ASTM D7252-22

Standard Test Method for Polyurethane Raw Materials: Determination of Monomer and Isomers in Isocyanates

SIGNIFICANCE AND USE
5.1 This test method is used for research or for quality control to characterize isocyanates used in polyurethane products.
SCOPE
1.1 This test method determines the percent by weight of monomeric isomers and total monomer in crude or modified isocyanates. The test method is applicable to methylene di(phenylisocyanate) (MDI) and polymeric (methylene phenylisocyanate) (PMDI). (See Note 1.)  
1.2 Units—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.
Note 1: There is no known ISO equivalent to this standard.  
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-Jun-2022
• ICS: 19.020 - Test conditions and procedures in general
• ICS: 83.040.01 - Raw materials for rubber and plastics in general
• ICS: 83.100 - Cellular materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

Relations

• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM E682-92(2019) - Standard Practice for Liquid Chromatography Terms and Relationships
• Effective Date: 01-Sep-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E2935-17 - Standard Practice for Conducting Equivalence Testing in Laboratory Applications
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM D883-17 - Standard Terminology Relating to Plastics
• Effective Date: 15-Aug-2017
• Refers: ASTM E2935-16 - Standard Practice for Conducting Equivalence Testing in Laboratory Applications
• Effective Date: 15-Nov-2016

Overview

ASTM D7252-22, titled Standard Test Method for Polyurethane Raw Materials: Determination of Monomer and Isomers in Isocyanates, establishes a laboratory procedure for determining the percentage by weight of monomeric isomers and total monomer in crude or modified isocyanates. This method is particularly applicable to methylene di(phenylisocyanate) (MDI) and polymeric MDI (PMDI), which are commonly used in the production of polyurethane materials.

This standard is utilized extensively in both research and quality control environments, providing essential data for characterizing isocyanate raw materials. The reliable identification of isocyanate monomers and isomers is crucial for ensuring performance, consistency, and safety in polyurethane manufacturing. ASTM D7252-22 is internationally recognized and was developed in line with World Trade Organization Technical Barriers to Trade (TBT) principles.

Key Topics

• Analytical Method: The standard outlines a test procedure based on derivatization with methanol, followed by separation of isomeric derivatives via high performance liquid chromatography (HPLC). This process enables precise quantification of various isocyanate isomers in raw materials.
• Sample Handling: Special precautions are detailed for sampling isocyanates, as these react readily with atmospheric moisture, which can compromise sample integrity.
• Instrumental Parameters: The standard provides typical HPLC settings and recommendations to ensure adequate separation and sensitivity for MDI and PMDI analysis.
• Calibration: Guidance is given for the preparation and use of primary standards comprising known isomer content, including collaborative agreement between laboratories and clients for appropriate reference materials.
• Data Reporting: The method specifies reporting requirements for weight percent of each isomer and overall monomer content to the nearest 0.1%, aiding in comprehensive quality documentation.
• Health and Safety: The document highlights substantial health risks associated with diisocyanate exposure and provides instructions for safe handling, including protective measures during sampling and analysis.

Applications

ASTM D7252-22 is vital in industries where polyurethane chemistry is central, such as:

• Polyurethane Manufacturing: Ensuring raw material quality and performance consistency by monitoring isocyanate monomer and isomer composition.
• Quality Assurance Laboratories: Supporting compliance with internal specifications and regulatory requirements for isocyanate content in bulk materials, intermediate products, and finished goods.
• Research and Development: Characterizing new isocyanate formulations and understanding their impact on final polyurethane product properties.
• Supplier and Customer Agreements: Providing a common analytical platform for verifying material composition as part of supplier-customer quality transactions.

The standard enhances product quality, regulatory compliance, and workplace safety by enabling accurate assessment of potentially hazardous isocyanate constituents.

Related Standards

ASTM D7252-22 makes reference to and aligns with several supporting ASTM standards, including:

• ASTM D883: Terminology Relating to Plastics
• ASTM E456: Terminology Relating to Quality and Statistics
• ASTM E682: Practice for Liquid Chromatography Terms and Relationships
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• ASTM E2935: Practice for Evaluating Equivalence of Two Testing Processes

Notably, there is no known ISO equivalent to this standard, making ASTM D7252-22 a definitive reference for isocyanate analysis in polyurethane applications.

Keywords: isocyanate analysis, MDI, PMDI, polyurethane raw materials, HPLC, isocyanate monomer, isomer determination, ASTM D7252-22, quality control, laboratory method, polymer analysis.

