ISO 14897:2023

Plastics - Polyols for use in the production of polyurethanes - Determination of water content

This document specifies methods used to measure the water content of polyols employed as polyurethane raw materials. Method A is a manual amperometric method which has been included to better define the principles of the Karl Fischer measurement. Amperometric methods are applicable to a wide range of polyols, including those which have enough colour to obscure a visual end-point. Method B includes an automated amperometric procedure and an automated coulometric procedure. The coulometric procedure is an absolute method that does not require calibration and gives improved sensitivity compared with amperometric methods.

Plastiques — Polyols destinés à la production de polyuréthanes — Dosage de l'eau

General Information

• Status: Published
• Publication Date: 21-Jun-2023
• ICS: 83.080.10 - Thermosetting materials
• Technical Committee: ISO/TC 61/SC 12 - Thermosetting materials
• Drafting Committee: ISO/TC 61/SC 12 - Thermosetting materials
• Current Stage: 6060 - International Standard published
• Start Date: 22-Jun-2023
• Due Date: 14-Mar-2024
• Completion Date: 22-Jun-2023

Relations

• Revises: ISO 14897:2002 - Plastics - Polyols for use in the production of polyurethane - Determination of water content
• Effective Date: 17-Sep-2022

Overview

ISO 14897:2023 specifies laboratory methods for the determination of water content in polyols used as raw materials for the production of polyurethanes. The standard describes two main approaches based on Karl Fischer titration:

• Method A - a manual amperometric titration (included to clarify Karl Fischer principles), and
• Method B - automated amperometric and coulometric titrations.

The coulometric procedure is an absolute method (no calibration required) and offers improved sensitivity compared with amperometric techniques. The standard is intended for quality control, specification testing and research in polyurethane production.

Key topics and technical requirements

• Measurement principles: Karl Fischer reaction (iodine/sulfur dioxide system) and detection by amperometry or coulometry.
• Method scope: Applicable to a wide range of polyether polyols, including colored polyols where visual end-points are obscured.
• Reagents and purity: Reagent-grade chemicals and grade 3 water (ISO 3696) are required. Recommendations include pyridine-free Karl Fischer reagents and guidance on preparing titration solvents. Typical reagent strength guidance is provided (e.g., ~2.5–3.5 mg H2O/ml for Method A).
• Apparatus and instrumentation: Manual titration vessel, platinum electrodes and depolarization indicator for Method A; commercial autotitrators and appropriate reagent systems for Method B.
• Interferences and sample suitability: Oxides, hydroxides and strong bases produce water-like artifacts (can give falsely high results). Amine-containing polyols can shift pH and require mitigation (e.g., addition of salicylic or benzoic acid).
• Procedure, calibration and calculation: Standardization procedures for amperometric titrants and the note that coulometric titration is absolute (no external titrant standardization).
• Precision, bias and reporting: Sections on method precision, bias and required test report content; interlaboratory study data provided in informative annex.

Applications and users

• Who uses it: Analytical laboratories, polyurethane raw-material manufacturers, QC/QA teams, R&D scientists, and regulatory/compliance units.
• Practical applications:
  • Incoming raw-material inspection (polyol batches)
  • In-process monitoring to prevent isocyanate consumption by water (avoiding CO2 generation and foam defects)
  • Specification testing for product release and supplier qualification
  • Research into formulation stability and moisture control

Related standards

• ISO 3696 - Water for analytical laboratory use
• ISO 6353-1 / ISO 6353-2 / ISO 6353-3 - Reagents for chemical analysis
• ISO 760 - Additional details on Karl Fischer titration techniques

