ISO 4764:2024

Plastics - Polyols for use in the production of polyurethanes - Determination of degree of unsaturation by using iodine method

This document specifies a method for quantifying the total unsaturation using an addition reaction of the interhalogen compound iodine monochloride (ICl), using glacial acetic acid as a solvent as a method for measuring the total unsaturation of a polyether polyol for polyurethanes. It is not applicable to unsaturated compounds that are conjugated with a carbonyl group, a carboxyl group, or a nitrile group.

Plastiques — Polyols pour la production des polyuréthanes — Détermination du degré de non-saturation par la méthode à l'iode

General Information

• Status: Published
• Publication Date: 15-Sep-2024
• ICS: 83.080.10 - Thermosetting materials
• Technical Committee: ISO/TC 61/SC 12 - Thermosetting materials
• Drafting Committee: ISO/TC 61/SC 12/WG 6 - Polyurethane raw materials
• Current Stage: 6060 - International Standard published
• Start Date: 16-Sep-2024
• Due Date: 14-May-2025
• Completion Date: 16-Sep-2024

Overview

ISO 4764:2024 - Plastics - Polyols for use in the production of polyurethanes - Determination of degree of unsaturation by using iodine method specifies a laboratory titration method to quantify the degree of unsaturation in polyether polyols used for polyurethanes. The method uses the Wijs reagent (iodine monochloride, ICl) in glacial acetic acid as the addition reagent, followed by liberation of iodine with KI and titration with sodium thiosulfate. It is not applicable to unsaturations conjugated with carbonyl, carboxyl or nitrile groups.

Key topics and requirements

• Principle: Addition of ICl (Wijs reagent) to carbon–carbon double bonds; liberated iodine is titrated with standardized 0.1 N sodium thiosulfate using starch as an indicator. The degree of unsaturation is calculated from blank-corrected titration volumes.
• Reagents and solvents: Preparation and storage of Wijs reagent; examples of analytical solvents (methanol, ethanol, propanols, cyclohexane, chloroform). Use of KI solution and starch indicator is required.
• Apparatus: Standard laboratory glassware and volumetric/gravimetric equipment per referenced ISO laboratory glassware standards.
• Procedure: Dissolve sample in solvent, add Wijs reagent, incubate in the dark (1 h), add KI, then titrate liberated iodine with sodium thiosulfate. Use blank titration and apply calculation U = (B − V) × F / (2 S) to express unsaturation in meq/g (as given in the standard).
• Correction for additives: If antioxidants or other additives with unsaturated bonds are present (e.g., BHT), measure the additive separately and apply the correction formulas provided.
• Limitations: Not suitable for conjugated unsaturated systems; precision and bias data were not available at publication.

Applications and who uses it

• Quality control and incoming inspection for polyurethane polyols manufacturers and converters.
• R&D and polymer chemistry laboratories monitoring unsaturation levels that affect curing, crosslinking and final polymer properties.
• Contract testing and certification labs performing comparative analysis or replacing mercury-based methods.
• Environmental and safety-conscious labs transitioning from mercuric acetate titration (ISO 17710) to a non-mercury alternative.

Related standards

• ISO 17710 (mercuric acetate method - historical comparator)
• ISO laboratory glassware and reagent standards cited in the document: ISO 385, ISO 472, ISO 648, ISO 1042, ISO 4797, ISO 6353 series, ISO 8655 parts.

Keywords: ISO 4764:2024, degree of unsaturation, polyols, polyurethanes, iodine method, Wijs reagent, iodine monochloride, ICl, titration, sodium thiosulfate, additive correction.

Standards Content (Sample)

International
Standard
ISO 4764
First edition
Plastics — Polyols for use in the
2024-09
production of polyurethanes
— Determination of degree of
unsaturation by using iodine method
Plastiques — Polyols pour la production des polyuréthanes —
Détermination du degré de non-saturation par la méthode à l'iode
Reference number
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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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 . 1
5 Solvents and reagents . . 2
5.1 Solvents .2
5.2 Reagents .2
5.2.1 Wijs reagent .2
5.2.2 0,1 N sodium thiosulfate solution .2
5.2.3 KI solution .3
5.2.4 Starch indicator .3
6 Apparatus . 3
7 Procedure . 3
8 Correction . 4
9 Degree of unsaturation after correction. 4
10 Precision and bias . 5
11 Test report . 5
Annex A (informative) Correction of effect by additives . 6
Annex B (informative) Experimental results using conventional polyols . 7
Annex C (informative) Effect of differences of solvent . 8
Bibliography . 9

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12, Thermosetting
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iv
Introduction
Conventionally, a titration method using mercuric acetate (see ISO 17710) has been used as a method for
measuring a polyether polyol for polyurethanes. However, in recent years, the treatment of mercury waste
liquid associated with analysis has become a global problem.
This document formulates a measurement method to replace the mercuric acetate method.

v
International Standard ISO 4764:2024(en)
Plastics — Polyols for use in the production of
polyurethanes — Determination of degree of unsaturation
by using iodine method
1 Scope
This document specifies a method for quantifying the total unsaturation using an addition reaction of the
interhalogen compound iodine monochloride (ICl), using glacial acetic acid as a solvent as a method for
measuring the total unsaturation of a polyether polyol for polyurethanes. It is not applicable to unsaturated
compounds that are conjugated with a carbonyl group, a carboxyl group, or a nitrile group.
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 385, Laboratory glassware — Burettes
ISO 472, Plastics — Vocabulary
ISO 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 4797, Laboratory glassware — Boiling flasks with conical ground joints
ISO 6353-2, Reagents for chemical analysis — Part 2: Specifications — First series
ISO 6353-3, Reagents for chemical analysis — Part 3: Specifications — Second series
ISO 8655-2, Piston-operated volumetric apparatus — Part 2: Pipettes
ISO 8655-3, Piston-operated volumetric apparatus — Part 3: Burettes
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 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/
4 Principle
After dissolving the sample in a solvent, the carbon-carbon unsaturated compound in the sample is added
with glacial acetic acid solution of iodine monochloride (Wijs reagent) and left in a dark place to add iodine.
After completion of the addition reaction, add aqueous solution of potassium iodide, liberate iodine and
titrate with a sodium thiosulfate solution. When the colour of the solution turns pale yellow, add a starch
solution and titrate until the blue disappears. The degree of unsaturation is calculated from the difference
from the blank measured at the same time.

5 Solvents and reagents
5.1 Solvents
Use analytical-grade solvents, such as
5.1.1 methanol, as specified in ISO
...