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: D7252 − 22
Standard Test Method for
Polyurethane Raw Materials: Determination of Monomer and
Isomers in Isocyanates
This standard is issued under the fixed designation D7252; 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* 3. Terminology
1.1 This test method determines the percent by weight of 3.1 For definitions of terms used in these test methods see
monomeric isomers and total monomer in crude or modified Terminology D883, unless otherwise specified. For terms
isocyanates.Thetestmethodisapplicabletomethylenedi(phe- relating to precision and bias and associated issues, the terms
nylisocyanate)(MDI)andpolymeric(methylenephenylisocya- used in this standard are defined in accordance with Terminol-
nate) (PMDI). (See Note 1.) ogy E456.
1.2 Units—The values stated in SI units are to be regarded
4. Summary of Test Method
as standard. No other units of measurement are included in this
4.1 The sample is reacted (derivatized) with methanol to
standard.
form a mixture of methyl urethanes. The urethanes mixture is
1.3 This standard does not purport to address all of the
then separated by normal phase high performance liquid
safety concerns, if any, associated with its use. It is the
chromatography (HPLC). The separated, derivatized isomers
responsibility of the user of this standard to establish appro-
are quantified through the use of an internal standard.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
5. Significance and Use
NOTE 1—There is no known ISO equivalent to this standard.
5.1 This test method is used for research or for quality
1.4 This international standard was developed in accor-
control to characterize isocyanates used in polyurethane prod-
dance with internationally recognized principles on standard-
ucts.
ization established in the Decision on Principles for the
6. Apparatus
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
6.1 High Performance Liquid Chromatograph, consisting
Barriers to Trade (TBT) Committee.
of:
6.1.1 Binary (or greater) solvent pump, capable of main-
2. Referenced Documents
taining a pulse-free flow rate of 1-3 milliliters per minute
2.1 ASTM Standards:
6.1.2 Sample injector, automatic or manual, capable of
D883 Terminology Relating to Plastics
reproducibly injecting a 2 microliter volume
E456 Terminology Relating to Quality and Statistics
6.1.3 Column heater, capable of maintaining a temperature
E682 Practice for Liquid Chromatography Terms and Rela-
of 30 6 0.2°C
tionships
6.1.4 UV detector, capable of measurements at 235 nm.
E691 Practice for Conducting an Interlaboratory Study to
6.1.5 Chart recorder or Data system, capable of peak area
Determine the Precision of a Test Method
integration.
E2935 Practice for Evaluating Equivalence of Two Testing
6.2 HPLC analytical column, 250 mm by 4.6 mm by 5 µm
Processes
cyano stationary phase.
1 NOTE 2—Other chromatographic columns are used provided it is
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
ascertained that similar chromatographic performance is obtained.
and is the direct responsibility of Subcommittee D20.22 on Cellular Materials -
Plastics and Elastomers.
6.3 Magnetic Stirring Hotplate.
Current edition approved July 1, 2022. Published July 2022. Originally approved
in 2006. Last previous edition approved in 2017 as D7252 - 17. DOI:10.1520/
7. Reagents and Materials
D7252-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
7.1 Purity of Reagents—Reagent-grade chemicals are to be
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
used in all tests. Unless otherwise indicated, it is intended that
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. all reagents conform to the specifications of the Committee on
*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
D7252 − 22
Analytical Reagents of theAmerican Chemical Society, where column to avoid interference with subsequent analyses. A
such specifications are available. Other grades are used, solvent program such as the one below is used for analysis and
provided it is first ascertained that the reagent is of sufficiently cleanup:
