Standard Active Last Updated: Jul 19, 2021
ASTM D4274-21

Standard Test Methods for Testing Polyurethane Raw Materials: Determination of Hydroxyl Numbers of Polyols

Significance and Use

5.1 These test methods are suitable for research and as quality control and specification tests. It is necessary to know the hydroxyl contents of polyols in order to formulate polyurethane systems.


1.1 These test methods measure the hydroxyl groups in polyester and polyether polyols containing primary and secondary hydroxyl groups. They also apply to many other hydroxyl-containing substances.

1.1.1 Test Method A—Acetic Anhydride Pressure Bottle, recommended for polyesters.

1.1.2 Test Method B—Phthalic Anhydride Pressure Bottle, recommended for polyethers and polyesters.

1.1.3 Test Method C—Phthalic Anhydride Reflux, recommended for polyethers and polyesters.

1.1.4 Test Method D—Imidazole–Catalyzed Phthalic Anhydride Pressure Bottle, recommended for polyethers, polyesters, polymer polyols, and amine-initiated polyols.

1.1.5 Test Method E—Imidazole-Catalyzed Pyromellitic Dianhydride Esterification, recommended for polyols used for flexible and rigid polyurethane foams and urethane elastomers. It is recommended for polyester polyols, polyether polyols, amine-started polyols, and polymer polyols (polyacrylonitrile/copolystyrene-based).

1.2 Another ASTM test method for measuring hydroxyl groups is Test Method E222.

1.3 The values stated in SI units are to be regarded as the standard.

1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

Note 1: This standard, ISO 14900 and ISO 6796 address the same subject matter, but differ in technical content.

1.5 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.

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Book of Standards Volume: 08.02
Developed by Subcommittee: D20.22
Pages: 10
DOI: 10.1520/D4274-21
ICS Code: 83.080.20