ASTM D3644-15(2022)

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

General Information

• Status: Published
• Publication Date: 30-Nov-2022
• ICS: 83.080.10 - Thermosetting materials
• Technical Committee: D21 - Polishes
• Drafting Committee: D21.02 - Raw Materials

Relations

• Refers: ASTM D329-07e1 - Standard Specification for Acetone <a href="#fn00002"></a>
• Effective Date: 01-Jun-2007
• Refers: ASTM D329-07 - Standard Specification for Acetone
• Effective Date: 01-Jun-2007
• Refers: ASTM D1193-06 - Standard Specification for Reagent Water
• Effective Date: 01-Mar-2006
• Refers: ASTM D329-02 - Standard Specification for Acetone
• Effective Date: 10-Dec-2002
• Refers: ASTM D329-99 - Standard Specification for Acetone
• Effective Date: 10-Dec-1999
• Refers: ASTM D1193-99e1 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999
• Refers: ASTM D1193-99 - Standard Specification for Reagent Water
• Effective Date: 10-Feb-1999

Overview

ASTM D3644-15(2022): Standard Test Method for Acid Number of Styrene-Maleic Anhydride Resins establishes a reliable procedure for determining the acid number in styrene-maleic anhydride (SMA) resins. The acid number reflects the amount of free acidity in a resin sample, which is a critical property for assessing resin functionality and quality control in manufacturing and end-use applications. This international standard supports consistent, accurate testing in accordance with globally recognized best practices for chemical and material analysis.

Key Topics

• Purpose and Significance

  • The test method measures the acid number, which indicates the functionality of SMA resins.
  • Acid functionality is essential for determining resin utility and is a significant metric in quality control for manufacturers and end users.
  • Because some anhydride groups hydrolyze during manufacturing, direct titration is inaccurate. This standard prescribes a method using excess alkali to hydrolyze anhydride groups, followed by a back-titration with standardized acid to determine total acid content by difference.

• Scope and Applicability

  • Covers measurement of free acidity in SMA resins only.
  • Values are stated exclusively in SI units.
  • Users are responsible for ensuring the method’s safe and appropriate use in their environment.

• Method Summary

  • Involves titrating the resin sample with sodium hydroxide, hydrolizing anhydride groups, then back-titrating with sulfuric acid.
  • Acid number is calculated as the amount (mg) of potassium hydroxide equivalent needed to neutralize acidic constituents in 1 g of resin under test conditions.

• Quality and Reproducibility

  • Precision allows duplicate results to differ by no more than a standard deviation of 0.8 acid number units.
  • Bias is defined such that results are valid only relative to this test method.

Applications

• Quality Control in Manufacturing

  • Routinely used to assess the consistency and quality of styrene-maleic anhydride resins during production and before product release.
  • Ensures SMA resins meet performance specifications for end-use.

• Material and Product Development

  • Assists R&D teams in evaluating new resin formulations or modifications by quantifying changes in acidic functionality.
  • Supports selection of appropriate resin types for specific applications in coatings, adhesives, and polishes.

• Regulatory and Compliance Testing

  • Provides a transparent, standardized method for demonstrating material conformity to international and customer requirements.
  • Useful reference in technical datasheets and regulatory submissions for resin-based products.

Related Standards

• ASTM D329 - Specification for Acetone: Defines purity requirements for acetone used in this test.
• ASTM D1193 - Specification for Reagent Water: Establishes water quality for reagent preparation.
• Other Relevant Methods
  • Additional ASTM methods for resin analysis and broader standards on titrimetric procedures may also be applicable in quality assurance laboratories.

Keywords: acid number, styrene-maleic anhydride resin, SMA resin, resin acidity, titration, quality control, ASTM D3644, chemical analysis, resin testing, international standard.

By implementing ASTM D3644-15(2022), organizations ensure reliable measurement of acid number in SMA resins, supporting product quality, regulatory compliance, and effective material selection.

Standards Content (Sample)

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.
Designation: D3644 − 15 (Reapproved 2022)
Standard Test Method for
Acid Number of Styrene-Maleic Anhydride Resins
This standard is issued under the fixed designation D3644; 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 4.2 Because some of the anhydride functionality has been
hydrolyzed in the manufacturing process, direct titration with
1.1 This test method covers the measurement of the free
base will produce erroneous data on the total acid content of
acidity present in styrene-maleic anhydride resins.
the fully hydrolyzed resin in use. This test method charges
1.2 The values stated in SI units are to be regarded as
excess alkali to hydrolize the anhydride functionality and
standard. No other units of measurement are included in this
neutralize the resulting acid. The remaining unreacted alkali is
standard.
thenbacktitratedwithastandardizedacidsolutionandtheacid
1.3 This standard does not purport to address all of the content is determined by difference.
safety concerns, if any, associated with its use. It is the
5. Reagents and Materials
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
5.1 Purity of Reagents—Reagent grade chemicals shall be
mine the applicability of regulatory limitations prior to use.
used in all tests. Unless otherwise indicated, it is intended that
1.4 This international standard was developed in accor-
all reagents shall conform to the specifications of the Commit-
dance with internationally recognized principles on standard-
tee onAnalytical Reagents of theAmerican Chemical Society,
ization established in the Decision on Principles for the
where such specifications are available. Other grades may be
Development of International Standards, Guides and Recom-
used, provided it is first ascertained that the reagent is of
mendations issued by the World Trade Organization Technical
sufficiently high purity to permit its use without lessening the
Barriers to Trade (TBT) Committee.
accuracy of the determination.
5.2 Purity of Water—Unless otherwise indicated, references
2. Referenced Documents
to water shall be understood to mean reagent water conforming
2.1 ASTM Standards:
to Specification D1193.
D329 Specification for Acetone
5.3 Acetone, conforming to the requirements described in
D1193 Specification for Reagent Water
Specification D329.
3. Terminology
5.4 Phenolphthalein Indicator Solution (20 g/L)—Dissolve
10 g of phenolphthalein in 100 mL of acetone.
3.1 Definitions:
3.1.1 acid number—the number of milligrams of potassium
5.5 Sodium Hydroxide, Standard Solution (0.1 N)—
hydroxide (KOH) required to neutralize the alkali-reactive
Dissolve7gof sodium hydroxide (NaOH) in 7 mL of water,
groups in1gof material under the conditions of test.
and filter the resulting solution through a glass mat in a Gooch
crucible with the aid of suction. Do not wash the residue.
4. Significance and Use
Dilute two thirds of the clear filtrate to 1 L with freshly boiled
4.1 This test method is used to determine the property of
water. Standardize against National Institute of Standards and
styrene-maleic anhydride resins functionality.Acid functional-
Technology standard sample of acid potassium phthalate No.
ity determines the utility of resin as well as being a significant
84, using phenolphthalein as the indicator. Do not adjust the
quality control test.
concentration of the solution, but calculate the normality.
5.6 Sulfuric Acid, Standard Solution (0.1 N)—Measure out
1 3mLofconcentratedsulfuricacid(H SO )(d = 1.84)andpour
ThistestmethodisunderthejurisdictionofASTMCommitteeD21onPolishes 2 4
and is the direct responsibility of Subcommittee D21.02 on Raw Materials.
Current edition approved Dec. 1, 2022. Published December 2022. Originally
approved in 1983. Last previous edition
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