ASTM D2121-23

Standard Test Methods for Polymer Content of Styrene Monomer

SIGNIFICANCE AND USE
5.1 This test method can be used for determining polymer concentrations in styrene monomer.  
5.2 This test method will not detect dimers and trimers.  
5.3 This test method can be used for plant control and for specification analysis.
SCOPE
1.1 These test methods cover the determination of the polymer content of styrene monomer. It should be noted, however, that dimers and trimers are not measured by these test methods.  
1.2 Test Method A, which is based on the use of a spectrophotometer or photometer, is intended for the quantitative determination of the polymer content of styrene monomer in concentrations up to 15 mg/kg. Samples containing more than 15 mg/kg of polymer must be suitably diluted before measurement. The limit of detection (LOD) is 1.2 mg/kg and the limit of quantitation (LOQ) is 4.0 mg/kg. LOD and LOQ were calculated using the last sample in Table 1.  
1.3 Test Method B is a rapid visual procedure that is intended for the approximate evaluation of polymer to a maximum concentration of 1.0 mass %. Samples having a polymer content of 1.0 mass % or greater should be suitably diluted prior to measurement.  
1.4 In determining the conformance of the test results using this method to applicable specifications, results shall be rounded off in accordance with the rounding-off method of Practice E29.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 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. For specific hazard statements, see Section 9.  
1.7 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: 31-Oct-2023
• ICS: 71.080.15 - Aromatic hydrocarbons
• Technical Committee: D16 - Aromatic, Industrial, Specialty and Related Chemicals
• Drafting Committee: D16.07 - Styrene, Ethylbenzene and C9 and C10 Aromatic Hydrocarbons

Relations

• Replaces: ASTM D2121-16 - Standard Test Methods for Polymer Content of Styrene Monomer
• Effective Date: 01-Nov-2023
• Referred By: ASTM D2827-19 - Standard Specification for Styrene Monomer
• Effective Date: 01-Nov-2023
• Referred By: ASTM D4790-23 - Standard Terminology of Aromatic Hydrocarbons and Related Chemicals
• Effective Date: 01-Nov-2023

Overview

ASTM D2121-23: Standard Test Methods for Polymer Content of Styrene Monomer establishes procedures for determining the amount of polymer present in styrene monomer. As styrene monomer is widely used in the production of polystyrene plastics, controlling its purity is essential for process efficiency and final product quality. This standard outlines two primary test methods suitable for plant control and specification analysis:

• Test Method A: A quantitative approach using spectrophotometric or photometric analysis.
• Test Method B: A rapid, qualitative visual assessment.

These methods help ensure reliable measurement of polymer content in styrene monomer, supporting compliance with quality requirements in the chemical and plastics industries.

Key Topics

1. Purpose and Applicability

• Measures polymer content in styrene monomer for concentrations up to 15 mg/kg (Test Method A) and up to 1.0% by mass (Test Method B).
• Excludes the detection of dimers and trimers.
• Results are intended for use in plant operations and product specification checks.

2. Test Methods

• Test Method A: Spectrophotometric/Photometric Analysis
  • Quantitatively determines polymer concentrations up to 15 mg/kg.
  • Uses the difference in turbidity when methanol is added to the sample.
  • Requires dilution if polymer content exceeds 15 mg/kg.
  • Limit of detection (LOD): 1.2 mg/kg; limit of quantitation (LOQ): 4.0 mg/kg.
• Test Method B: Visual Evaluation
  • Quickly estimates polymer levels up to 1.0% by weight.
  • Based on visual comparison of turbidity after methanol addition.
  • Suitable for rapid screening and routine plant checks.

3. Reporting and Precision

• Results are reported in accordance with ASTM E29 for significant digits.
• Precision and reproducibility data are provided to support result reliability.
• Laboratories are encouraged to maintain robust QA/QC systems and participate in interlaboratory testing for consistent results.

4. Safety and Compliance

• Users must follow appropriate safety, environmental, and regulatory practices.
• The standard references current OSHA regulations for handling styrene monomer.

