ISO 14897:2023

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
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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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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
...