ASTM D6437-22

Standard Test Method for Polyurethane Raw Materials: Alkalinity in Low-Alkalinity Polyols (Determination of CPR Values of Polyols)

SIGNIFICANCE AND USE
5.1 This test method is suitable for quality control, as a specification test and for research. The urethane reaction between polyols and isocyanates to form polyurethane polymers is known to be sensitive to the presence of basic substances. This is particularly important in the preparation of polyurethane prepolymers which contain isocyanate groups that are known to react in the presence of trace amounts of basic substances. Since many polyether polyols are often made with strongly basic catalysts, it is important to have an analytical method capable of detecting small quantities of residual basic substances. This test method is capable of detecting ppm levels of base (as KOH).4
SCOPE
1.1 This test method covers measuring alkalinity in low-alkalinity (  
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: 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: 14-Mar-2022
• ICS: 83.040.01 - Raw materials for rubber and plastics in general
• 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 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
• Refers: ASTM E2935-15 - Standard Practice for Conducting Equivalence Testing in Laboratory Applications
• Effective Date: 01-Oct-2015

Overview

ASTM D6437-22: Standard Test Method for Polyurethane Raw Materials: Alkalinity in Low-Alkalinity Polyols (Determination of CPR Values of Polyols) provides a reliable procedure for measuring the alkalinity in low-alkalinity polyols, specifically polyether polyols used in polyurethane production. The presence of basic substances in polyols can significantly impact the urethane reaction, affecting the quality and characteristics of resulting polyurethane products. This ASTM standard is essential for quality control, product specification, and research activities in the polyurethane industry, providing a sensitive approach to detect residual basic substances at the parts-per-million (ppm) level.

Key Topics

• Test Method Applicability:
  • Focuses on low-alkalinity polyether polyols (not applicable to amine-based polyols)
  • Suitable for polyols with basicity below 0.002 meq/g
• Method Summary:
  • Uses potentiometric titration with methanol as a solvent and dilute hydrochloric acid as titrant
  • Able to identify and quantify trace levels of residual basic substances in polyols
• Significance:
  • Ensures the performance, stability, and consistency of polyurethane prepolymers and end-products
  • Establishes product compliance and supports specification requirements
• Units:
  • All measurements follow SI units as standard
• Precision and Repeatability:
  • Results validated through robust interlaboratory studies and described in terms of precision and reproducibility

Applications

The determination of alkalinity in polyether polyols is critical for several practical applications within the polyurethane manufacturing industry:

• Quality Control:

  • Detects ppm levels of basic impurities that could adversely affect the reactivity and quality of polyurethane foams, elastomers, adhesives, and coatings
  • Allows manufacturers to maintain strict product specifications and prevent process variability

• Research and Development:

  • Supports analytical investigations aimed at optimizing polyol formulations and catalyst strategies for improved polymer performance

• Raw Material Assessment:

  • Ensures supplied polyols meet essential purity requirements before entering production lines for isocyanate-based reactions

• Process Monitoring:

  • Facilitates consistent production of high-performance polyurethane products by providing early detection of unwanted basic residues

Related Standards

The use and interpretation of ASTM D6437-22 is supported by other ASTM standards that define terminology, testing precision, and general practice for chemical testing:

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

There is no known ISO equivalent for ASTM D6437-22, highlighting its unique position in the international standards landscape for polyurethane raw materials testing.

Practical Value

Adherence to ASTM D6437-22 enables polyurethane manufacturers and raw material suppliers to confidently assess and manage alkaline impurities in polyether polyols. This, in turn, protects product integrity, enhances reliability, and ensures compliance with industry specifications. By following this standard test method, organizations can achieve consistent polyurethane quality, reduce the risk of unwanted chemical side reactions, and support advanced research in polymer chemistry.