Keywords: ISO 14897:2023, polyols, water content, Karl Fischer, coulometric titration, amperometric titration, automated titration, polyurethanes, quality control, laboratory method.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 14897
Third edition
2023-06
Plastics — Polyols for use in the
production of polyurethanes —
Determination of water content
Plastiques — Polyols destinés à la production de polyuréthanes —
Dosage de l'eau
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: [phone]
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Application .2
6 Interferences . 2
7 Reagents . 3
7.1 Purity of reagents . 3
7.2 Purity of water . 3
7.3 Reagents for Method A (manual titration) . 3
7.4 Reagent for Method B . 3
8 Apparatus . 3
8.1 Apparatus for Method A (manual titration) . 3
8.2 Apparatus for Method B (automated titration) . 4
9 Sampling . 4
10 Standardization of reagent . 5
10.1 Standardization of reagent for Method A (manual titration) . 5
10.2 Standardization of reagent for Method B (automatic amperometric or coulometric
titration) . 5
10.3 Calculation . 6
11 Procedure . 6
11.1 Procedure for Method A (manual titration) . 6
11.2 Procedure for Method B (amperometric or coulometric titration) . 6
12 Expression of results .6
13 Precision and bias .7
13.1 General . 7
13.2 Precision and bias for Method B . 7
13.2.1 Precision . 7
13.2.2 Bias . 8
14 Test report . 8
Annex A (informative) Interlaboratory precision studies . 9
Bibliography .10
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC61, Plastics, Subcommittee SC12,
Thermosetting materials.
This third edition cancels and replaces the second edition (ISO 14897:2002), of which it constitutes a
minor revision.
The changes are as follows:
— the title has been changed to plural form to read: "Plastics — Polyols for use in the production of
polyurethanes — Determination of water content".
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
This method is for the determination of water content in polyether polyols, which are used in the
preparation of polyurethane prepolymers and polyurethane products. Knowledge of this value is
important to polyurethane production.
The document is based on ASTM D 4672.
v
INTERNATIONAL STANDARD ISO 14897:2023(E)
Plastics — Polyols for use in the production of
polyurethanes — Determination of water content
WARNING — Persons using this document should be familiar with normal laboratory practice.
This document does not purport to address all of the safety problems, if any, associated with
its use. It is the responsibility of the user of this document to establish appropriate safety and
health practices and to determine applicable national regulatory conditions prior to use.
1 Scope
This document specifies methods used to measure the water content of polyols employed as
polyurethane raw materials.
Method A is a manual amperometric method which has been included to better define the principles
of the Karl Fischer measurement. Amperometric methods are applicable to a wide range of polyols,
including those which have enough colour to obscure a visual end-point. Method B includes an
automated amperometric procedure and an automated coulometric procedure.
The coulometric procedure is an absolute method that does not require calibration and gives improved
sensitivity compared with amperometric methods.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 6353-1, Reagents for chemical analysis — Part 1: General test methods
ISO 6353-2, Reagents for chemical analysis — Part 2: Specifications — First series
ISO 6353-3, Reagents for chemical analysis — Part 3: Specifications — Second series
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
polyol
organic compound containing two or more hydroxyl groups suitable for reaction with isocyanates
3.2
polyurethane
polymer prepared by the reaction of an organic di- or polyisocyanate with compounds containing two
or more hydroxyl groups
Note 1 to entry: Polyurethanes may be thermosetting, thermoplastic, rigid or soft and flexible, cellular or non-
cellular.
4 Principle
4.1 Methods A and B are based on amperometric or coulometric titrations with Karl Fischer reagent.
The sulfur dioxide in the reagent first reacts with the alcohol to form an ester which is neutralized by
the base present in the reagent. The anion of the alkyl sulfurous acid is the reactive component. The
titration of water present constitutes the oxidation of the alkyl sulfite to alkyl sulfate by the iodine,
[4]
which consumes the water. The reaction can be formulated as follows :
ROH + SO + R’N → (R’NH)SO R
2 3
H O + I + (R’NH)SO R + 2R’N → (R’NH)SO R + 2(R’NH)I
2 2 3 4
4.2 To determine water, Karl Fischer reagent [a solution of iodine, sulfur dioxide, ethylene glycol
monomethyl ether (HOCH CH OCH ) and pyridine or a pyridine substitute] is added to a solution
2 2 3
of the test portion in methanol or another alcohol until all of the water present has been consumed.
In an amperometric titration, this is evidenced by a current-measuring device that indicates the
depolarization of a pair of platinum electrodes. In coulometric titrations, the iodine reagent is generated
electrically, thus eliminating the need for standardization of the reagent.
5 Application
These test methods are suitable for quality control, as a specification test for products, and for research.
The water content of a polyol is important because water reacts with isocyanates to form carbon
dioxide and an amine which consumes additional isocyanate.
NOTE The description of the manual system presented below is principally for reference purposes and has
been included in order to better define the principles of the Karl Fischer measurement. Commercially available
automated Karl Fischer titrators of the type described in Method B are used extensively. Additional details and
diagrams are available in ISO 760.
6 Interferences
6.1 Oxides, hydroxides and strongly basic compounds react with Karl Fischer reagent, producing an
equivalent amount of water, thus giving falsely high results. Therefore, this method shall not be used
for crude polyols containing KOH or other highly basic products unless corrections are made for the
excess water produced.
6.2 Amine-based polyols can shift the pH of the Karl Fischer syste
...