ISO 24862:2026

• Abstract:

  This document specifies a method to measure the total unsaturation of polyether polyols used in the production of polyurethanes by a Raman spectrometric method. It is not applicable to unsaturated compounds that are conjugated with a carbonyl group, a carboxyl group, or a nitrile group.

• Status: Published
• Publication Date: 13-Oct-2026
• ICS: 83.100 - Cellular 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: 14-Oct-2026
• Completion Date: 14-Oct-2026

ISO 24862:2026 is an ISO standard for measuring the total unsaturation of polyether polyols used in polyurethane production. It specifies a Raman spectrometric method for identifying and quantifying allyl and cis-propenyl unsaturation in polyols, and it gives a practical alternative to the mercuric acetate titration approach used in ISO 17710.

What does ISO 24862:2026 specify?

ISO 24862:2026 specifies a test method for the total unsaturation of polyether polyols by Raman spectrometry. The scope is narrow on purpose: it is aimed at polyols used to make polyurethanes, and it excludes unsaturated compounds that are conjugated with a carbonyl group, a carboxyl group, or a nitrile group.

The document is organized as a full test method. After the scope, it gives normative references, terms and definitions, the measurement principle, reagents and materials, apparatus, procedure, calculation of degree of unsaturation, and the test report. Three informative annexes provide worked examples, measurement setups, and example Raman spectra.

Annex	What it covers
Annex A	Example of relative scattering intensity measurement
Annex B	Example of unsaturation measurement
Annex C	Example of Raman spectrums

What are the key requirements of ISO 24862:2026?

ISO 24862:2026 sets out a Raman-based workflow: prepare the polyol with an internal standard, measure the relevant Raman peaks, determine relative scattering intensities from model compounds, and then calculate the allyl, cis-propenyl, and total degree of unsaturation. In practice, that means the laboratory has to control sample preparation, instrument settings, and peak evaluation closely enough that the result can be compared across runs.

Applicability and sample approach

Clause 1 limits the method to polyether polyols used in polyurethane production, and Clause 4 makes clear that the result is the total unsaturation made up of allyl and cis-propenyl contributions. The introduction also explains the practical reason for the method: it is meant to replace the older mercury-based titration approach with a Raman method that is easier to handle from a waste-management point of view.

Principle of the measurement

Clause 4 states that the Raman shifts of the C=C stretching bands for allyl and cis-propenyl groups are measured against an internal standard. The document uses the 1 649 cm^-1 band for allyl groups and the 1 670 cm^-1 band for cis-propenyl groups, with an internal-standard band around 1 580 cm^-1. In practice, the user compares peak heights rather than trying to read absolute signal intensity from the instrument.

Reagents and reference materials

Clause 5 names m-dichlorobenzene as the internal standard and uses allyl alcohol base ethers and cis-propenyl alcohol base ethers as model compounds. That matters because the method depends on measured relative scattering intensity values from these reference materials before the sample result can be calculated.

Apparatus and measurement conditions

Clause 6 recommends normal laboratory equipment plus three specific items: a Raman spectrometer, a measuring cell, and an analytical balance. The spectrometer should use a 532 nm laser, and for quantitative work the detector’s relative intensity should be calibrated across the measurement range. If that calibration is not feasible, the document recommends a CCD or CMOS detector with a 532 nm laser to support consistency and comparability.

The spectrometer should cover at least 1 500 cm^-1 to 1 750 cm^-1, with a wider range of 100 cm^-1 to 3 500 cm^-1 recommended, and a spectral resolution of at least 6 cm^-1. The measuring cell is a capillary with at least a 1 mm inner diameter, and Clause 6 allows equivalent cells if they can be shown to give the same results. For the balance, the document calls for 0,000 1 g readability and 0,001 g weighing accuracy.

Procedure and peak handling

Clause 7 describes adding the internal standard to the sample, mixing thoroughly, and measuring the spectrum over 1 500 cm^-1 to 1 750 cm^-1. The annexes show practical setups using either vials or capillaries, which helps the reader match the method to the available instrument.

Annex A and Annex B also show how to separate the relevant Raman bands from nearby signals and how to set a baseline before reading peak height. In practice, that means the analyst must choose a repeatable way to define peak intensity, because the final unsaturation value depends on those peak-height measurements.

Calculation and reporting

Clause 8 gives the calculation steps. First, the relative scattering intensity for allyl and cis-propenyl model compounds is determined. Then the sample’s allyl unsaturation and cis-propenyl unsaturation are calculated separately, and the total degree of unsaturation is the sum of the two values.

Clause 9 defines what has to appear in the test report. The report needs the standard reference, sample identification, internal standard and model-compound details, test conditions, sample and reference masses, the calculated factors and unsaturation values, the date of analysis, and the name of the measurer. That gives traceability for quality control, supplier checks, and disputes about results.

What terms does ISO 24862:2026 define?

