ISO 24698-1:2008
(Main)Rubber, raw — Determination of bound acrylonitrile content in acrylonitrile-butadiene rubber (NBR) — Part 1: Combustion (Dumas) method
Rubber, raw — Determination of bound acrylonitrile content in acrylonitrile-butadiene rubber (NBR) — Part 1: Combustion (Dumas) method
ISO 24698-1:2008 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 NBR latex.
Caoutchouc brut — Détermination du contenu en acrylonitrile lié dans le caoutchouc acrylonitrile-butadiène (NBR) — Partie 1: Méthode par combustion (Dumas)
General Information
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 24698-1
First edition
2008-05-15
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 24698-1:2008(E)
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ISO 2008
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ISO 24698-1:2008(E)
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ISO 24698-1:2008(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Principle . 1
4 Reagents and materials . 2
5 Apparatus . 2
6 Sampling and preparation of the sample for the determination . 3
7 Procedure . 3
8 Calculation of bound acrylonitrile content . 4
9 Precision . 4
10 Test report . 4
Annex A (informative) Examples of automatic analysers based on the Dumas combustion method . 5
Annex B (informative) Precision . 6
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ISO 24698-1:2008(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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 24698-1 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee
SC 2, Testing and analysis.
ISO 24698 consists of the following parts, under the general title Rubber, raw — Determination of bound
acrylonitrile content in acrylonitrile-butadiene rubber (NBR):
— Part 1: Combustion (Dumas) method
— Part 2: Kjeldahl method
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INTERNATIONAL STANDARD ISO 24698-1:2008(E)
Rubber, raw — Determination of bound acrylonitrile content in
acrylonitrile-butadiene rubber (NBR) —
Part 1:
Combustion (Dumas) method
WARNING — Persons using this part of ISO 24698 should be familiar with normal laboratory practice.
This part of ISO 24698 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
ensure compliance with any national regulatory conditions.
CAUTION — Certain procedures specified in this part of ISO 24698 may 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.
1Scope
This part of ISO 24698 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 NBR latex.
NOTE Parts 1 and 2 of this International Standard may not necessarily give the same result for any given rubber sample.
2 Normative references
The following referenced documents are indispensable for the application 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 1407:1992, Rubber — Determination of solvent extract
ISO 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
3 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 24698-1:2008(E)
4 Reagents and materials
4.1 Reference materials:
— L-aspartic acid, purity � 99 %;
— L-glutamic acid, purity � 99 %;
— EDTA, purity � 99 %.
4.2 Oxygen gas, purity � 99,99 % or in accordance with the analyser manufacturer's instructions.
4.3 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.
4.4 Ethanol, purity � 95 % by volume.
4.5 Methanol, purity � 99,8 % by volume.
5 Apparatus
5.1 Automatic analyser.
5.1.1 General
The automatic analyser consists of the following components:
a) a combustion unit, capable of maintaining a minimum operating temperature in accordance with the
manufacturer's instructions for combustion of the sample in an atmosphere of high-purity oxygen;
b) a high-purity oxygen feeder, capable of feeding enough high-purity oxygen for complete combustion;
c) a reduction unit, capable of fully converting liberated nitrogenous compounds to nitrogen gas;
d) an absorber (or another type of separator) of by-products, capable of removing the water and carbon
dioxide formed;
e) a TCD, capable of detecting the nitrogen gas formed;
f) a microprocessor, capable of calibrating the apparatus with a standard reference material and of converting
the detector response into mass % of nitrogen in the sample.
5.1.2 Performance requirements
The accuracy of the system shall be demonstrated by performing ten successive determinations using a
reference material such as L-aspartic acid, L-glutamic acid or EDTA. The mean of the ten determinations with
the reference material shall be within ± 0,2 percentage points of the theoretical value. The relative standard
deviation shall be within 0,5 % by mass of nitrogen for the reference material.
s
NOTE Relative standard deviation (%) = × 100
w
N
where
s i
...
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