Keywords: alkalinity, basicity, CPR, polyether polyol, polyurethane, prepolymer, quality control, raw materials, titration, ASTM D6437-22

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: D6437 − 22
Standard Test Method for
Polyurethane Raw Materials: Alkalinity in Low-Alkalinity
Polyols (Determination of CPR Values of Polyols)
This standard is issued under the fixed designation D6437; 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* E2935 Practice for Evaluating Equivalence of Two Testing
Processes
1.1 This test method covers measuring alkalinity in low-
alkalinity (<0.002 meq/g basicity) polyols. This alkalinity is
3. Terminology
often expressed as CPR (controlled polymerization rate) of
3.1 Definitions:
polyether polyols. This test method is not applicable to
3.1.1 Terms used in this standard are defined in accordance
amine-based polyols.
with Terminology D883, unless otherwise specified. For terms
1.2 The values stated in SI units are to be regarded as
relating to precision and bias and associated issues, the terms
standard.
used in this standard are defined in accordance with Terminol-
1.3 This standard does not purport to address all of the
ogy E456.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 CPR—controlled polymerization rate is expressed as
priate safety, health, and environmental practices and deter-
basicity in milliequivalents per 30 kg of sample (meq/30 kg).
mine the applicability of regulatory limitations prior to use.
NOTE 1—There is no known ISO equivalent to this standard. 4. Summary of Test Method
1.4 This international standard was developed in accor-
4.1 This test method is a potentiometric titration for sample
dance with internationally recognized principles on standard-
basicity in methanol solvent. This test method uses a relatively
ization established in the Decision on Principles for the
large amount of sample and the titration is performed with
Development of International Standards, Guides and Recom-
dilute acid solution to determine trace quantities of basicity.
mendations issued by the World Trade Organization Technical
5. Significance and Use
Barriers to Trade (TBT) Committee.
5.1 This test method is suitable for quality control, as a
2. Referenced Documents
specification test and for research. The urethane reaction
2.1 ASTM Standards:
between polyols and isocyanates to form polyurethane poly-
D883 Terminology Relating to Plastics
mers is known to be sensitive to the presence of basic
E180 Practice for Determining the Precision of ASTM
substances. This is particularly important in the preparation of
Methods for Analysis and Testing of Industrial and Spe-
polyurethane prepolymers which contain isocyanate groups
cialty Chemicals (Withdrawn 2009)
that are known to react in the presence of trace amounts of
E456 Terminology Relating to Quality and Statistics
basic substances. Since many polyether polyols are often made
E691 Practice for Conducting an Interlaboratory Study to
with strongly basic catalysts, it is important to have an
Determine the Precision of a Test Method
analytical method capable of detecting small quantities of
residual basic substances. This test method is capable of
detecting ppm levels of base (as KOH).
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
and is the direct responsibility of Subcommittee D20.22 on Cellular Materials -
6. Apparatus
Plastics and Elastomers.
Current edition approved March 15, 2022. Published March 2022. Originally
6.1 Potentiometric Automatic Titrator, capable of detecting
ɛ1
approved in 1999. Last previous edition approved in 2016 as D6437 - 05 (2016) .
multiple titration end points.
DOI: 10.1520/D6437-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
6.2 Autotitrator Buret, 5 mL (see Note 2).
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.
3 4
The last approved version of this historical standard is referenced on H.G. Scholten, J.G. Schuhman, R.E. TenHoor, Journal of Chemical Engineer-
www.astm.org. ing Data, 5, 1960, p. 396.
*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
D6437 − 22
6.3 Buret or Dosing Device, capable of dosing 50 mL. 10. Precision and Bias
10.1 Precision—Table 1 is based on a round robin con-
6.4 pH Glass Electrode and Reference Electrode or a
ducted in 1997 in accordance with Practice E691 with the data
Combination Glass Electrode.
analysis in accordance with Practice E180, involving five
6.5 Analytical Balance, capable of weighing to the nearest
samples tested by seven laboratories. Each test result was the
0.01 g.
average of two individual determinations. Each laboratory
made duplicate determinations on each material on each of two
NOTE 2—A1-mLtitrator buret can be used if available. Due to the low
days. (Warning—The following explanations of r and R
volumes of titrant typically required (0 to 0.5 mL), larger burets will give
less precise results.
(10.1.1–10.1.3)areonlyintendedtopresentameaningfulway
of considering the approximate precisio
...

