ASTM D4662-20

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Designation: D4662 − 15 D4662 − 20
Standard Test Methods for
Polyurethane Raw Materials: Determination of Acid and
Alkalinity Numbers of Polyols
This standard is issued under the fixed designation D4662; 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 measure the acidic and basic constituents in polyols and other materials of high acidity or alkalinity that
are soluble in mixtures of toluene and ethyl alcohol. These test methods do not apply to polyethers. (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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
NOTE 1—There is no known ISO equivalent to this standard.
NOTE 1—There is no known ISO equivalent to this standard.
1.3 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
E456 Terminology Relating to Quality and Statistics
E2935 Practice for Conducting Equivalence Testing in Laboratory Applications
3. Terminology
3.1 Definitions—For definitions of terms used in these test methods see Terms used in this standard are defined in accordance
with Terminology D883. , unless otherwise specified. For terms relating to precision and bias and associated issues, the terms used
in this standard are defined in accordance with Terminology E456.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 acid number—number, n—the quantity of base, expressed in milligrams of potassium hydroxide, that is required to titrate
acidic constituents present in 1 g of sample.
3.2.2 alkalinity number—number, n—the quantity of base, expressed as milligrams of potassium hydroxide, present in 1 g of
sample.
4. Summary of Test Method
4.1 The sample is dissolved in a mixture of toluene and ethyl alcohol. The resulting single-phase solution is titrated at room
temperature with alcoholic potassium hydroxide solution, to the end point indicated by the color change of added phenolphthalein.
Alkalinity numbers are determined by back-titration after adding excess hydrochloric acid. The endpoint of these titrations also
can be determined potentiometrically.
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 Sept. 1, 2015July 1, 2020. Published September 2015July 2020. Originally approved in 1987. Last previous edition approved in 20112015 as
ε1
D4662 - 08D4662 - 15.(2011) . DOI: 10.1520/D4662-15.10.1520/D4662-20.
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.
*A Summary of Changes section appears at the end of this standard
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D4662 − 20
5. Significance and Use
5.1 These test methods are suitable for quality control, as specification tests, and for research. The acid and alkalinity numbers
indicate the extent of a reaction with acids. The results are measures of batch-to-batch uniformity and are typically used as
correction factors in calculating hydroxyl number.
6. Reagents and Materials
6.1 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 allowed, provided it is first ascertained that the reagent is of sufficiently high purity
to permit its use without lessening the accuracy of the determination.
6.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by
Type I of Specification D1193.
6.3 Ethyl Alcohol, 95 %.95 % (minimum purity).
6.4 Hydrochloric Acid (0.1 N)—Prepare a 0.1 N solution of hydrochloric acid (HCl). Standardization is unnecessary.
6.5 Phenolphthalein Indicator Solution—Dissolve 0.5 g of phenolphthalein in 100 mL of a mixture of equal volumes of water
and ethyl alcohol. Add a slight excess of 0.1 N NaOH solution (pink color) and then just neutralize (colorless) with 0.1 N HCl.
6.6 Potassium Hydroxide, Standard Alcoholic Solution (0.1 N)—Dissolve 5.61 g of potassium hydroxide (KOH) in 10 mL of
carbon dioxide-free water and dilute to 1 L with ethyl alcohol. Store the solution in a chemical-resistant dispensing bottle protected
by a guard tube containing soda-lime or ascarite. Standardize frequently enough to detect changes of 0.0005 N, preferably against
pure potassium acid phthalate (KHC H O , 0.8 to 0.9 g) in about 100 mL of carbon dioxide-free water, using phenolphthalein to
8 4 4
detect the end point.
6.7 Sodium Hydroxide, Standard Solution (0.1 N)—Prepare and standardize a 0.1 N solution of sodium hydroxide (NaOH).
Follow 6.6 for instructions on preparing and standardizing solution.
6.8 Titration Solvent—Mix equal volumes of toluene and ethyl alcohol.
7. Sampling
7.1 Polyesters usually contain molecules covering an appreciable range of molecular weights. These have a tendency to
fractionate during solidification. Unless the material is a finely ground solid, it is necessary to melt (using as low a temperature
as necessary) and mix the resin well before removing a sample for analysis. Because many polyols are hygroscopic, one must take
care to provide minimum exposure to atmospheric moisture during the sampling.
TEST METHOD A—ACID NUMBER
8. Procedure
8.1 Into a 250-mL Erlenmeyer flask
...