ISO 24862:2026 uses the terms and definitions from ISO 472, so the vocabulary follows the plastics terminology already established for the field.

• Polyether polyol - the polyol type covered by the method, used in polyurethane production.
• Internal standard - the reference material added to the sample so Raman peak intensity can be compared on a relative basis.
• Model compound - a reference compound used to determine the relative scattering intensity for a known unsaturation type.
• Allyl group - one of the unsaturated terminal groups measured by the method.
• cis-propenyl group - the other unsaturated terminal group measured by the method.
• Degree of unsaturation - the amount of unsaturation reported in meq/g for the allyl, cis-propenyl, and total sample values.
• Raman spectrometer - the instrument used to record Raman scattering peaks for the measurement.

Who uses ISO 24862:2026?

ISO 24862:2026 is used by laboratories that test polyols for polyurethane production, by manufacturers that need incoming or in-process control, and by quality teams that have to compare batches against a specification. It is also relevant to buyers and suppliers who need a repeatable way to check unsaturation in polyether polyols without using the older mercury-based titration approach.

The informative annexes make the standard especially useful for analysts who need a practical starting point for instrument setup, peak separation, and result calculation.

Which standards are used with ISO 24862:2026?

ISO 24862:2026 cites ISO 472 in Clause 2, and ISO 472 supplies the plastics vocabulary used in Clause 3. That keeps the terminology aligned with the broader ISO plastics framework.

ISO 17710 is named in the introduction and in the bibliography as the microtitration method that this document is intended to replace and compare against. ISO 6775 is also listed in the bibliography as a related Raman spectrometric identification standard for plastics.

What does the ISO 24862:2026 document contain?

ISO 24862:2026 contains a full analytical method, not just a short requirement list. It gives the test principle, the required internal standard and model compounds, the instrument and cell recommendations, the measurement range, and the calculation formulas for relative scattering intensity and unsaturation.

The annexes add worked examples for relative scattering intensity measurement, worked examples for polyol unsaturation measurement, and example Raman spectra for the polyols and model compounds. Annex B also shows a comparison between the Raman method and ISO 17710 microtitration results, which helps users judge whether their own implementation is producing plausible values.

International
Standard
ISO 24862
First edition
Plastics — Polyols for use in the
2026-10
production of polyurethanes
— Determination of degree of
unsaturation for polyols by Raman
spectrometric method
Plastiques — Polyols destinés à la production de polyuréthanes
— Détermination du degré d'insaturation des polyols par
spectrométrie Raman
Reference number
© ISO 2026
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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 . 1
5 Reagents and materials . 1
5.1 Internal standard .1
5.2 Model compounds .2
6 Apparatus . 2
6.1 Raman spectrometer .2
6.2 Measuring cell .2
6.3 Analytical balance .2
7 Procedure . 2
8 Calculation of degree of unsaturation . 3
9 Test report . 4
Annex A (informative) Example of relative scattering intensity measurement . 6
Annex B (informative) Example of unsaturation measurement .11
Annex C (informative) Example of Raman spectrums .16
Bibliography . 19

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 degree of unsaturation of polyether polyols for polyurethanes. However, in recent years, the
treatment of mercury waste liquid associated with analysis has become a global problem.
This document is intended to replace the mercuric acetate titration method with a more facile and
environmentally friendly Raman spectrometric method.

v
International Standard ISO 24862:2026(en)
Plastics — Polyols for use in the production of polyurethanes
— Determination of degree of unsaturation for polyols by
Raman spectrometric method
1 Scope
This document specifies a method to measure the total unsaturation of polyether polyols used in the
production of polyurethanes by a Raman spectrometric method. 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 472, Plastics — Vocabulary
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
-1
The Raman shifts of the C=C bond stretching of allyl and cis-propenyl groups appear at 1 649 cm and
-1
1 670 cm , respectively.
The intensities of both peaks can be measured relative to the intensity of an internal standard peak.
-1
Compounds without peaks in the 1 600 to 1 700 cm region and with appropriate peaks in the immediate
vicinity can be used as an internal standard. Because m-dichlorobenzene has aromatic ring C=C peak
-1
appearing at 1 580 cm , it can be used as an internal standard.
The relative intensity of each unsaturated terminal group, allyl and cis-propenyl, are determined using
model compounds.
On the basis of the above relative intensities, degree of unsaturation of the allyl and the cis-propenyl groups
in polyether polyols are individually determined.
The total degree of unsaturation can be calculated by addition of both values.
5 Reagents and materials
5.1 Internal standard
m-Dichlorobenzene
5.2 Model compounds
Allyl alcohol base ethers
cis-Propenyl alcohol base ethers
6 Apparatus
Normal laboratory equipment and the following apparatus are recommended.
6.1 Raman spectrometer
A Raman spectrometer with a 532 nm laser excitation source should be used.
For quantitative analysis, calibration of the detector's relative intensity across the measurement range shall
be performed.
If such calibration is not feasible, the use of a CCD or CMOS detector in combination with a 532 nm laser
excitation source should be adopted to ensure consistency and comparability of results.
-1 -1
The Raman spectrometer should at least have a spectral range of 1 500 cm to 1 750 cm , however a wider
-1 -1 -1
spectral range of 100 cm to 3 500 cm is recommended. Spectral resolution of at least 6 cm is required.
6.2 Measuring cell
Capillary with at least a 1 mm inner diameter.
NOTE Equivalent measuring cells matching a particular Raman spectrometer can be used if they can be shown to
lead to the same results.
6.3 Analytical balance
Readability 0,000 1 g and weighing accuracy 0,001 g.
7 Procedure
The scattering intensity of the C=C stretch band of the allyl and cis-propenyl group are determined by
comparing the peak height with the internal reference band. The compounds without bands in the (1 600 to
-1
1 700) cm region and with appropriate bands in the immediate vicinity can be used as internal reference
-1
materials. Because m-dichlorobenzene (b.p. 173 °C) has aromatic ring C=C peak appearing at 1 580 cm , it
can be used as an internal standard. For example, in a sample with a total unsaturation of 0,05 meq/g, about
30 mg of m-dichlorobenzene is added to 0,5 g of sample, stirred thoroughly, and encapsulated in a capillary
with an inner diameter of 1 mm for measurement.
-1
The measurement area is (1 500 to 1 750) cm including the three C=C stretch bands described above.
An example of a measured chart is shown in Figure 1.
Measurement conditions and spectra for other measurement examples are shown in Annexes A, B and C.

