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 Bottlerecommended for polyesters.

1.1.2 Test Method B-Phthalic Anhydride Pressure Bottlerecommended for polyethers and polyesters.

1.1.3 Test Method C-Phthalic Anhydride Refluxrecommended for polyethers and polyesters.

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

1.1.5 Test Method EImidazole-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 Other ASTM test methods for measuring hydroxyl groups are Test Methods D 1957 and E 222 (see Note 0).

Note 1 - Test Method C is essentially similar to ISO 6796-1981, but there are some differences in the concentrations used and some procedural details. There are currently no data available for comparing the results of Test Method C to those of ISO 6796-1981.

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