ASTM D7253-16

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

SIGNIFICANCE AND USE
5.1 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.  
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-2016
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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
Designation: D7253 − 16
Standard Test Method for
Polyurethane Raw Materials: Determination of Acidity as
1
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.
1. Scope* N methanolic potassium hydroxide solution to an end point
indicated by the color change (pink endpoint) of the added
1.1 This test method measures the acidic constituents in
phenolphthalein.
polyether polyols and reports the results as acid number. The
NOTE 2—It is permissible to use automatic titrators using a potentio-
typical acid number range is 0-0.1 mg KOH/g sample. (See
metric endpoint for the titration portion of this test provided the automatic
Note 1.)
titration method is tested to obtain at least equivalent results to the manual
titration.
1.2 The values stated in SI units are to be regarded as
NOTE 3—Phenolphthalein is the indicator of choice based on published
standard.
hydroxyl number methods that include an acid number correction. Other
1.3 This standard does not purport to address all of the
indicators can be chosen if specific acids are of interest. Bromothymol
safety concerns, if any, associated with its use. It is 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).
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5. Significance and Use
bility of regulatory limitations prior to use.
5.1 This test method is suitable for quality control, as a
NOTE 1—There is no known ISO equivalent to this standard.
specification test, and for research. Acid numbers indicate the
2. Referenced Documents
extent of any neutralization reaction of the polyol with acids.
2
The results of this method measure batch-to-batch uniformity
2.1 ASTM Standards:
and are used as correction factors in calculating true hydroxyl
D883 Terminology Relating to Plastics
numbers.
E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
6. Interferences
3. Terminology
6.1 Samples or constituents that are highly-colored will
3.1 Definitions—For definitions of terms used in this test
interfere with or prevent the use of this test method. In this
method see Terminology D883.
case, a potentiometric titration using an autotitrator is
recommended, see Note 2.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 acid number—the quantity of base, expressed in mil-
7. Apparatus
ligramsofpotassiumhydroxide,thatisrequiredtotitrateacidic
constituents in1gof sample.
7.1 Buret, 10 mL, can be manual or automatic.
4. Summary of Test Method
7.2 Graduated cylinder, 10 mL, maximum.
4.1 The sample is dissolved in 2-propanol. The resulting
7.3 Balance, analytical with sensitivity of at least 60.0001
single-phase solution is titrated at room temperature with 0.02
g.
7.4 Erlenmeyer flask, at least 250 mL capacity.
1
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, 2016. Published September 2016. Originally
8. Reagents and Materials
ɛ1
approved in 2006. Last previous edition approved in 2011 as D7253 - 11(2011) .
DOI:10.1520/D7253-16.
8.1 Purity of Reagents—Use reagent-grade chemicals in all
2
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
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7253 − 16
3
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 Phenolph
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
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.
´1
Designation: D7253 − 06 (Reapproved 2011) D7253 − 16
Standard Test Method for
Polyurethane Raw Materials: Determination of Acidity as
1
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.
1
ε NOTE—Reapproved with editorial changes in September 2011.
1. Scope 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions—Definitions:For definitions of terms used in this test method see Terminology D883.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 acid number—the quantity of base, expressed in milligrams of potassium hydroxide, that is required to titrate acidic
constituents in 1 g of sample.
4. Summary of Test Method
4.1 The sample is dissolved in 2-propanol. The resulting single-phase solution is titrated at room temperature with 0.02 N
methanolic potassium hydroxide solution to an end point indicated by the color change (pink endpoint) of the added
phenolphthalein.
NOTE 2—It is permissible to use automatic titrators using a potentiometric endpoint for the titration portion of this test provided the automatic titration
method is tested to obtain at least equivalent results to the manual titration.
NOTE 3—Phenolphthalein is the indicator of choice based on published hydroxyl number methods that include an acid number correction. Other
indicators can be chosen if specific acids are of interest. Bromothymol 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).
5. Significance and Use
5.1 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.
1
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plastics
and Elastomers.
Current edition approved Sept. 1, 2011Sept. 1, 2016. Published October 2011September 2016. Originally approved in 2006. Last previous edition approved in 20062011
ɛ1
as D7253 - 06.D7253 - 11(2011) DOI:10.1520/D7253-06R11E01. DOI:10.1520/D7253-16.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7253 − 16
6. Interferences
6.1 Samples or constituents that are highly-colored will interfere with or prevent the use of this test method. In this case, a
potentiometric titration using an autotitrator is recommended, see Note 2.
7. Apparatus
7.1 Buret, 10 mL, can be manual or automatic.
7.2 Graduated cylinder, 10 mL, maximum.
7.3 Balance, analytical with sensitivity of at least 60.0001 g.
7.4 Erlenmeyer flask, at least 250 mL. mL capacity.
7.5 Stirring bars or stirring rods.
8. Reagents and Materials
8.1 Purity of Reagents—Use reagent-grade chemicals in all tests. Unless otherwise indicated, it is intended that all reagents
conform to the specificatio
...