Standard Historical Last Updated: Dec 28, 2022
ASTM D3644-15

Standard Test Method for Acid Number of Styrene-Maleic Anhydride Resins

Significance and Use

4.1 This test method is used to determine the property of styrene-maleic anhydride resins functionality. Acid functionality determines the utility of resin as well as being a significant quality control test.

4.2 Because some of the anhydride functionality has been hydrolyzed in the manufacturing process, direct titration with base will produce erroneous data on the total acid content of the fully hydrolyzed resin in use. This test method charges excess alkali to hydrolize the anhydride functionality and neutralize the resulting acid. The remaining unreacted alkali is then back titrated with a standardized acid solution and the acid content is determined by difference.


1.1 This test method covers the measurement of the free acidity present in styrene-maleic anhydride resins.

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.

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Book of Standards Volume: 15.04
Developed by Subcommittee: D21.02
Pages: 2
DOI: 10.1520/D3644-15
ICS Code: 83.080.10