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.
´1
Designation: D6437 − 05 (Reapproved 2016) D6437 − 22
Standard Test Method for
Polyurethane Raw Materials: Alkalinity in Low-Alkalinity
Polyols (Determination of CPR Values of Polyols)
This standard is issued under the fixed designation D6437; 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.
ε NOTE—Reapproved with editorial changes in April 2016.
1. Scope Scope*
1.1 This test method covers measuring alkalinity in low-alkalinity (<0.002 meq/g basicity) polyols. This alkalinity is often
expressed as CPR (controlled polymerization rate) of polyether polyols. This test method is not applicable to amine-based polyols.
1.2 The values stated in SI units are to be regarded as the 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
E180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals
(Withdrawn 2009)
E456 Terminology Relating to Quality and Statistics
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 Definitions:
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 1, 2016March 15, 2022. Published April 2016March 2022. Originally approved in 1999. Last previous edition approved in 20102016 as
ɛ1
D6437 - 05 (2010)(2016) . DOI: 10.1520/D6437-05R16E01.10.1520/D6437-22.
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.
The last approved version of this historical standard is referenced on www.astm.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
D6437 − 22
3.1.1 The terminologyTerms used in this test method isstandard are defined in accordance with Terminology D883the standard
terminology defined in , 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 D883E456.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 CPR—controlled polymerization rate is expressed as basicity in milliequivalents per 30 kg of sample (meq/30 kg).
4. Summary of Test Method
4.1 This test method is a potentiometric titration for sample basicity in methanol solvent. This test method uses a relatively large
amount of sample and the titration is performed with dilute acid solution to determine trace quantities of basicity.
5. Significance and Use
5.1 This test method is suitable for quality control, as a specification test and for research. The urethane reaction between polyols
and isocyanates to form polyurethane polymers is known to be sensitive to the presence of basic substances. This is particularly
important in the preparation of polyurethane prepolymers which contain isocyanate groups that are known to react in the presence
of trace amounts of basic substances. Since many polyether polyols are often made with strongly basic catalysts, it is important
to have an analytical method capable of detecting small quantities of residual basic substances. This test method is capable of
detecting ppm levels of base (as KOH).
6. Apparatus
6.1 Potentiometric Automatic Titrator, capable of detecting multiple titration end points.
6.2 Autotitrator Buret, 5 mL (see Note 2).
6.3 Buret or Dosing Device, capable of dosing 50 mL.
6.4 pH Glass Electrode and Reference Electrode or a Combination Glass Electrode.
6.5 Analytical Balance, capable of weighing to the nearest 0.01 g.
NOTE 2—A 1-mL titrator buret can be used if available. Due to the low volumes of titrant typically required (0 to 0.5 mL), larger burets will give less
precise results.
7. Reagents and Materials
7.1 HCl Aqueous, 0.01 N—Standardize to detect changes of 0.0001 N.
7.2 Methanol, reagent grade
8. Procedure
8.1 Set up the autotitrator to find multiple end points with a maximum volume of 5 mL.
8.2 Place 50 6 0.1 mL of methanol in a 100-mL titration cup and titrate a blank using 0.01 N aqueous HCl.
8.3 Weigh 30 6 1.00 g of sample into a titration cup. Add 50 6 0.1 mL of methanol, stir to mix well, and titrate with 0.01 N
aqueous HCl. There will be as many as three end points (breaks) in these titrations. Use the volume to the last end point for
calculation.
H.G. Scholten, J.G. Schuhman, R.E. TenHoor, Journal of Chemical Engineering Data, 5, 1960, p. 396.
...