ISO/PRF 23157

Determination of the silanol group content on the surface of fumed silica -- Reaction gas chromatographic method

Titre manque

General Information

• Status: Published
• ICS: 87.060.10 - Pigments and extenders
• Technical Committee: ISO/TC 256 - Pigments, dyestuffs and extenders
• Drafting Committee: ISO/TC 256/WG 2 - Nanotechnological properties of pigments and extenders

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 2021

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Published in Switzerland
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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

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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

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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 definitions

For 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
...