ASTM D5523-21

Standard Test Method for Polyurethane Raw Materials: Acidity by Argentometric Determination of Hydrolyzable Chlorine in Monomeric, Aromatic Isocyanates

SIGNIFICANCE AND USE
5.1 This test method is suitable for research or for quality control to characterize TDI and MDI.  
5.2 This test method was developed to overcome problems with low-level acidity determinations that use glass electrodes in the presence of reagent alcohol solvents. Reagent alcohols contain acidic and basic species, which complicate the glass electrode methods at low levels of acidity.
SCOPE
1.1 This test method measures the hydrolyzable chlorine content of monomeric, aromatic isocyanates used as polyurethane raw materials and expresses it as HCl acidity. The test method is applicable to toluene diisocyanate (TDI) and monomeric methylene di(phenylisocyanate), known as MDI. The main sources of hydrolyzable chlorine and, therefore, acidity in monomeric aromatic isocyanates are carbamyl chlorides, acid chlorides, and dissolved phosgene. All of these compounds react with alcohols and water to form hydrochloric acid.  
1.2 This test method applies only to monomeric isocyanates in which all of the acidity is derived from species that generate HCl on solvolysis.  
1.3 The values stated in SI units are to be regarded as the standard.  
1.4 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.  
1.5 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-Jan-2021
• ICS: 83.080.20 - Thermoplastic materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.22 - Cellular Materials - Plastics and Elastomers

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: D5523 − 21
Standard Test Method for
Polyurethane Raw Materials: Acidity by Argentometric
Determination of Hydrolyzable Chlorine in Monomeric,
1
Aromatic Isocyanates
This standard is issued under the fixed designation D5523; 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* E456 Terminology Relating to Quality and Statistics
E2935 Practice for Conducting Equivalence Tests for Com-
1.1 This test method measures the hydrolyzable chlorine
paring Testing Processes
content of monomeric, aromatic isocyanates used as polyure-
thane raw materials and expresses it as HCl acidity. The test
3. Terminology
method is applicable to toluene diisocyanate (TDI) and mono-
meric methylene di(phenylisocyanate), known as MDI. The
3.1 Definitions—Terms used in this standard are defined in
mainsourcesofhydrolyzablechlorineand,therefore,acidityin
accordance with Terminology D883, unless otherwise speci-
monomeric aromatic isocyanates are carbamyl chlorides, acid
fied. For terms relating to precision and bias and associated
chlorides, and dissolved phosgene. All of these compounds
issues,thetermsusedinthisstandardaredefinedinaccordance
react with alcohols and water to form hydrochloric acid.
with Terminology E456.
1.2 This test method applies only to monomeric isocyanates
3.2 Definitions of Terms Specific to This Standard:
in which all of the acidity is derived from species that generate
3.2.1 acidity—the acid strength of a sample expressed as
HCl on solvolysis.
parts per million hydrochloric acid (HCl) present.
1.3 The values stated in SI units are to be regarded as the
3.2.2 hydrolyzable chlorine—the amount of chlorine re-
standard.
leased as chloride ion under the conditions of the test,
expressed as parts per million chlorine.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4.1 The sample reacts with 2-propanol to form urethanes
mine the applicability of regulatory limitations prior to use.
and hydrochloric acid, which is liberated from the labile
carbamyl chlorides, acid chlorides, and dissolved phosgene.
NOTE 1—There is no known ISO equivalent to this standard.
The chlorides of the liberated acid are then determined
1.5 This international standard was developed in accor-
potentiometrically using standard methanolic silver nitrate
dance with internationally recognized principles on standard-
solution and calculated as parts per million HCl.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
5. Significance and Use
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
5.1 This test method is suitable for research or for quality
control to characterize TDI and MDI.
2. Referenced Documents
2 5.2 This test method was developed to overcome problems
2.1 ASTM Standards:
with low-level acidity determinations that use glass electrodes
D883 Terminology Relating to Plastics
in the presence of reagent alcohol solvents. Reagent alcohols
contain acidic and basic species, which complicate the glass
1
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
electrode methods at low levels of acidity.
and is the direct responsibility of Subcommittee D20.22 on Cellular Materials -
Plastics and Elastomers.
Current edition approved Jan. 15, 2021. Published January 2021. Originally
6. Interferences
approved in 1994. Last previous edition approved in 2015 as D5523 - 15. DOI:
10.1520/D5523-21.
6.1 Acidic species that do not generate chloride ions under
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
the conditions of this test method will not be determined
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
because acidity is determined indirectly from the chloride ion
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. concentration.
*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
1

---------------------- Page: 1 ----------------------
D5523 − 21
6.2 Acidic species that do not produce chloride ions are Dii
...

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: D5523 − 15 D5523 − 21
Standard Test Method for
Polyurethane Raw Materials: Acidity by Argentometric
Determination of Hydrolyzable Chlorine in Monomeric,
1
Aromatic Isocyanates
This standard is issued under the fixed designation D5523; 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 hydrolyzable chlorine content of monomeric, aromatic isocyanates used as polyurethane raw
materials and expresses it as HCl acidity. The test method is applicable to toluene diisocyanate (TDI) and monomeric methylene
di(phenylisocyanate), known as MDI. The main sources of hydrolyzable chlorine and, therefore, acidity in monomeric aromatic
isocyanates are carbamyl chlorides, acid chlorides, and dissolved phosgene. All of these compounds react with alcohols and water
to form hydrochloric acid.
1.2 This test method applies only to monomeric isocyanates in which all of the acidity is derived from species that generate HCl
on solvolysis.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 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.
1.5 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
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
E456 Terminology Relating to Quality and Statistics
E2935 Practice for Conducting Equivalence Tests for Comparing Testing Processes
1
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, 2015Jan. 15, 2021. Published May 2015January 2021. Originally approved in 1994. Last previous edition approved in 20102015 as
D5523 - 10.D5523 - 15. DOI: 10.1520/D5523-15.10.1520/D5523-21.
2
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
1

---------------------- Page: 1 ----------------------
D5523 − 21
3. Terminology
3.1 Definitions—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.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 acidity—the acid strength of a sample expressed as parts per million hydrochloric acid (HCl) present.
3.2.2 hydrolyzable chlorine—the amount of chlorine released as chloride ion under the conditions of the test, expressed as parts
per million chlorine.
4. Summary of Test Method
4.1 The sample reacts with 2-propanol to form urethanes and hydrochloric acid, which is liberated from the labile carbamyl
chlorides, acid chlorides, and dissolved phosgene. The chlorides of the liberated acid are then determined potentiometrically using
standard methanolic silver nitrate solution and calculated as parts per million HCl.
5. Significance and Use
5.1 This test method is suitable for research or for quality control to characterize TDI and MDI.
5.2 This test method was developed to overcome problems with low-level acidity determinations that use glass electrodes in the
presence of reagent alcohol solvents. Reagent alcohols contain acidic and basic species, which complicate the glass electrode
methods at low levels of acidity.
6. Interferences
6.1 Acidic specie
...