Applications

ASTM D2121-23 is vital for:

• Chemical Manufacturing: Ensuring the purity of styrene monomer feeds in polystyrene production to prevent process disturbances and ensure product quality.
• Quality Control: Providing reliable measurement techniques for in-process and final product evaluation.
• Specification Testing: Supporting both supplier and customer requirements for styrene monomer purity in contracts and transactions.
• Regulatory Compliance: Helping organizations comply with industry and safety regulations pertaining to hazardous chemicals.

These test methods are practical tools for routine plant control, research, and quality auditing in any facility handling or producing styrene monomer.

Related Standards

• ASTM D2827: Specification for Styrene Monomer - covers the general requirements for styrene.
• ASTM D3437: Practice for Sampling and Handling Liquid Cyclic Products - details proper sampling techniques.
• ASTM D4790: Terminology of Aromatic Hydrocarbons and Related Chemicals - provides definitions relevant to aromatic hydrocarbons.
• ASTM D6809: Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons - outlines QA/QC best practices.
• ASTM E29: Practice for Using Significant Digits in Test Data - guides reporting of test results.
• ASTM E691: Practice for Conducting an Interlaboratory Study - methodology for multi-laboratory testing.

These related ASTM standards support robust methods for sampling, handling, analysis, and quality assurance of styrene monomer and associated products.

Keywords: ASTM D2121-23, polymer content, styrene monomer, test methods, spectrophotometric analysis, visual evaluation, quality control, chemical manufacturing, polymer purity standards.

