ASTM D4877-19

Standard Test Method for Polyurethane Raw Materials: Determination of APHA Color in Isocyanates

SIGNIFICANCE AND USE
5.1 This test method can be used for research or for quality control to characterize isocyanates used in polyurethane products.  
5.2 For toluene diisocyanate, results from this test method can relate to reactivity or performance in polyurethane systems.
SCOPE
1.1 This test method measures the color of clear liquids. It is applicable only to materials whose color-producing bodies have light-absorption characteristics similar to those of the platinum cobalt color standards used.2 (See Test Method D1209 and Note 1.) Suitable isocyanates include toluene diisocyanate, and pure or modified monomeric methylene di(phenylisocyanate).  
1.2 The values stated in SI units are to be regarded as 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: This standard and ISO 6271-1 address the same subject matter, but differ in technical content.  
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: 31-Jul-2019
• ICS: 71.080.30 - Organic nitrogen compounds
• ICS: 83.040.30 - Auxiliary materials and additives for plastics
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

Relations

• Replaces: ASTM D4877-14 - Standard Test Method for Polyurethane Raw Materials: Determination of APHA Color in Isocyanates
• Effective Date: 01-Aug-2019
• 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 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)e3 - 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)e1 - 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 D4877-19: Standard Test Method for Polyurethane Raw Materials: Determination of APHA Color in Isocyanates establishes a procedure to determine the color of clear liquid isocyanates using the APHA (American Public Health Association) or platinum-cobalt (Pt/Co) scale. This color determination is essential in characterizing isocyanates, which are widely used as raw materials in polyurethane production. The method is especially significant for quality control and research, as color can impact reactivity and overall performance in polyurethane systems.

Key Topics

• Scope: The test method is applicable only to clear liquids whose color-producing compounds have light absorption properties similar to those in Pt/Co color standards.
  • Key isocyanates covered include:
    • Toluene diisocyanate (TDI)
    • Pure or modified monomeric methylene di(phenylisocyanate) (MDI)
• Test Principle: The sample’s color is visually compared to a series of calibrated platinum-cobalt color standards. The closest match determines the APHA color number.
• Equipment and Materials: Utilizes matched 100-mL Nessler tubes and platinum-cobalt reference solutions prepared according to standardized procedures.
• Sampling Considerations:
  • Special precautions are necessary because isocyanates react rapidly with atmospheric moisture.
  • Use techniques that minimize exposure to air, such as blanketing samples with dry air or nitrogen.
  • Proper personal protective equipment (PPE) and adherence to safety data sheets (SDS) are mandatory due to potential health hazards associated with isocyanates.
• Reporting: The result is recorded as the color standard number that best matches the sample. If the color is between two standards, the darker standard is reported.

Applications

• Quality Control in Polyurethane Manufacturing: Provides reliable assessment of raw material purity. Unintended color can indicate contamination or process issues that affect polyurethane properties.
• Research and Formulation: Used in development or modification of isocyanate-based products, ensuring consistency and desired outcomes in experimental work.
• Supplier Specifications: Facilitates communication and compliance between raw material suppliers and polyurethane manufacturers by providing an industry-accepted reference for color quality.
• Regulatory Compliance: Offers a standardized approach that supports international trade and meets quality standards recognized by ASTM and ISO.

Related Standards

Understanding ASTM D4877-19’s context is enhanced by reviewing related standards:

• ASTM D1209: Test Method for Color of Clear Liquids (Platinum-Cobalt Scale). The foundational method for preparing color standards used in D4877.
• ASTM D4890: Test Methods for Polyurethane Raw Materials: Determination of Gardner and APHA Color of Polyols. Provides guidance for analyzing other polyurethane raw materials.
• ASTM D5386: Test Method for Color of Liquids Using Tristimulus Colorimetry. An instrumental alternative for color measurements.
• ISO 6271-1: Estimation of color by the platinum-cobalt scale - Part 1: Visual method. Equivalent in subject matter, but with technical differences from ASTM D4877-19.
• ASTM D883 and ASTM E456: For terminology referenced in testing and statistical practices.
• ASTM E2935: Practice for Conducting Equivalence Testing in Laboratory Applications.

Practical Value

Implementing ASTM D4877-19 ensures consistent, repeatable color measurement of isocyanates crucial to polyurethane manufacturing. By adhering to this internationally recognized standard, organizations improve product quality, reduce variability, and meet stakeholder and regulatory expectations. The method’s simplicity and visual nature make it accessible for routine laboratory quality checks, bridging communication between suppliers and end users, and supporting global trade in polyurethane raw materials.

