ISO 9924-2:2016

INTERNATIONAL ISO
STANDARD 9924-2
Second edition
2016-08-01
Rubber and rubber products —
Determination of the composition of
vulcanizates and uncured compounds
by thermogravimetry —
Part 2:
Acrylonitrile-butadiene and
halobutyl rubbers
Caoutchouc et produits à base de caoutchouc — Détermination
de la composition des vulcanisats et mélanges non vulcanisés par
thermogravimétrie —
Partie 2: Caoutchoucs acrylonitrile-butadiène et butyl halogéné
Reference number
ISO 9924-2:2016(E)
©
ISO 2016

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ISO 9924-2:2016(E)

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ISO 9924-2:2016(E)

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Principle . 2
4 Reagents . 2
5 Apparatus . 2
6 Thermogravimetric analyser checks . 3
7 Procedure. 4
8 Expression of results . 5
9 Precision . 9
10 Test report . 9
Annex A (informative) Precision .10
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ISO 9924-2:2016(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 on 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 the following URL: www.iso.org/iso/foreword.html.
The committee responsible for this document is ISO/TC 45, Rubber and rubber products, SC 2, Testing
and analysis.
This second edition cancels and replaces the first edition (ISO 9924-2:2000), of which it constitutes
a minor revision. It also incorporates the amendment ISO 9924-2:2000/Amd 1:2012. The following
changes have been made:
— precision clause moved to Annex A.
ISO 9924 consists of the following parts, under the general title Rubber and rubber products —
Determination of the composition of vulcanizates and uncured compounds by thermogravimetry:
— Part 1: Butadiene, ethylene-propylene copolymer and terpolymer, isobutene-isoprene, isoprene and
styrene-butadiene rubbers
— Part 2: Acrylonitrile-butadiene and halobutyl rubbers
— Part 3: Hydrocarbon rubbers, halogenated rubbers and polysiloxane rubbers after extraction
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INTERNATIONAL STANDARD ISO 9924-2:2016(E)
Rubber and rubber products — Determination of the
composition of vulcanizates and uncured compounds by
thermogravimetry —
Part 2:
Acrylonitrile-butadiene and halobutyl rubbers
WARNING — Persons using this part of ISO 9924 should be familiar with normal laboratory
practice. This part of ISO 9924 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.
1 Scope
1.1 This part of ISO 9924 specifies a thermogravimetric method for the determination of the total
organic content, carbon black content, carbonaceous residue and ash in vulcanizates and uncured
compounds containing polymers which form a carbonaceous residue on pyrolysis (see 1.2). The loss in
mass at around 300 °C is an approximate guide to the volatile-matter content of the compound.
1.2 The method is suitable for the analysis of rubber compounds and vulcanizates containing the
hydrocarbon polymers covered by ISO 9924-1 plus the following copolymers with polar groups which
form a carbonaceous residue on pyrolysis:
a) acrylonitrile-butadiene copolymers (NBRs);
b) carboxylated acrylonitrile-butadiene copolymers (XNBRs);
c) hydrogenated acrylonitrile-butadiene copolymers (HNBRs);
d) chlorinated isobutylene-isoprene copolymers (CIIRs);
e) brominated isobutylene-isoprene copolymers (BIIRs).
NOTE 1 The field of application of the method may be extended to include the analysis of compounds
containing rubbers different from those given in this subclause, provided that the applicability of the method is
tested beforehand using known compounds or vulcanizates having similar composition.
NOTE 2 The method is not suitable for compounds containing mineral fillers, such as carbonates or hydrated
aluminium oxides, which decompose in the temperature range from 25 °C to 800 °C, unless suitable corrections
based on prior knowledge of filler behaviour can be made.
NOTE 3 The method is not suitable for the determination of the total polymer content of compounds
containing non-rubber organic ingredients that cannot be completely removed by solvent extraction carried out
in accordance with ISO 1407.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 1407, Rubber — Determination of solvent extract
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ISO 9924-2:2016(E)