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: D2121 − 23
Standard Test Methods for
Polymer Content of Styrene Monomer
This standard is issued under the fixed designation D2121; 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* mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.1 These test methods cover the determination of the
polymer content of styrene monomer. It should be noted,
2. Referenced Documents
however, that dimers and trimers are not measured by these test
methods.
2.1 ASTM Standards:
D2827 Specification for Styrene Monomer
1.2 Test Method A, which is based on the use of a spectro-
D3437 Practice for Sampling and Handling Liquid Cyclic
photometer or photometer, is intended for the quantitative
Products
determination of the polymer content of styrene monomer in
D4790 Terminology of Aromatic Hydrocarbons and Related
concentrations up to 15 mg/kg. Samples containing more than
Chemicals
15 mg/kg of polymer must be suitably diluted before measure-
D6809 Guide for Quality Control and Quality Assurance
ment. The limit of detection (LOD) is 1.2 mg/kg and the limit
Procedures for Aromatic Hydrocarbons and Related Ma-
of quantitation (LOQ) is 4.0 mg/kg. LOD and LOQ were
terials
calculated using the last sample in Table 1.
E29 Practice for Using Significant Digits in Test Data to
1.3 Test Method B is a rapid visual procedure that is
Determine Conformance with Specifications
intended for the approximate evaluation of polymer to a
E691 Practice for Conducting an Interlaboratory Study to
maximum concentration of 1.0 mass %. Samples having a
Determine the Precision of a Test Method
polymer content of 1.0 mass % or greater should be suitably
2.2 Other Document:
diluted prior to measurement.
OSHA Regulations, 29CFR paragraphs 1910.1000 and
1.4 In determining the conformance of the test results using
1910.1200
this method to applicable specifications, results shall be
rounded off in accordance with the rounding-off method of
3. Terminology
Practice E29.
3.1 See Terminology D4790 for definition of terms used in
1.5 The values stated in SI units are to be regarded as
this test method.
standard. No other units of measurement are included in this
standard.
TEST METHOD A—DETERMINATION OF POLYMER
IN STYRENE MONOMER SPECTROSCOPIC
1.6 This standard does not purport to address all of the
METHOD
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4. Summary of Test Method
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to
4.1 This test method utilizes the fact that polymers present
use. For specific hazard statements, see Section 9.
in the monomers are insoluble in methanol. The polymer
1.7 This international standard was developed in accor-
content of styrene monomer is determined by measurement of
dance with internationally recognized principles on standard-
the degree of turbidity produced by the addition of dry
ization established in the Decision on Principles for the
methanol to the styrene sample.
Development of International Standards, Guides and Recom-
1 2
These test methods are under the jurisdiction of ASTM Committee D16 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Aromatic, Industrial, Specialty and Related Chemicals and are the direct responsi- contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
bility of Subcommittee D16.07 on Styrene, Ethylbenzene and C9 and C10 Aromatic Standards volume information, refer to the standard’s Document Summary page on
Hydrocarbons. the ASTM website.
Current edition approved Nov. 1, 2023. Published November 2023. Originally Available from U.S. Government Printing Office Superintendent of Documents,
approved in 1962. Last previous edition approved in 2016 as D2121 – 16. DOI: 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
10.1520/D2121-23. www.access.gpo.gov.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2121 − 23
TABLE 1 Styrene (mg/kg)
8.4.1 Prepare polystyrene as follows: wash 50 mL of styrene
Repeatability Reproducibility monomer twice with equal volumes of 1 N NaOH solution and
A
Average
Material Limit Limit
¯
twice with equal volumes of water. After the second water
X
r R
wash, filter the styrene through two layers of rapid filtering
Sample 1 — 2 mg/kg 2.6 0.3 0.7
ready folded filter paper. Pour about 20 mL of this styrene
Sample 2 — 5 mg/kg 4.1 0.7 1.3
Sample 3 — 6 mg/kg 7.7 1.1 3.4
monomer into a test tube and heat in an oven at 100 °C for 24 h
A
to promote polymerization. At the end of this time, remove the
The average of the laboratories’ calculated averages.
polystyrene from the test tube by breaking the tube and
discarding all glass. Grind the polymer plug to a fine powder in
an agate mortar.
5. Significance and Use 8.4.2 Commercially available high-purity polystyrene pel-
lets can be used; however, high-molecular weight polystyrene
5.1 This test method can be used for determining polymer
(>150 000 molecular weight) should be specified.
concentrations in styrene monomer.
8.5 Styrene Monomer, conforming to Specification D2827
5.2 This test method will not detect dimers and trimers.
(CAS 100-42-5).
5.3 This test method can be used for plant control and for
8.6 Toluene, dry (CAS 108-88-3).
specification analysis.
9. Hazards
