ASTM D2572-97(2003)e1
(Test Method)Standard Test Method for Isocyanate Groups in Urethane Materials or Prepolymers
Standard Test Method for Isocyanate Groups in Urethane Materials or Prepolymers
SIGNIFICANCE AND USE
The percent NCO is used to establish unit ratios for stoichiometric reactions with co-reactants.
SCOPE
1.1 This test method covers the determination of the isocyanate group (NCO) content of a urethane intermediate or prepolymer.
1.2 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. For specific hazard statements, see Section 8.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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´1
Designation:D2572–97(Reapproved2003)
Standard Test Method for
Isocyanate Groups in Urethane Materials or Prepolymers
This standard is issued under the fixed designation D2572; 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.
This standard has been approved for use by agencies of the Department of Defense.
´ NOTE—Keywords were added editorially in July 2003.
1. Scope compounds is usually sufficiently low that their effect on the
determination is negligible.
1.1 This test method covers the determination of the isocy-
anate group (NCO) content of a urethane intermediate or
6. Apparatus
prepolymer.
6.1 Polyethylene Stoppers (or corks) covered with alumi-
1.2 This standard does not purport to address all of the
num foil to fit 250-mL Erlenmeyer flasks.
safety concerns, if any, associated with its use. It is the
6.2 Magnetic Stirrer with PTFE-fluorocarbon-covered stir-
responsibility of the user of this standard to establish appro-
ring bar.
priate safety and health practices and determine the applica-
6.3 Pipet, 25-mL.
bility of regulatory limitations prior to use. For specific hazard
6.4 Buret, 50- or 100-mL.
statements, see Section 8.
6.5 Analytical Balance.
2. Referenced Documents
7. Reagents
2.1 ASTM Standards:
7.1 Purity of Reagents—Reagent grade chemicals shall be
D841 Specification for Nitration Grade Toluene
used in all tests unless otherwise specified. Unless otherwise
3. Summary of Test Method indicated, it is intended that all reagents shall conform to the
specifications of the Committee on Analytical Reagents of the
3.1 The urethane prepolymer is allowed to react with an
American Chemical Society, where such specifications are
excess of di-n-butylamine in toluene (Note 1). After the
available. Other grades may be used, provided that it is first
reaction is complete, the excess of di-n-butylamine is deter-
ascertained that the reagent is of sufficiently high purity to
mined by back titration with standard hydrochloric acid.
permit its use without lessening the accuracy of the determi-
NOTE 1—Solvents other than toluene may be needed in some cases, for
nation.
example, anhydrous dimethylformamide (DMF), but the procedure has
7.2 Bromphenol Blue Indicator, Prepare 0.1 % solution by
not been evaluated using them.
mixing 0.10 g of acid, nonwater soluble bromphenol blue with
1.5 mLof 0.1 N sodium hydroxide solution and diluting to 100
4. Significance and Use
mL with distilled water.
4.1 The percent NCO is used to establish unit ratios for
7.3 Di-n-butylamine Solution, 0.1 N in dry toluene. Not
stoichiometric reactions with co-reactants.
standardized.
7.4 Hydrochloric Acid Solution, 0.1 N standardized using
5. Interferences
bromphenol blue indicator solution.
5.1 Phosgene, the carbamyl chloride of isocyanate, hydro-
7.5 Isopropyl Alcohol.
gen chloride, or any other acidic or basic impurities of
7.6 Toluene, anhydrous, conforming to Specification D841
sufficient strength will interfere. The concentration of these
or equivalent dried with molecular sieve pellets.
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.33 on Polymers and Resins. Burets and pipets shall conform to National Institute of Standards and
Current edition approved July 10, 2003. Published July 2003. Originally Technology tolerances.
approved in 1967. Last previous edition approved in 1997 as D2572 – 97. DOI: Reagent Chemicals, American Chemical Society Specifications, American
10.1520/D2572-97R03E01. Chemical Society, Washington, DC. For suggestions on the testing of reagents not
For referenced ASTM standards, visit the ASTM website, www.astm.org, or listed by the American Chemical Society, see Analar Standards for Laboratory
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Chemicals, BDH Ltd., Poole, Dorset, U.K., an
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