Keywords: ASTM D4877-19, APHA color, isocyanates, polyurethane raw materials, platinum-cobalt scale, Pt/Co scale, quality control, TDI, MDI, ASTM standards, color measurement, polyurethane industry.

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: D4877 − 19
Standard Test Method for
Polyurethane Raw Materials: Determination of APHA Color
in Isocyanates
This standard is issued under the fixed designation D4877; 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* D4890 Test Methods for Polyurethane Raw Materials: De-
termination of Gardner and APHA Color of Polyols
1.1 This test method measures the color of clear liquids. It
D5386 Test Method for Color of Liquids Using Tristimulus
is applicable only to materials whose color-producing bodies
Colorimetry
have light-absorption characteristics similar to those of the
2 E456 Terminology Relating to Quality and Statistics
platinum cobalt color standards used. (See Test Method
E2935 Practice for Conducting Equivalence Testing in
D1209 and Note 1.) Suitable isocyanates include toluene
Laboratory Applications
diisocyanate, and pure or modified monomeric methylene
2.2 ISO Standards:
di(phenylisocyanate).
ISO 6271-1 Clear liquids—Estimation of colour by the
1.2 The values stated in SI units are to be regarded as
platinum-cobalt scale—Part 1: Visual method
standard.
3. Terminology
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 3.1 Terms used in this standard are defined in accordance
with Terminology D883, unless otherwise specified. For terms
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter- relating to precision and bias and associated issues, the terms
used in this standard are defined in accordance with Terminol-
mine the applicability of regulatory limitations prior to use.
ogy E456.
NOTE 1—This standard and ISO 6271-1 address the same subject
matter, but differ in technical content.
4. Summary of Test Method
1.4 This international standard was developed in accor-
4.1 The color of the material to be tested is compared to a
dance with internationally recognized principles on standard-
series of platinum cobalt color standards, designated by mg of
ization established in the Decision on Principles for the
Pt/mLofstandardsolution.Theresultsarereportedasthecolor
Development of International Standards, Guides and Recom-
standard, which best matches the sample (Note 2).
mendations issued by the World Trade Organization Technical
NOTE 2—Test methods for measuring the platinum-cobalt color of
Barriers to Trade (TBT) Committee.
liquids instrumentally are available—for example, Test Method D5386.
2. Referenced Documents
5. Significance and Use
2.1 ASTM Standards:
5.1 This test method can be used for research or for quality
D883 Terminology Relating to Plastics
control to characterize isocyanates used in polyurethane prod-
D1193 Specification for Reagent Water
ucts.
D1209 Test Method for Color of Clear Liquids (Platinum-
5.2 For toluene diisocyanate, results from this test method
Cobalt Scale)
can relate to reactivity or performance in polyurethane sys-
tems.
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
6. Apparatus
and is the direct responsibility of Subcommittee D20.22 on Cellular Materials -
Plastics and Elastomers.
6.1 Nessler Tubes, matched, 100-mL tall-form.
Current edition approved Aug. 1, 2019. Published August 2019. Originally
approved in 1988. Last previous edition approved in 2014 as D4877 - 14. DOI:
7. Reagents and Materials
10.1520/D4877-19.
See Standard Methods for the Examination of Water, Sewage, and Industrial
7.1 Purity of Reagents—Reagent grade chemicals shall be
Wastes, AM. Public Health Assn., 1015 15th St. NW Washington, DC 20005.
used in all tests. Unless otherwise indicated, it is intended that
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 Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
*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
D4877 − 19
TABLE 1 Color Standards
all reagents conform to the specifications of the Committee on
Analytical Reagents of the American Chemical Society where Color Standard Number Number 500 Standard, mL Water, mL
such specifications are available. Other grades are acceptable, 1 0.2 99.8
3 0.6 99.4
provided it is first ascertained that the reagent is of sufficiently
5 1.0 99.0
high purity to permit its use without lessening the accuracy of
10 2.0 98.0
the determination. 15 3.0 97.0
18 3.6 96.4
7.2 Purity of Water—Unless otherwise indicated, references
20 4.0 96.0
25 5.0 95.0
to water shall be understood to mean reagent water as defined
30 6.0 94.0
by Type IV or better of Specification D1193.
40 8.0 92.0
50 10.0 90.0
7.3 Cobalt (II) Chloride Hexahydrate (CoCl ·6H O).
2 2
80 12.0 88.0
70 14.0 86.0
7.4 Concentrated Hydrochloric Acid (sp. gr. 1.19).
80 16.0 84.0
7.5 Potassium Hexachloroplatinate (K PtCl ). 90 18.0 82.0
2 6
100 20.0 80.0
120 24.0 76.0
8. Sampling
140 28.0 72.0
160 32.0 68.0
8.1 Since organic isocyanates react with atmospheric
180 36.0 64.0
moisture, take special precautions in sampling. Usual sampling
200 40.0 60.0
methods, even when conducted rapidly, can cause contamina- 300 60.0 40.0
400 80.0 20.0
tion of the sample with insoluble urea. Therefore, blanket the
500 100.00 0.0
sample with dry air or nitrogen at all times. (Warning—
Diisocyanates are eye, skin and respiratory irritants at concen-
trations above the occupational exposure limit (TLV or PEL).
Diisocyanates can cause skin and respiratory sensitization
metallic platinum/L). When not in use, standards are to be
(asthma)insomepeople.Oncesensitized,itisessen
...