6. Interferences
9.1 Styrene monomer is flammable and polymerizes exo-
6.1 Small changes in turbidity may occur with time. It is,
thermically on contact with peroxides, mineral acids and
therefore, important that the absorbance of calibration mixtures
aluminum chloride.
and samples be determined after standing the same length of
time.
9.2 Styrene monomer both in liquid and vapor state, when in
sufficient concentrations, acts as an irritant to the eyes and
6.2 Hexane is used for two reasons:
respiratory tract.
6.2.1 To block out any color in the styrene, and
6.2.2 To indicate dissolved water in the styrene.
9.3 Consult current OSHA regulations, local regulations,
and suppliers’ Safety Data Sheets for all materials used in these
7. Apparatus
test methods.
7.1 Pipets, 10 mL and 15 mL.
10. Sampling and Handling
7.2 Bottles or Flasks, of suitable size equipped with glass
10.1 Sample the material in accordance with Practice
stoppers.
D3437.
7.3 Spectrophotometer or Photometer Cells, with 50 mm to
150 mm light path.
11. Calibration
7.4 Spectrophotometer or Photometer, capable of absor-
11.1 Apparatus—Prepare and operate the spectrophotom-
bance measurements in wavelength region of 420 nm and
eter or photometer in accordance with the manufacturer’s
sensitive to 1 mg polymer/kg monomer.
instructions.
11.2 Reference Standards and Blanks:
8. Reagents and Materials
11.2.1 Dissolve 0.0905 g of polystyrene in 1000 mL of
8.1 Purity of Reagents—Reagent grade chemicals shall be
toluene measured at 25 °C, which is equivalent to 100 mg/kg
used in all tests. Unless otherwise indicated, it is intended that
of polymer in monomer. This serves as the standard for
all reagents shall conform to the specifications of the Commit-
polymer in styrene.
tee on Analytical Reagents of the American Chemical Society,
11.2.2 Make standard solutions containing (1, 3, 6, 9, 12,
where such specifications are available. Other grades may be
15) mg/kg of styrene polymer by diluting (1, 3, 6, 9, 12, 15)
used provided it is first ascertained that the reagent is of
mL of the 100 mg/kg standard solution to 100 mL with toluene
sufficiently high purity to permit its use without lessening the
in a volumetric flask at 25 °C.
accuracy of the determination.
11.3 Calibration Curves and Tables:
8.2 Hexane, dry (CAS 110-54-3).
11.3.1 Into each of a series of bottles equipped with glass
8.3 Methanol, dry (CAS 64-56-1).
stoppers pipet 15 mL of dry methanol and 10 mL of a polymer
standard and mix thoroughly. Into another series of bottles
8.4 Polystyrene (CAS 9003-53-6):
pipet 15 mL of hexane and 10 mL of each polymer standard
and mix thoroughly. Other volumes may be used, depending on
the capacity of the spectrophotometer cell as long as the 3:2
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
Standard-Grade Reference Materials, American Chemical Society, Washington,
proportion is maintained.
DC. For suggestions on the tes
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D2121 − 16 D2121 − 23
Standard Test Methods for
Polymer Content of Styrene Monomer
This standard is issued under the fixed designation D2121; 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 These test methods cover the determination of the polymer content of styrene monomer. It should be noted, however, that
dimers and trimers are not measured by these test methods.
1.2 Test Method A, which is based on the use of a spectrophotometer or photometer, is intended for the quantitative determination
of the polymer content of styrene monomer in concentrations up to 15 mg/kg. Samples containing more than 15 mg/kg of polymer
must be suitably diluted before measurement. The limit of detection (LOD) is 1.2 mg/kg and the limit of quantitation (LOQ) is
4.0 mg/kg. LOD and LOQ were calculated using the last sample in Table 1.
1.3 Test Method B is a rapid visual procedure that is intended for the approximate evaluation of polymer to a maximum
concentration of 1.0 mass %. Samples having a polymer content of 1.0 mass % or greater should be suitably diluted prior to
measurement.
1.4 In determining the conformance of the test results using this method to applicable specifications, results shall be rounded off
in accordance with the rounding-off method of Practice E29.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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 healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use. use. For specific hazard statements, see Section 9.
1.7 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.
2. Referenced Documents
2.1 ASTM Standards:
D2827 Specification for Styrene Monomer
D3437 Practice for Sampling and Handling Liquid Cyclic Products
D4790 Terminology of Aromatic Hydrocarbons and Related Chemicals
D6809 Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related Materials
These test methods are under the jurisdiction of ASTM Committee D16 on Aromatic Hydrocarbons Aromatic, Industrial, Specialty and Related Chemicals and are the
direct responsibility of Subcommittee D16.07 on Styrene, Ethylbenzene and C9 and C10 Aromatic Hydrocarbons.
Current edition approved June 1, 2016Nov. 1, 2023. Published July 2016November 2023. Originally approved in 1962. Last previous edition approved in 20152016 as
