ISO 24698-1:2018

INTERNATIONAL ISO
STANDARD 24698-1
Second edition
2018-09
Rubber, raw — Determination of bound
acrylonitrile content in acrylonitrile-
butadiene rubber (NBR) —
Part 1:
Combustion (Dumas) method
Caoutchouc brut — Détermination du contenu en acrylonitrile lié
dans le caoutchouc acrylonitrile-butadiène (NBR) —
Partie 1: Méthode par combustion (Dumas)
Reference number
ISO 24698-1:2018(E)
©
ISO 2018

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ISO 24698-1:2018(E)

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ii © ISO 2018 – All rights reserved

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ISO 24698-1:2018(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents and materials . 2
6 Apparatus . 2
7 Sampling and preparation of the sample for the determination . 3
7.1 Raw NBR, XNBR or NBIR rubber . 3
7.2 NBR latex . 3
8 Procedure. 4
9 Calculation of bound acrylonitrile content . 4
10 Precision . 5
11 Test report . 5
Annex A (informative) Examples of automatic analysers based on the Dumas combustion
method . 6
Annex B (informative) Precision . 7
Bibliography . 9
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ISO 24698-1:2018(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
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URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 45, Rubber and rubber products,
Subcommittee SC 3, Raw materials (including latex) for use in the rubber industry.
This second edition cancels and replaces the first edition (ISO 24698-1:2008), which has been
technically revised.
The main changes compared to the previous edition are as follows:
— addition in the scope of two types of raw rubbers, XNBR and NBIR, that contain acrylonitrile;
— addition of specified argon gas as carrier gas in 5.3;
— amendment of finishing condition of sample weight in 7.1 and 7.2.
A list of all the parts in the ISO 24698 series can be found on the ISO website.
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.
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INTERNATIONAL STANDARD ISO 24698-1:2018(E)
Rubber, raw — Determination of bound acrylonitrile
content in acrylonitrile-butadiene rubber (NBR) —
Part 1:
Combustion (Dumas) method
WARNING — Persons using this document should be familiar with normal 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.
CAUTION — Certain procedures specified in this document might involve the use or generation
of substances, or the generation of waste, that could constitute a local environmental hazard.
Reference should be made to appropriate documentation on safe handling and disposal after use.
1 Scope
This document specifies a method for the determination of the bound acrylonitrile content in NBR
by an automatic analyser which uses a combustion process. The method is also applicable to XNBR
(carboxylic acrylonitrile-butadiene rubber) and NBIR (acrylonitrile- butadiene-isoprene rubber) as
well as NBR latex.
NOTE This document and ISO 24698-2 can give different results on the same rubber sample.
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 123, Rubber latex — Sampling
ISO 1407:2011, Rubber — Determination of solvent extract
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at http: //www .iso .org/obp
— IEC Electropedia: available at https: //www .electropedia .org/
4 Principle
The nitrogen in a sample of raw rubber is converted into oxides of nitrogen in an atmosphere of high-
purity oxygen in the combustion unit of the analyser. The oxides of nitrogen are then converted into
elemental nitrogen by a catalyst in the reduction unit. The carbon dioxide and water vapour produced
are removed by absorption or another means of separation. Finally, the resultant gas is passed, with a
carrier gas, into a thermal conductivity detector (TCD) to determine the nitrogen content.
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ISO 24698-1:2018(E)

5 Reagents and materials
5.1 Reference materials:
— L-aspartic acid, purity ≥99 %;
— L-glutamic acid, purity ≥99 %;
— EDTA, purity ≥99 %.
5.2 Oxygen gas, purity ≥99,99 % or in accordance with the analyser manufacturer's instructions.
5.3 Carrier gases:
— helium gas, purity ≥99,995 % or in accordance with the analyser manufacturer's instructions;
— carbon dioxide gas, purity ≥99,995 % or in accordance with the analyser manufacturer's
instructions;
— argon gas, purity ≥99,995 % or in accordance with the analyser manufacturer's instructions.
5.4 Ethanol, purity ≥95 % by volume.
5.5 Methanol, purity ≥99,8 % by volume.
6 Apparatus
6.1 Automatic analyser.
6.1.1 General
The automatic analyser consists of the following components:
a) a combustion unit, capable of maintaining a minimum operating temperature in accorda
...