high purity to permit its use without lessening the accuracy of (1)Initial
the determination. Eluent A = 90 %
7.1.1 Acetanilide, 99.9 % purity, to be used as an internal Eluent B = 10 %
standard. Hold for 15 minutes.
7.1.2 Acetonitrile, dry. Dry this and reagents below over (2)Column Flush
molecular sieve for twenty-four hours. EluentA=0%
7.1.3 Ethanol, dry. Use of ethanol denatured with methanol Eluent B = 100 %
(such as SDA-30) is used if more readily available. Hold for 10 minutes.
7.1.4 Hexane, dry. (3)Re-equilibration
7.1.5 Methanol, dry. Eluent A = 90 %
7.1.6 Eluent solution, Mix 1:1 by volume of dry methanol Eluent B = 10 %
and ethanol. Hold for 2.5 minutes
7.1.7 Internal Standard and derivatization solution, Dis-
11. Calibration and Standardization
solve 0.20 g of acetanilide in 1 L of dry methanol.
11.1 The primary standard consists of monomeric material
8. Hazards
of sufficient purity and containing all isomers of interest. The
8.1 Warning—Diisocyanates are eye, skin and respiratory
concentrations of the isomers in the standard are to be in the
irritants at concentrations above the occupational exposure
same ranges as those expected in samples to be analyzed.
limit (TLV or PEL). Diisocyanates can cause skin and respi-
Becauseofthedifficultyinobtainingprimarystandardsforthis
ratory sensitization (asthma) in some people. Once sensitized,
test, agreement on the standard material to be used in testing
it is essential to limit further exposure to diisocyanates. Use a
must be obtained between the testing laboratory and the
combination of engineering controls and personal protective
recipient of the final test results. Several strategies in obtaining
equipment, including respiratory, skin and eye protection, to
suitable standard material have been used.
prevent over-exposure to diisocyanates. Consult the product
11.1.1 Several isomer blends of suitable purity are available
suppliers’Safety Data Sheet (SDS) for more detailed informa-
from several isocyanate manufacturers. These blends are com-
tion about potential health effects and other specific safety and
bined to produce a primary standard with isomers in the same
handling instructions for the product.
range as the samples.
11.1.2 Alternatively, monomer of suitable purity consisting
9. Sampling
of unknown quantities of the isomers of interest is analyzed by
9.1 Since organic isocyanates react with atmospheric
gas chromatography with a flame ionization detector. An area
moisture, take special precautions in sampling. Usual sampling
percenttechniqueisemployedtodeterminetheisomercontent.
methods, even when conducted rapidly, can cause contamina-
Again, agreement between the testing laboratory and the
tion of the sample with insoluble urea. Therefore, blanket the
recipient of the final test results must be obtained for the
sample with dry air or nitrogen at all times. (Warning—see
specific conditions of the gas chromatographic determination.
Section 8, Hazards, for handling concerns.)
11.2 Regardless of which of the strategies above is used, the
10. Instrument Preparation
primary standard is prepared and analyzed as described in the
following sections.
10.1 The instrument settings here are to be used as a guide
forlaboratoryspecificinstrument-columncombinations,which
12. Procedure
are to be adjusted to provide adequate separation and sensitiv-
ity as described in Practice E682.
12.1 Sample Preparation
10.1.1 Pump 12.1.1 Weigh the sample to be analyzed in a 250 mLbeaker.
Flow = 1.5 mL/min Use the formula below to determine the correct weight. Record
Eluent A (hexane) = 90 %
actual weight to the nearest 0.1 milligram.
Eluent B (1:1 by volume ethanol:methanol) = 10 %
10.1.2 Detector Weightofsample ~milligrams! 5
Expectedwt% monomerinsample
Wavelength = 235 nm
(1)
Output Range = 2.000 au full scale
10.1.3 Additional Settings 12.1.2 Dissolve the sample in 20 mLof dry acetonitrile and
Injection volume=2µL add exactly 100 mL of the (Internal Standard and derivatiza-
Column Temperature = 30°C tion) solution. Add a stirring bar, cover with watch glass and
Stop Time = 25 minutes heat on hotplate/stirrer for fifteen
...