D2121 – 15.D2121 – 16. DOI: 10.1520/D2121-16.10.1520/D2121-23.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2121 − 23
TABLE 1 Styrene (mg/kg)
A
Repeatability Reproducibility
Average
Material Limit Limit
¯
r R
X
Sample 1 — 0.4 mg/kg 1.673 1.796 2.827
Sample 2 — 2 mg/kg 2.413 1.711 3.792
Sample 3 — 4 mg/kg 3.759 4.268 5.090
Sample 4 — 10 mg/kg 10.143 3.254 9.037
TABLE 1 Styrene (mg/kg)
A Repeatability Reproducibility
Average
Material Limit Limit
¯
r R
X
Sample 1 — 2 mg/kg 2.6 0.3 0.7
Sample 2 — 5 mg/kg 4.1 0.7 1.3
Sample 3 — 6 mg/kg 7.7 1.1 3.4
A
The average of the laboratories’ calculated averages.
TABLE 2 % Recovery
Average
A
Average
Material Recovery
(mg/kg)
(%)
Sample 1 — 0.4 mg/kg 1.673 418.2
Sample 2 — 2 mg/kg 2.413 120.6
Sample 3 — 4 mg/kg 3.759 94.0
Sample 4 — 10 mg/kg 10.143 101.4
A
The average of the laboratories’ calculated averages.
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 Other Document:
OSHA Regulations, 29CFR paragraphs 1910.1000 and 1910.1200
3. Terminology
3.1 See Terminology D4790 for definition of terms used in this test method.
TEST METHOD A—DETERMINATION OF POLYMER IN STYRENE MONOMER
PHOTOMETERSPECTROSCOPIC METHOD
4. Summary of Test Method
4.1 This test method utilizes the fact that polymers present in the monomers are insoluble in methanol. The polymer content of
styrene monomer is determined by measurement of the degree of turbidity produced by the addition of dry methanol to the styrene
sample.
5. Significance and Use
5.1 This test method can be used for determining polymer concentrations in styrene monomer.
5.2 This test method will not detect dimers and trimers.
5.3 This test method can be used for plant control and for specification analysis.
6. Interferences
6.1 Small changes in turbidity may occur with time. It is, therefore, important that the absorbance of calibration mixtures and
samples be determined after standing the same length of time.
Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http://
www.access.gpo.gov.
D2121 − 23
6.2 Hexane is used for two reasons:
6.2.1 To block out any color in the styrene, and
6.2.2 To indicate dissolved water in the styrene.
7. Apparatus
7.1 Pipets, 10 and 15-mL.10 mL and 15 mL.
7.2 Bottles or Flasks, of suitable size equipped with glass stoppers.
7.3 Spectrophotometer or Photometer Cells, with 50 to 150-mm50 mm to 150 mm light path.
7.4 Spectrophotometer or Photometer, capable of absorbance measurements in wavelength region of 420 nm and sensitive to 1
mg polymer/kg monomer.
8. Reagents and Materials
8.1 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 Committee 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.
8.2 Hexane, dry.dry (CAS 110-54-3).
8.3 Methanol, dry.dry (CAS 64-56-1).
8.4 Polystyrene: Polystyrene (CAS 9003-53-6):
8.4.1 Prepare polystyrene as follows: wash 50 mL of styrene monomer twice with equal volumes of 1 N NaOH solution and twice
with equal volumes of water. After the second water wash, filter the styrene through two layers of rapid filtering ready folded filter
paper. Pour about 20 mL of this styrene monomer into a test tube and heat in an oven at 100°C100 °C for 24 h to promote
polymerization. At the end of this time, remove the polystyrene from the test tube by breaking the tube and discarding all glass.
Grind the polymer plug to a fine powder in an agate mortar.
8.4.2 Commercially available high-purity polystyrene pellets can be used; however, high-molecular weight polystyrene (>150 000
molecular weight) should be specified.
8.5 Styrene Monomer, conforming to Specification D2827. (CAS 100-42-5).
8.6 Toluene, dry.dry (CAS 108-88-3).
9. Hazards
9.1 Styrene monomer is flammable and polymerizes exothermically on contact with peroxides, mineral acids and aluminum
chloride.
9.2 Styrene monomer both in liquid and vapor state, when in sufficient concentrations, acts as an irritant to the eyes and respiratory
tract.
Reagent Chemicals, American Chemical Society Specifications,ACS Reagent Chemicals, Specifications and Procedures for Reagents and Standard-Grade Reference
Materials, 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.
D2121 − 23
9.3 Consult current OSHA regulations, local regulations, and suppliers’ Safety Data Sheets for all materials used in these test
methods.
10. Sampling and Handling
10.1 Sample the material in accordance with Practice D3437.
11. Calibration
11.1 Apparatus—Prepare and operate the spectrophotometer or photometer in accordance with the manufacturer’s instructions.
11.2 Reference Standards and Blanks:
11.2.1 Dissolve 0.0905 g of polystyrene in 1000 mL of toluene measured at 25°C,25 °C, which is equivalent to 100 mg/kg of
polymer in monomer. This serves as the standard for polymer in styrene.
11.2.2 Make standard solutions containing 1,(1, 3, 6, 9, 12, and 15 15) mg/kg of styrene polymer by diluting 1,(1, 3, 6, 9, 12, and
15 15) mL of the 100 mg/kg standard solution to 100 mL with toluene in a volumetric flask at 25°C.25 °C.
11.3 Calibration Curves and Tables:
11.3.1 Into each of a series of bottles equipped with glass stoppers pipet 15 mL of dry methanol and 10 mL of a polymer standard
and mix thoroughly.
...