ASTM D7253-06(2011)e1

Standard Test Method for Polyurethane Raw Materials: Determination of Acidity as Acid Number for Polyether Polyols

SIGNIFICANCE AND USE
This test method is suitable for quality control, as a specification test, and for research. Acid numbers indicate the extent of any neutralization reaction of the polyol with acids. The results of this method measure batch-to-batch uniformity and are used as correction factors in calculating true hydroxyl numbers.
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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.
Note 1—There is no known ISO equivalent to this standard.

General Information

• Status: Historical
• Publication Date: 31-Aug-2011
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

Relations

• Replaces: ASTM D7253-06 - Standard Test Method for Polyurethane Raw Materials: Determination of Acidity as Acid Number for Polyether Polyols
• Effective Date: 01-Sep-2011

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
´1
Designation: D7253 − 06(Reapproved 2011)
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.
´ NOTE—Reapproved with editorial changes in September 2011.
1. Scope 4. Summary of Test Method
1.1 This test method measures the acidic constituents in
4.1 The sample is dissolved in 2-propanol. The resulting
polyether polyols and reports the results as acid number. The
single-phase solution is titrated at room temperature with 0.02
typical acid number range is 0-0.1 mg KOH/g sample. (See
N methanolic potassium hydroxide solution to an end point
Note 1.)
indicated by the color change (pink endpoint) of the added
phenolphthalein.
1.2 The values stated in SI units are to be regarded as
NOTE 2—Phenolphthalein is the indicator of choice based on published
standard. No other units of measurement are included in this
hydroxyl number methods that include an acid number correction. Other
standard.
indicators can be chosen if specific acids are of interest. Bromothymol
1.3 This standard does not purport to address all of the
blue (green endpoint) can be used for stronger acids (pKa’s < ~4) and
thymolphthalein (blue endpoint) can be used for weak acids (pKa’s > ~7).
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Significance and Use
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
5.1 This test method is suitable for quality control, as a
specification test, and for research. Acid numbers indicate the
NOTE 1—There is no known ISO equivalent to this standard.
extent of any neutralization reaction of the polyol with acids.
The results of this method measure batch-to-batch uniformity
2. Referenced Documents
and are used as correction factors in calculating true hydroxyl
2.1 ASTM Standards:
numbers.
D883 Terminology Relating to Plastics
E691 Practice for Conducting an Interlaboratory Study to
6. Interferences
Determine the Precision of a Test Method
6.1 Samples or constituents that are highly-colored will
3. Terminology
interfere with or prevent the use of this test method.
3.1 Definitions: For definitions of terms used in this test
7. Apparatus
method see Terminology D883.
7.1 Buret, 10 mL, can be manual or automatic.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 acid number—the quantity of base, expressed in mil-
7.2 Graduated cylinder, 10 mL, maximum.
ligramsofpotassiumhydroxide,thatisrequiredtotitrateacidic
7.3 Balance, analytical with sensitivity of at least 60.0001
constituents in1gof sample.
g.
7.4 Erlenmeyer flask, at least 250 mL.
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
7.5 Stirring bars or stirring rods.
and is the direct responsibility of Subcommittee D20.22 on Cellular Materials -
Plastics and Elastomers.
Current edition approved Sept. 1, 2011. Published October 2011. Originally
8. Reagents and Materials
approved in 2006. Last previous edition approved in 2006 as D7253 - 06.
DOI:10.1520/D7253-06R11E01.
8.1 Purity of Reagents—Use reagent-grade chemicals in all
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
tests.Unlessotherwiseindicated,itisintendedthatallreagents
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
conform to the specifications of the Committee on Analytical
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Reagents of the American Chemical Society where such
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´1
D7253 − 06 (2011)
TABLE 1 Round Robin Data for Acid Number (mg KOH/g) in
specifications are available. Other grades can be used pro-
Accordance with Practice E691
vided it is first ascertained that the reagent is of sufficiently
A B C D E
Material Average S S r R n
high purity to permit its use without lessening the accuracy of r R
1 0.026 0.001 0.005 0.003 0.013 7
the determination.
2 0.015 0.001 0.005 0.004 0.014 7
3 0.016 0.002 0.005 0.005 0.013 7
8.2 Phenolphthalein, Indicator Grade.
4 0.105 0.001 0.008 0.004 0.022 6
8.3 Phenolphthalein Indicator Solution—Dissolve1gof
A
S = within-laboratory standard deviation of the replicates.
r
B
phenolphthalein in 100 mL of methanol.
S = between-laboratory standard deviation of the averages.
R
C
r = within-laboratory repeatability limit = 2.8*S .
r
8.4 Potassium Hydroxide Standard Solution (0.02 N)—
D
R = between-laboratory reproducibility limit = 2.8*S .
R
E
Prepare and standardize a 0.02 N methanolic pot
...