ISO 21257:2018

INTERNATIONAL ISO
STANDARD 21257
First edition
2018-10
Plastics — Polymer polyols for use
in the production of polyurethane
— Determination of the residual
acrylonitrile and styrene monomer
content by gas chromatography
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

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 . 2
6 Apparatus . 2
7 Preparation of calibration solution and sample solution . 3
7.1 General . 3
7.2 Method A for using OT column . 3
7.2.1 Preparation of internal standard solution . 3
7.2.2 Preparation of calibration solutions . 3
7.2.3 Preparation of sample solution . 4
7.3 Method B for using packed column . 4
7.3.1 Preparation of internal standard solution . 4
7.3.2 Preparation of calibration solutions . 4
7.3.3 Preparation of sample solution . 4
8 Procedure. 5
8.1 Gas chromatographic procedure . 5
8.2 Measurement of sample solutions and calibration solutions . 5
8.3 Evaluation of gas chromatographic peak . 6
9 Expression of the results . 6
9.1 Preparation of the calibration curve . 6
9.2 Calculation of results from a calibration graph . 7
9.3 Calculation of results from a single-point calibration . 8
9.4 Acceptability of results and measurement sensitivity . 9
10 Precision . 9
11 Test report . 9
Annex A (informative) Typical analytical conditions .10
Annex B (informative) Typical examples of GC chromatogram .12
Annex C (informative) Precision .14
Bibliography .15
Foreword
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12,
Thermosetting materials.
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complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2018 – All rights reserved

Introduction
Polymer polyols are defined as very fine and stable dispersions of solid, vinylic polymers (for example,
acrylonitrile/styrene copolymers are typical) in liquid polyether polyols.
Polymer polyol is used to improve the physical properties of seat cushions, especially hardness. Because
the toxicity of acrylonitrile and styrene is high, it is important to establish an analytical method to
determine residual amounts of these reactants.
The importance of residual toxicity has increased with the use of polyurethane foam, etc. which comes
in contact with food and skin. This document is intended to help manufacturers evaluate the safety of
their products.
Annexes A, B and C complement the main body of this document and not meant to be a normative part
of this document.
INTERNATIONAL STANDARD ISO 21257:2018(E)
Plastics — Polymer polyols for use in the production
of polyurethane — Determination of the residual
acrylonitrile and styrene monomer content by gas
chromatography
1 Scope
This document specifies a method for the determination of the residual acrylonitrile monomer and
styrene monomer in polymer polyols by gas chromatography.
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
ISO 648, Laboratory glassware — Single-volume pipettes
ISO 1042, Laboratory glassware — One-mark volumetric flasks
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle
The polymer polyol sample is dissolved in a suitable solvent. This sample solution is then analysed using
gas chromatography with internal standardization. The amounts of residual acrylonitrile monomer and
styrene monomer are determined from peak areas using a previously established calibration curve.
NOTE Because of the high molecular weight of substances which are part of the polymer polyol, and because
these are injected directly into the chromatograph, injector contamination can occur which will lead to erroneous
results.
Monitor the condition of the chromatographic parts and clean or replace as necessary.
An injector liner packed with glass wool has been used to improve vaporization and ease of cleaning.
5 Reagents and materials
5.1 Solvent, use analytical-grade methanol, N, N-dimethylformamide, tetrahydrofuran, dipropylene
glycol monomethyl ether or toluene.
Other solvents can also be used if suitable results are obtained for the retention time, thermal stability
and separation performance.
5.2 Internal standard, shall be selected based on the retention times of the volatile materials
contained in the polymer polyol sample and the solvent.
Recommended combinations of solvent from 5.1 and internal standard are methanol and 2-methyl-
1-propanol, N, N-dimethylformamide and ethylbenzene, dipropylene glycol monomethyl ether and
bromobenzene.
Other combinations are also possible if the retention times, thermal stability and separation
performance are suitable.
5.3 Carrier gases and fuel gases for gas chromatograph.
Use helium or nitrogen as carrier gas, hydrogen as fuel gas, dry air as supporting fuel gas.
6 Apparatus
Normal laboratory equipment and the following apparatus are required.
6.1 Gas chromatograph, with flame ionization detector and capable of employing packed or open
tubular columns with either split or splitless injector. Typical operating conditions are described in
Annex A.
6.1.1 Injection port, for liquid samples.
When using open tubular column (hereafter called an OT column), an injection port with splitter may
be applicable.
6.1.2 Column and packing material.
The column diameter and length, as well as the packing material and liquid phase, are to be selected
based on consideration of column resolution (Re) and calibration curve linearity. Both packed columns
and OT (capillary) columns (hereafter referred to as OT columns) are acceptable.
Typical columns are described in Annex A.
— OT columns: The OT column are to be selected from suitable manufacturer(s), and then shall be
conditioned sufficiently.
— Packed columns: The packed column should be packed with the liquid phase and support particles
from suitable manufacturer(s), and then conditioned sufficiently.
6.1.3 Detector, hydrogen flame ionization detector (hereafter referred to as FID).
6.2 Data processor, selected based on suitability for recording the signals from the detector and
processing the chromatograms.
6.3 Sample injection syringe, micro-syringe with a volume range 1 μL to 50 μL. Manual and
autoinjector syringes are suitable.
2 © ISO 2018 – All rights reserved

6.4 Analytical balance, capable of measuring to 0,1 mg, is required.
6.5 One-mark volumetric flasks (hereafter volumetric flasks), as specified in ISO 1042.
Needed volumes are 50 mL and 500 mL.
6.6 Single-volume pipettes (hereafter volumetric pipettes), as specified in ISO 648.
Needed volumes are 0,5 mL, 1,0 mL, 2,0 mL 5,0 mL and 10,0 mL.
NOTE Graduated pipettes (ISO 835) and piston pipettes (ISO 8655) are also suitable.
7 Preparation of calibration solution and sample solution
7.1 General
Two sample preparation methods are described in 7.2 and 7.3. Method A is to be used for an OT-column
chromatograph and Method B is used for a packed-column chromatograph. The range of calibration
concentrations should be selected based on expected levels of acrylonitrile and styrene monomers.
Calibrations with 4 levels of each monomer are to be used.
7.2 Method A for using OT column
7.2.1 Preparation of internal standard solution
Into a 500 mL volumetric flask, weigh to the nearest 1 mg, the amount of internal standard specified in
Table 1. Add solvent to make 500 mL, stopper tightly and mix well. This solution is hereafter called the
internal standard solution.
7.2.2 Preparation of calibration solutions
Weigh the amounts of acrylonitrile and/or of styrene specified in Table 1, to the nearest 1 mg, into a
500 mL volumetric flask. Add solvent to make 500 mL, stopper tightly and mix well. This solution is
hereafter called the acrylonitrile/styrene solution.
Into a 50 mL volumetric flask, pipet 0,5 mL of the acrylonitrile/styrene solution and 5,0 mL of the
internal standard solution. Add solvent to make 50 mL, stopper tightly and mix well. Prepare three
additional solutions by pipetting
...