ISO/PRF 23157
(Main)Determination of the silanol group content on the surface of fumed silica -- Reaction gas chromatographic method
Determination of the silanol group content on the surface of fumed silica -- Reaction gas chromatographic method
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General Information
Standards Content (sample)
INTERNATIONAL ISO
STANDARD 23157
First edition
Determination of the silanol group
content on the surface of fumed
silica — Reaction gas chromatographic
method
PROOF/ÉPREUVE
Reference number
ISO 23157:2021(E)
ISO 2021
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ISO 23157:2021(E)
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ISO 23157:2021(E)
Contents Page
Foreword ..........................................................................................................................................................................................................................................v
Introduction ................................................................................................................................................................................................................................vi
1 Scope ................................................................................................................................................................................................................................. 1
2 Normative references ...................................................................................................................................................................................... 1
3 Terms and definitions ..................................................................................................................................................................................... 1
4 Principle ........................................................................................................................................................................................................................ 1
5 Reagents ........................................................................................................................................................................................................................ 2
5.1 General ........................................................................................................................................................................................................... 2
5.2 Toluene .......................................................................................................................................................................................................... 2
5.3 Grignard reagent ................................................................................................................................................................................... 2
5.4 Reaction solution .................................................................................................................................................................................. 2
5.5 Carrier gas and diluent gas ........................................................................................................................................................... 2
5.6 Auxiliary gases ........................................................................................................................................................................................ 2
5.7 Calibration substance ........................................................................................................................................................................ 2
6 Apparatus ..................................................................................................................................................................................................................... 3
6.1 Gas chromatograph ............................................................................................................................................................................. 3
6.2 Headspace system ................................................................................................................................................................................ 3
6.3 Oven .................................................................................................................................................................................................................. 3
6.4 Capillary column.................................................................................................................................................................................... 3
6.5 Sample vials ............................................................................................................................................................................................... 4
6.6 Analytical balance................................................................................................................................................................................. 4
6.7 Gas collecting bag ................................................................................................................................................................................. 4
6.8 Syringe............................................................................................................................................................................................................ 4
7 Sample pre-treatment and reaction ................................................................................................................................................. 4
7.1 Sample pre-treatment ....................................................................................................................................................................... 4
7.1.1 Determination of matter volatile at 105 °C in fumed silica......................................................... 4
7.1.2 Preparation of the test sample ............................................................................................................................. 4
7.2 Blank test ..................................................................................................................................................................................................... 4
7.3 Reaction ........................................................................................................................................................................................................ 5
7.4 Analysis.......................................................................................................................................................................................................... 5
7.4.1 Headspace system conditions .............................................................................................................................. 5
7.4.2 Gas chromatographic conditions ....................................................................................................................... 5
7.4.3 Identification ....................................................................................................................................................................... 5
7.4.4 Calibration ............................................................................................................................................................................. 5
7.4.5 Measurement ...................................................................................................................................................................... 6
8 Calculation .................................................................................................................................................................................................................. 6
8.1 Calculation of the methane quantity produced in the vials ............................................................................. 6
8.2 Calculation of the silanol group content ........................................................................................................................... 7
8.2.1 Calculation of fumed silica volatile at 105 °C .......................................................................................... 7
8.2.2 Calculation of the silanol group content on the surface of fumed silica .......................... 7
9 Expression of results ........................................................................................................................................................................................ 7
10 Precision ....................................................................................................................................................................................................................... 7
10.1 General ........................................................................................................................................................................................................... 7
10.2 Repeatability limit, r ............................................................................................................................................................................7
10.3 Reproducibility limit, R .....................................................................................................................................................................8
11 Test report ................................................................................................................................................................................................................... 8
Annex A (informative) Representative chromatogram of methane ..................................................................................... 9
Annex B (informative) Information about precision ........................................................................................................................10
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ISO 23157:2021(E)
Bibliography .............................................................................................................................................................................................................................11
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ISO 23157:2021(E)
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
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.This document was prepared by Technical Committee ISO/TC 256, Pigments, dyestuffs and extenders.
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.© ISO 2021 – All rights reserved PROOF/ÉPREUVE v
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ISO 23157:2021(E)
Introduction
Fumed silica (pyrogenic silicon dioxide) has a relatively high concentration of silanol groups formed
during high-temperature flame hydrolysis and the following cooling process. This specified property
enables fumed silica to be widely used as a reinforcing filler, thickener, thixotropy-increasing and anti-
sagging additive in numerous industries, for example silicone rubber, coating materials, adhesives and
sealants.The determination of the silanol group content on the surface of fumed silica is essential for both
manufacturers and users to develop a high-performance, surface modified fumed silica and improve
existing products. Further, it also facilitates the communication among interested parties.
In practice, methods of titration, thermogravimetry (TG), infrared spectroscopy (IR) and reaction gas
chromatography can be a choice for the determination of the silanol group content on the surface of
fumed silica. Among these methods, the method of reaction gas chromatography is preferred by users
due to the advantage of higher sensitivity and better reproducibility.This document provides a detailed procedure for how to conduct the testing of the silanol group content
on the surface of fumed silica by means of the reaction gas chromatographic method.
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INTERNATIONAL STANDARD ISO 23157:2021(E)
Determination of the silanol group content on the surface
of fumed silica — Reaction gas chromatographic method
SAFETY STATEMENT — Persons using this document should be familiar with usual 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 to establish appropriate safety and health
practices and to determine applicability of any national regulatory conditions.IMPORTANT — It is absolutely essential that tests conducted in accordance to this document be
carried out by suitably qualified staff.1 Scope
This document specifies a method for the determination of the silanol group content on the surface of
fumed silica by reaction gas chromatographic method.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 18451-1, Pigments, dyestuffs and extenders — Terminology — Part 1: General terms
3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 18451-1 and the following
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 https:// www .electropedia .org/
3.1
fumed silica
amorphous silica produced from silicon halides by high-temperature flame hydrolysis
[SOURCE: ISO 18473-3:2018, 3.1]3.2
silanol group
hydroxyl group on the surface of fumed silica
4 Principle
A suitable amount of the dried fumed silica sample reacts with the Grignard reagent dispersed in
toluene in an airtight reaction bottle to produce methane, which is injected into a gas chromatograph for
separation, and further detected by a flame ionization detector (FID). The...
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