 8 of this standard for guidance on how to keep moisture out of the sample.
TEST METHOD A—TOTAL CHLORINE BY OXYGEN IGNITION VESSEL
10. Apparatus
10.1 Weighing Bottle and Balance, suitable for weighing a liquid sample by difference to the nearest 0.5 milligram.
For information on the Schöniger flask, refer to Microchemie, Springer Publishers, Vienna, Austria, Vol 42, 1955, p. 123, or Vol 43, 1956, p. 869.
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. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.
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10.2 Oxygen Ignition Vessel Apparatus.
10.3 Fuse Wire, iron-nickel-chromium, No. 34 B & S gauge.
10.4 Potentiometric Titrator.
10.5 Silver-Silver Chloride Electrode.
10.6 Silver Electrode.
10.7 Bubble Counter, a 100-mL graduate and delivery tube or a bent “L” glass tube connected to a piece of rubber tubing. The
graduate is filled to the 50-mL mark with water to which 3 mL of 0.1 N AgNO solution and 1 drop of concentrated nitric acid
(HNO , sp gr 1.42) have been added. Any turbidity that develops indicates the HCl gas is being lost when venting the ignition
vessel.
10.8 Microburet, 10-mL capacity, 0.05-mL graduations.
11. Reagents
11.1 Ethyl Alcohol, conforming to Formula No. 2 B of the U.S. Treasury Department Bureau of Alcohol, Tobacco, and Firearms.
11.2 Nitric Acid—To 100 mL of water cooled in an ice bath, add 100 mL of nitric acid (HNO , sp gr 1.42) while stirring
vigorously.
11.3 Oxygen—Free of combustible materials and halogen compounds.
11.4 Silver Nitrate, Standard Solution (0.01 N)—Prepare a 0.01 N silver nitrate (AgNO ) solution, and standardize frequently
enough to detect changes of 0.0005 N, either gravimetrically or potentiometrically, using standard hydrochloric acid (HCl).
11.5 Sodium Carbonate Solution (50 g/L)—Dissolve 135 g of sodium carbonate decahydrate (Na CO · 10H O) in water and
2 3 2
dilute to 1 litre.liter.
12. Procedure
12.1 Make certain that the ignition vessel (Note 2), oxygen lines, and fittings are free of oil and grease. (Warning—Small
quantities of either may have been known to cause a violent explosion.)
NOTE 2—When the ignition vessel is used repeatedly, a film may form on its inner surface. Remove this film periodically by rotating the ignition vessel
on a lathe at about 300 rpm and polishing the inside surface with Grit No. 2/0 or equivalent paper coated with a light machine oil to prevent cutting and
then with a paste made from grit-free chromic oxide and water. This procedure will remove all but very deep pits while polishing the surface well. Before
using the ignition vessel, wash it with soap and water to remove residual cutting oil or paste. Ignition vessels with pitted surfaces are not to be used
because they will retain chlorine from sample to sample.
12.2 Weigh a 0.9-g sample by difference to 60.0005 g into the combustion capsule. (Warning—A severe safety hazard exists if
more than 1 g of sample is used.)
12.3 Fit a 100-mm, iron-nickel fuse wire onto the two electrodes. Place the combustion capsule on the loop electrode and adjust
the fuse wire in the capsule so that it is under the surface of the sample but does not touch the capsule. Place about 5 mL of Na CO
2 3
solution in the ignition vessel and, with a rubber policeman, wet the interior surface of the ignition vessel, including the head, as
These test methods as written are based on the use of Parr Bomb No. 1108 which has been found to be satisfactory for this purpose. The Parr Bomb No. 1108 is available
from the Fisher Scientific Co., 585 Alpha Dr., Pittsburgh, PA. Equivalent apparatus may be substituted with appropriate changes in the procedure.
Zero grade oxygen is suitable for this analysis. Any grade of oxygen that gives a suitable blank is to be used.
D4661 − 23
thoroughly as possible. Put the ignition vessel head in the vessel cylinder and the contact ring on top of the ignition vessel head,
screwing the cap down finger-tight. Close the outlet valve securely with the special wrench provided and open the main oxygen
cylinder slightly. Place the ignition vessel in its bench-mounted holder and tighten the holder bolt with an Allen wrench. Attach
the union on the oxygen-filling connection to the inlet valve of the ignition vessel. Admit oxygen slowly (to prevent blowing the
sample from the cup) to 20 to 25 atmospheres (2.03 to 2.53 MPa). Close the operating valve of the oxygen cylinder and observe
the pressure on the ignition vessel gauge. If a leak is indicated by a gradual pressure drop, check and tighten all connections. Do
not continue with the test until the leak is stopped and the ignition vessel holds pressure. Release the pressure from the oxygen
tank and disconnect the ignition vessel. Place the valve thumb nut on the oxygen inlet valve and tighten finger tight.
(Warning—Exercise extreme caution from this point on until the ignition vessel has been fired, cooled, and bled free of oxygen.)
12.4 Pull the plug to the ignition vessel ignition unit. Fill the ignition receptacle ⁄4-full with water. Submerge the ignition vessel
in the center of the ignition receptacle and visually inspect it for oxygen leaks. If the needle valve is not gas tight, tighten the
packing gland slightly. Do not fire the ignition vessel until all leaks are repaired. Allow cooling water to circulate around the
ignition vessel the entire time the it is in the receptacle. (Wa
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