3 Principle
3.1 A weighed test portion is heated, following a pre-set programme, from 40 °C to 600 °C in a stream
of nitrogen until all the organic material is pyrolysed. If nitrile-butadiene copolymers are present, a small
amount of the polymer will be pyrolysed to form a carbonaceous residue that has to be determined in
order to obtain the correct total organic content.
3.2 For this purpose, the oven temperature is decreased to 400 °C in a stream of nitrogen and
maintained at 400 °C for 5 min. The gas stream is then changed from nitrogen to air or oxygen and the
oven temperature raised slowly to 800 °C. During this heating in an oxidizing atmosphere, two distinct
losses in mass occur due to combustion. The first is due to the combustion of the carbonaceous residue,
and the amount is determined and added to the previously determined loss in nitrogen at 600 °C to
obtain the correct value of the total organic content. The second is due to the normal combustion of the
carbon black.
NOTE The total rubber content is calculated by subtracting the value of the solvent extract, determined
in accordance with ISO 1407, from the total organic content, provided that all non-rubber ingredients can be
extracted.
3.3 The mass of the residue at 800 °C represents the ash.
4 Reagents
4.1 Dry nitrogen, with an oxygen content of less than 10 mg/kg (ppm).
4.2 Dry air or oxygen.
5 Apparatus
5.1 Thermogravimetric analyser.
There are many types of analyser commercially available. All should be suitable for use with this part of
ISO 9924, but their suitability should be checked using the procedure in Clause 6. Calibrate and operate
the thermogravimetric analyser in accordance with the manufacturer’s instructions.
The basic components of an analyser are as follows.
5.1.1 Thermogravimetric balance.
5.1.2 Electrically heated, thermo-regulated oven.
5.1.3 Temperature programmer, for the oven.
5.1.4 Switching device, allowing either a stream of nitrogen or, alternatively, a stream of air or oxygen
to flow through the oven at a predetermined and constant flow rate.
5.1.5 X/Y recorder, for recording the temperature/mass plot. Alternatively, temperature/time and
mass/time plots may be recorded simultaneously using a two-pen Y/T recorder. Digital data acquisition
stations with related software for drawing the temperature/mass and/or time/mass curves are also
suitable; in this case, better accuracy in the calculation of the mass losses can be achieved.
5.1.6 Auxiliary equipment for producing differential curves (mandatory for this part of ISO 9924).
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ISO 9924-2:2016(E)

5.1.7 Analytical balance, capable of weighing to 0,1 mg.
6 Thermogravimetric analyser checks
6.1 Measurement of purge time, t
p
6.1.1 Place a test portion of carbon black or black-filled rubber, as specified in the manufacturer’s
instructions, in the thermobalance sample pan and heat to 650 °C in a stream of nitrogen, at the maximum
rate allowed by the temperature programmer.
6.1.2 Maintaining the temperature at 650 °C, introduce air or oxygen and allow the test portion to
combust fully.
6.1.3 When there is no further mass change, switch off the oven heater and allow the oven to cool to
room temperature, maintaining the air or oxygen flow. At this point, the oven will have been thoroughly
purged with air or oxygen. The following operations are designed to determine the time, t , required to
p
completely restore the inert atmosphere of nitrogen.
6.1.4 With the oven at 25 °C ± 5 °C, introduce a fresh test portion of carbon black, of mass as specified
in the manufacturer’s instructions, into the balance pan and close the apparatus.
6.1.5 Record the time, t , switch over to nitrogen gas flow, set the oven temperature to increase to
1
650 °C at a rate of 10 °C/min and then hold the temperature constant.
6.1.6 Observe the thermogravimetric analyser mass trace and, when this no longer indicates a mass
loss with time, note the time, t .
2
As a check, the pan should still contain carbon black since the mass loss should be constant if not all the
carbon black has burned off during the heating time.
6.1.7 The purge time, t , which is the time required to purge all oxygen from the system, is given by
p
Formula (1):
t = t – t (1)
p 2 1
6.2 Discrimination between carbon black and calcium carbonate
6.2.1 Calcium carbonate will decompose to calcium oxide when heated to 800 °C. Carbon black is
thermally stable up to this temperature in a nitrogen atmosphere. In air or oxygen, however, carbon black
will be oxidized to carbon dioxide at 800 °C.
6.2.2 Provided that nitrogen having a low enough concentration of oxygen is used, that purging
is carried out for a time greater than the purge time determined in 6.1, that there are no leaks in the
apparatus, and that the oven design and gas flow rate ensure that all carbon dioxide is swept out from the
sample chamber, there should be no problem in distinguishing between, and measuring separately, black
and whiting (calcium carbonate). To check the operation of the thermogravimetric analyser, carry out the
following
...