ASTM D3644 - 15 (2022)

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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

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 appro-

priate safety, health, and environmental practices and deter-

mine the applicability of regulatory limitations prior to use.

1.4 This international standard was developed in accor-

dance with internationally recognized principles on standard-

ization established in the Decision on Principles for the

Development of International Standards, Guides and Recom-

mendations issued by the World Trade Organization Technical

Barriers to Trade (TBT) Committee.

2. Referenced Documents

2.1 ASTM Standards:

D329 Speciﬁcation for Acetone

D1193 Speciﬁcation for Reagent Water

3. Terminology

3.1 Deﬁnitions:

3.1.1 acid number—the number of milligrams of potassium

hydroxide (KOH) required to neutralize the alkali-reactive

groups in1gofmaterial under the conditions of test.

4. Signiﬁcance and Use

4.1 This test method is used to determine the property of

styrene-maleic anhydride resins functionality. Acid functional-

ity 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.

5. Reagents and Materials

5.1 Purity of Reagents—Reagent grade chemicals shall be

used in all tests. Unless otherwise indicated, it is intended that

all reagents shall conform to the speciﬁcations of the Commit-

tee on Analytical Reagents of the American Chemical Society,

where such speciﬁcations are available.

Other grades may be

used, provided it is ﬁrst ascertained that the reagent is of

sufficiently high purity to permit its use without lessening the

accuracy of the determination.

5.2 Purity of Water—Unless otherwise indicated, references

to water shall be understood to mean reagent water conforming

to Speciﬁcation D1193.

5.3 Acetone, conforming to the requirements described in

Speciﬁcation D329.

5.4 Phenolphthalein Indicator Solution (20 g/L)—Dissolve

10 g of phenolphthalein in 100 mL of acetone.

5.5 Sodium Hydroxide, Standard Solution (0.1 N)—

Dissolve7gofsodium hydroxide (NaOH) in 7 mL of water,

and ﬁlter the resulting solution through a glass mat in a Gooch

crucible with the aid of suction. Do not wash the residue.

Dilute two thirds of the clear ﬁltrate to 1 L with freshly boiled

water. Standardize against National Institute of Standards and

Technology standard sample of acid potassium phthalate No.

84, using phenolphthalein as the indicator. Do not adjust the

concentration of the solution, but calculate the normality.

5.6 Sulfuric Acid, Standard Solution (0.1 N)—Measure out

3 mL of concentrated sulfuric acid (H

)(d= 1.84) and pour

This test method is under the jurisdiction of ASTM Committee D21 on Polishes

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 approved in 2015 as D3644 – 15. DOI:

10.1520/D3644-15R22.

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.

Reagent Chemicals, American Chemical Society Speciﬁcations, American

Chemical Society, Washington, DC. For suggestions on the testing of reagents not

listed by the American Chemical Society, see Analar Standards for Laboratory

Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia

and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,

MD.

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.

it slowly, and with constant stirring, into about 100 mL of

water. Cool to room temperature, mix thoroughly, and dilute to

1 L. Standardize against 0.1 NNaOH solution, as prepared in

4.5, using phenolphthalein as the indicator. Do not adjust the

concentration of the solution, but calculate the normality.

6. Procedure

6.1 Weigh 0.1 g of the sample to the nearest 0.0001 g into

a 250 mL Erlenmeyer ﬂask.

6.2 Add 150 mL 62 mL of acetone to the ﬂask, stopper it,

and swirl it until the sample is dissolved. All 0.2 mL of

phenolphthalein indicator solution and titrate with NaOH

solution to the end point, a faint pink color which persists for

30 s. Then add 2.0 mL of additional NaOH solution, stopper

the ﬂask, and allow it to stand for exactly 10 min.

NOTE 1—If a precipitate forms during the titration, discard the sample

and repeat the test using a smaller sample or a greater volume of acetone,

or both. A slight haze can be tolerated and does not interfere with the test.

6.3 Back titrate with 0.1 NH

to the end point, at which

the sample turns colorless and remains so for 30 s.

6.4 Using the same procedure, titrate a blank composed of

150 mL of acetone and 5 mL of water.

7. Calculation

7.1 Calculate the acid number as follows:

Blank 5

Acid number 5

1blank

356.1

= millilitres of H

= normality of H

= millilitres of NaOH solution,

= normality of NaOH solution, and

C= weight of sample.

8. Report

8.1 Report the acid number of the resin tested, to the nearest

whole number.

9. Precision and Bias

9.1 Precision—Duplicate results by the same operator shall

not be considered suspect unless they differ by more than a

standard deviation of 0.8.

9.2 Bias—This test has no bias because the values produced

are deﬁned only in terms of this test method.

10. Keywords

10.1 acid number; free acid; polish; resins; SMA resins;

styrene-maletic anhydrid resin; titration

ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned

in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk

of infringement of such rights, are entirely their own responsibility.

This standard is subject to revision at any time by the responsible technical committee and must be reviewed every ﬁve years and

if not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standards

and should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the

responsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you should

make your views known to the ASTM Committee on Standards, at the address shown below.

This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,

United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the above

address or at 610-832-9585 (phone), 610-832-9555 (fax), or service@astm.org (e-mail); or through the ASTM website

(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222

Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http://www.copyright.com/

D3644 − 15 (2022)

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摘要：

ASTM D3644 - 15 (2022) 是一份由美国材料与试验协会（ASTM）发布的最新版本标准规范，主要针对特定橡胶材料或产品的性能测试方法进行规定。该标准于2015年首次发布，并于2022年重新批准确认，确保其技术内容仍符合当前工业应用需求。文档详细描述了样品的制备、测试条件、仪器要求以及数据评估流程，旨在帮助制造商、质检机构和研究人员在统一标准下评估橡胶的物理、机械或化学特性。通过遵循ASTM D3644，用户可以有效提升产品的一致性与可靠性，降低生产与使用中的风险。本规范适用于橡胶

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