ASTM D7253-06
(Test Method)Standard Test Method for Polyurethane Raw Materials: Determination of Acidity as Acid Number for Polyether Polyols
Standard Test Method for Polyurethane Raw Materials: Determination of Acidity as Acid Number for Polyether Polyols
SCOPE
1.1 This test method measures the acidic constituents in polyether polyols and reports the results as acid number. The typical acid number range is 0-0.1 mg KOH/g sample. (See Note 1.)
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.Note 1
There is no known ISO equivalent to this standard.
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:D7253–06
Standard Test Method for
Polyurethane Raw Materials: Determination of Acidity as
Acid Number for Polyether Polyols
This standard is issued under the fixed designation D7253; 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.
hydroxyl number methods that include an acid number correction. Other
1. Scope
indicators can be chosen if specific acids are of interest. Bromothymol
1.1 This test method measures the acidic constituents in
blue (green endpoint) can be used for stronger acids (pKa’s < ~4) and
polyether polyols and reports the results as acid number. The
thymolphthalein (blue endpoint) can be used for weak acids (pKa’s > ~7).
typical acid number range is 0-0.1 mg KOH/g sample. (See
5. Significance and Use
Note 1.)
1.2 This standard does not purport to address all of the
5.1 This test method is suitable for quality control, as a
safety concerns, if any, associated with its use. It is the
specification test, and for research. Acid numbers indicate the
responsibility of the user of this standard to establish appro-
extent of any neutralization reaction of the polyol with acids.
priate safety and health practices and determine the applica-
The results of this method measure batch-to-batch uniformity
bility of regulatory limitations prior to use.
and are used as correction factors in calculating true hydroxyl
numbers.
NOTE 1—There is no known ISO equivalent to this standard.
6. Interferences
2. Referenced Documents
6.1 Samples or constituents that are highly-colored will
2.1 ASTM Standards:
interfere with or prevent the use of this test method.
D883 Terminology Relating to Plastics
E691 Practice for Conducting an Interlaboratory Study to
7. Apparatus
Determine the Precision of a Test Method
7.1 Buret, 10 mL, can be manual or automatic.
3. Terminology
7.2 Graduated cylinder, 10 mL, maximum.
7.3 Balance, analytical with sensitivity of at least
3.1 Definitions: For definitions of terms used in this test
60.0001 g.
method see Terminology D883.
7.4 Erlenmeyer flask, at least 250 mL.
3.2 Definitions of Terms Specific to This Standard:
7.5 Stirring bars or stirring rods.
3.2.1 acid number—the quantity of base, expressed in
milligrams of potassium hydroxide, that is required to titrate
8. Reagents and Materials
acidic constituents in1gof sample.
8.1 Purity of Reagents—Use reagent-grade chemicals in all
4. Summary of Test Method
tests. Unless otherwise indicated, it is intended that all reagents
conform to the specifications of the Committee on Analytical
4.1 The sample is dissolved in 2-propanol. The resulting
Reagents of the American Chemical Society where such
single-phase solution is titrated at room temperature with 0.02
specifications are available. Other grades can be used pro-
N methanolic potassium hydroxide solution to an end point
vided it is first ascertained that the reagent is of sufficiently
indicated by the color change (pink endpoint) of the added
high purity to permit its use without lessening the accuracy of
phenolphthalein.
the determination.
NOTE 2—Phenolphthalein is the indicator of choice based on published
8.2 Phenolphthalein, Indicator Grade.
8.3 Phenolphthalein Indicator Solution—Dissolve1gof
phenolphthalein in 100 mL of methanol.
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
and is the direct responsibility of Subcommittee D20.22 on Cellular Materials—
Plastics and Elastomers.
Current edition approved April 1, 2006. Published April 2006. DOI: 10.1520/ Reagent Chemicals, American Chemical Society Specifications, American
D7253-06. 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. and the United States Phamacopeia and
Standards volume information, refer to the standard’s Document Summary page on National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
the ASTM website. MD.
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D7253–06
TABLE 1 Round Robin Data for Acid Number (mg KOH/g) in
8.4 Potassium Hydroxide Standard Solution (0.02 N)—
Accordance with Practice E691
Prepare and standardize a 0.02 N methanolic potassium hy-
A B C D E
Material Average S S r R n
droxide solution. (1.32 g KOH p
...
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