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: D4877 − 14 D4877 − 19
Standard Test Method for
Polyurethane Raw Materials: Determination of APHA Color
in Isocyanates
This standard is issued under the fixed designation D4877; 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 measures the color of clear liquids. It is applicable only to materials whose color-producing bodies have
light-absorption characteristics similar to those of the platinum cobalt color standards used. (See Test Method D1209 and Note
1.) Suitable isocyanates include toluene diisocyanate, and pure or modified monomeric methylene di(phenylisocyanate).
1.2 The values stated in SI units are to be regarded as 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—This standard is equivalent to ISO 6271-1:2004.and ISO 6271-1 address the same subject matter, but differ in technical content.
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
D1193 Specification for Reagent Water
D1209 Test Method for Color of Clear Liquids (Platinum-Cobalt Scale)
D4890 Test Methods for Polyurethane Raw Materials: Determination of Gardner and APHA Color of Polyols
D5386 Test Method for Color of Liquids Using Tristimulus Colorimetry
E456 Terminology Relating to Quality and Statistics
E2935 Practice for Conducting Equivalence Testing in Laboratory Applications
2.2 ISO Standards:
ISO 6271-1:2004 ISO 6271-1 Clear liquids—Estimation of colour by the platinum-cobalt scale—Part 1: Visual method
3. Terminology
3.1 For definitions of terms Terms used in this test method see standard are defined in accordance with 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.
4. Summary of Test Method
4.1 The color of the material to be tested is compared to a series of platinum cobalt color standards, designated by mg of Pt/mL
of standard solution. The results are reported as the color standard, which best matches the sample (Note 2).
NOTE 2—Test methods for measuring the platinum-cobalt color of liquids instrumentally are available—for example, Test Method D5386.
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 Aug. 1, 2014Aug. 1, 2019. Published September 2014August 2019. Originally approved in 1988. Last previous edition approved in 20102014
as D4877 - 10.D4877 - 14. DOI: 10.1520/D4877-14.10.1520/D4877-19.
See Standard Methods for the Examination of Water, Sewage, and Industrial Wastes, AM. Public Health Assn., 1015 15th St. NW Washington, DC 20005.
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.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
*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
D4877 − 19
5. Significance and Use
5.1 This test method can be used for research or for quality control to characterize isocyanates used in polyurethane products.
5.2 For toluene diisocyanate, results from this test method can relate to reactivity or performance in polyurethane systems.
6. Apparatus
6.1 Nessler Tubes, matched, 100-mL tall-form.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent grade chemicals shall 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 can be used, are acceptable, provided it is first ascertained that the reagent is of
sufficiently high purity to permit its use without lessening the accuracy of the determination.
7.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water as defined by
Type IV or better of Specification D1193.
7.3 Cobaltous Cobalt (II) Chloride Hexahydrate (CoCl · 6H O).
2 2
7.4 Concentrated Hydrochloric Acid (sp. gr. 1.19).
7.5 Potassium ChloroplatinateHexachloroplatinate (K PtCl ).
2 6
8. Sampling
8.1 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—Many diisocyanates are known or suspected sensitizers. Over-exposure to diisocyanates
can lead to adverse health effects, which may include the development of occupational asthma and other respiratory, skin, and eye
effects. Engineering controls, or personal protective equipment or both, including respiratory, skin,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, are to be
used when there is a potential for to prevent over-exposure to diisocyanates. The Consult the product suppliers’ Safety Data Sheet
(SDS) providesfor more detailed information about potential adverse health effects and other importantspecific safety and handling
information. Always follow the specific instructions provided on the SDS.instructions for the product.)
9. Preparation of Color Standards (See Note 3)
9.1 Add 500 mL distilled water to a 1000-mL volumetric flask. Add 100 mL HCl and mix well. Weigh 1.245 g of K PtCl to
2 6
the nearest 1 mg and transfer it to the volumetric flask. Add 1.00 g of crystallized CoCl · 6H O. Dilute th
...