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: D7252 − 17 D7252 − 22
Standard Test Method for
Polyurethane Raw Materials: Determination of Monomer and
Isomers in Isocyanates
This standard is issued under the fixed designation D7252; 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 Scope*
1.1 This test method determines the percent by weight of monomeric isomers and total monomer in crude or modified isocyanates.
The test method is applicable to methylene di(phenylisocyanate) (MDI) and polymeric (methylene phenylisocyanate) (PMDI). (See
Note 1.)
1.2 Units—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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
NOTE 1—There is no known ISO equivalent to this standard.
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.
2. Referenced Documents
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
E456 Terminology Relating to Quality and Statistics
E682 Practice for Liquid Chromatography Terms and Relationships
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E2935 Practice for Evaluating Equivalence of Two Testing Processes
3. Terminology
3.1 For definitions of terms used in these test methods see Terminology D883, unless otherwise specified. For terms relating to
precision and bias and associated issues, the terms used in this standard are defined in accordance with Terminology E456.
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plastics
and Elastomers.
Current edition approved April 15, 2017July 1, 2022. Published May 2017July 2022. Originally approved in 2006. Last previous edition approved in 20112017 as
ɛ1
D7252 - 06D7252 - 17.(2011) . DOI:10.1520/D7252-17. DOI:10.1520/D7252-22.
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
D7252 − 22
4. Summary of Test Method
4.1 The sample is reacted (derivatized) with methanol to form a mixture of methyl urethanes. The urethanes mixture is then
separated by normal phase high performance liquid chromatography (HPLC). The separated, derivatized isomers are quantified
through the use of an internal standard.
5. Significance and Use
5.1 This test method is used for research or for quality control to characterize isocyanates used in polyurethane products.
6. Apparatus
6.1 High Performance Liquid Chromatograph, consisting of:
6.1.1 Binary (or greater) solvent pump, capable of maintaining a pulse-free flow rate of 1-3 milliliters per minute
6.1.2 Sample injector, automatic or manual, capable of reproducibly injecting a 2 microliter volume
6.1.3 Column heater, capable of maintaining a temperature of 30 6 0.2°C
6.1.4 UV detector, capable of measurements at 235 nm.
6.1.5 Chart recorder or Data system, capable of peak area integration.
6.2 HPLC analytical column, 250 mm by 4.6 mm by 5 μm cyano stationary phase.
NOTE 2—Other chromatographic columns are used provided it is ascertained that similar chromatographic performance is obtained.
6.3 Magnetic Stirring Hotplate.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent-grade chemicals are to be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such
specifications are available. Other grades are 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.
7.1.1 Acetanilide, 99.9 % purity, to be used as an internal standard.
7.1.2 Acetonitrile, dry. Dry this and reagents below over molecular sieve for twenty-four hours.
7.1.3 Ethanol, dry. Use of ethanol denatured with methanol (such as SDA-30) is used if more readily available.
7.1.4 Hexane, dry.
7.1.5 Methanol, dry.
7.1.6 Eluent solution, Mix 1:1 by volume of dry methanol and ethanol.
7.1.7 Internal Standard and derivatization solution, Dissolve 0.20 g of acetanilide in 1 L of dry methanol.
8. Hazards
8.1 Warning—Diisocyanates are eye, skin and respiratory irritants at concentrations above the occupational exposure limit (TLV
or PEL). Diisocyanates can cause skin and respiratory sensitization (asthma) in some people. Once sensitized, it is essential to limit
further exposure to diisocyanates. Use a combination of engineering controls and personal protective equipment, including
D7252 − 22
respiratory, skin and eye protection, to prevent over-exposure to diisocyanates. Consult the product suppliers’ Safety Data Sheet
(SDS) for more detailed information about potential health effects and other specific safety and handling instructions for the
product.
9. Sampling
9.1 Since organic isocyanates react with atmospheric moisture, take special precautions in sampling. Usual sampling methods,
even when conducted rapidly, can cause contamination of the sample with insoluble urea. Therefore, blanket the sample with dry
air or nitrogen at all times. (Warning— Diisocyanates are eye, skin and respiratory irritants at concentrations above the
occupational exposure limit (TLV or PEL). Diisocyanates can cause skin and respiratory sensitization (asthma) in some people.
Once sensitized, it is essential to limit further exposure to diisocyanates. Use a combination of engineering controls and personal
protective equipment, including respiratory, skin and eye protection, to prevent over-exposure to diisocyanates. Consult the product
suppliers’ Safety Data Sheet (SDS) for more detailed information about potential health effects and other specific safety and
handling instructions for the product)Warning—see Section 8, Hazards, for handling concerns.)
10. Instrument Preparation
10.1 The instrument settings here are to be used as a guide for laboratory specific instrument-column combinations, which are to
be adjusted to provide adequate separation and sensitivity as described in Practice E682.
10.1.1 Pump
Flow = 1.5 mL/min
Eluent A (hexane) = 90 %
Eluent B (1:1 by volume ethanol:methanol) = 10 %
10.1.2 Detector
Wavelength = 235 nm
Output Range = 2.000 au full scale
10.1.3 Additional Settings
Injection volume = 2 μL
Column Temperature = 30°C
Stop Time = 25 minutes
Post Run Time = 10 minutes
10.1.4 Solvent Program
10.1.4.1 After the components of interest have eluted, it is desirable to flush the remainder of the material from the column to
avoid interference with subsequent analyses. A solvent program such as the one below is used for analysis and cleanup:
(1) Initial
Eluent A = 90 %
Eluent B = 10 %
Hold for 15 minutes.
(2) Column Flush
Eluent A = 0 %
Eluent B = 100 %
Hold for 10 minutes.
(3) Re-equilibration
Eluent A = 90 %
Eluent B = 10 %
Hold for 2.5 minutes
11. Calibration and Standardization
11.1 The primary standard consists of monomeric material of sufficient purity and containing all isomers of interest. The
concentrations of the isomers in the standard are to be in the same ranges as those expected in samples to be analyzed. Because
of the difficulty in obtaining primary standards for this test, agreement on the standard material to be used in testing must be
obtained between the testing laboratory and the recipient of the final test results. Several strategies in obtaining suitable standard
material have been used.
D7252 − 22
11.1.1 Several isomer blends of suitable purity are available from several isocyanate manufacturers. These blends are combined
to produce a primary standard with isomers in the same range as the samples.
11.1.2 Alternatively, monomer of suitable purity consisting of unknown quantities of the isomers of interest is analyzed by gas
chromatography with a flame ionization detector. An area percent technique is employed to determine the isomer content. Again,
agreement between the testing laboratory and the recipient of the final test results must be obtained for the specific conditions of
the gas chromatographic determination.
11.2 Regardless of which of the strategies above is used, the primary standard is prepared and analyzed as described in the
following sections.
12. Procedure
12.1 Sam
...