Key
-1
X Raman shift, cm
Y intensity (arbitrary unit)
1 cis-propenyl
2 allyl
3 phenylene
[ ]
Figure 1 — Example of Raman spectrum of C = C stretching peaks 1
8 Calculation of degree of unsaturation
From the measurement data of the model compound, the relative scattering intensity f and f of per unit
a p
degree of unsaturation for the internal reference band of the allyl or cis-propenyl groups can be determined
according to the following definitions.
Calculate the relative scattering intensity of the allyl group of per unit degree of unsaturation f as shown in
a
Formula (1):
f =I /I (a) × w (a)/w × 1/x (1)
a a i i a a
where
f is the relative scattering intensity of the allyl group of per unit degree of unsaturation;
a
x is the unsaturated degree of the allyl group terminal model compound, in meq/g;
a
-1
I is the intensity of Raman scattering peak (1 649 cm ) of the allyl group terminal model
a
compound;
-1
I (a) is the intensity of Raman scattering peak (1 580 cm ) of the internal standard;
i
w is the mass of the allyl group terminal model compound, in g;
a
w (a) is the mass of the internal standard, in g.
i
However, it should be noted that f does not contain the molecular weight of m-Dichlorobenzene, so it is not a
a
scattering intensity ratio per functional group.

Similarly, calculate the relative scattering intensity of the cis-propenyl group of per unit degree of
unsaturation f as shown in Formula (2):
p
f =I /I (p) × w (p)/w × 1/x (2)
p p i i p p
where
f is the relative scattering intensity of the cis-propenyl group of per unit degree of unsaturation;
p
x is the unsaturated degree of the cis-propenyl group terminal model compound, in meq/g;
p
-1
I is the intensity of Raman scattering peak (1 670 cm ) of the cis-propenyl group terminal model
p
compound;
-1
I (p) is the intensity of Raman scattering peak (1 580 cm ) of the internal standard;
i
w is the mass of the cis-propenyl group terminal model compound, in g;
p
w (p) is the mass of the internal standard, in g.
i
Next, calculate the degree of unsaturation of the allyl group X ,the degree of unsaturation of the cis-propenyl
a
group X meq/g of the sample as shown in Formulae (3) and (4):
p
X = { I (s)/I (s)} × {w (s)/w } × 1/f (3)
a a i i s a
X = {I (s)/I (s)} × {w (s)/w } × 1/f (4)
p p i i s p
where
X is the degree of unsaturation of the allyl group in the sample, in meq/g;
a
X is the degree of unsaturation of the cis-propenyl group in the sample, in meq/g;
p
-1
I (s) is the intensity of Raman scattering peak (1 649 cm ) of the allyl group in the sample;
a
-1
I (s) is the intensity of Raman scattering peak (1 670 cm ) of the cis-propenyl group in the sample;
p
-1
I (s) is the intensity of Raman scattering peak (1 580 cm ) of the internal standard;
i
w is the mass of the sample, in g;
s
w (s) is the mass of the internal standard, in g.
i
f is the relative scattering intensity of the allyl group of per unit degree of unsaturation;
a
f is the relative scattering intensity of the cis-propenyl group of per unit degree of unsaturation.
p
Therefore, calculate the total degree of unsaturation of the sample as shown in Formula (5):
X = X + X (5)
a p
where X is the total degree of unsaturation of the sample, in meq/g.
9 Test report
Th
...