ISO 248-2:2019

INTERNATIONAL ISO
STANDARD 248-2
Second edition
2019-03
Rubber, raw — Determination of
volatile-matter content —
Part 2:
Thermogravimetric methods using an
automatic analyser with an infrared
drying unit
Caoutchouc brut — Détermination des matières volatiles —
Partie 2: Méthodes thermogravimétriques utilisant un analyseur
automatique avec une unité de séchage infrarouge
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Reagents . 2
6 Apparatus . 2
6.1 Automatic analyser . 2
7 Sampling and preparation of test portion . 2
8 Procedure. 3
8.1 General . 3
8.2 Determination of endpoints for method A and method B . 3
8.3 Method A (pre-defined drying time method) . 4
8.4 Method B (in which drying ends when the mass loss rate has decreased to a pre-
defined level) . 5
8.5 Calculation of volatile-matter content . 5
9 Precision . 6
10 Test report . 6
Annex A (informative) Examples of test conditions . 7
Annex B (informative) Precision data . 8
Bibliography .10
Foreword
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different types of ISO documents should be noted. This document was drafted in accordance with the
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.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 248-2:2012), which has been technically
revised.
The main change compared to the previous edition is the addition of precision data for isoprene rubber
in Table B.2, following an additional ITP conducted by Japan in 2017.
A list of all parts in the ISO 248 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.
iv © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 248-2:2019(E)
Rubber, raw — Determination of volatile-matter content —
Part 2:
Thermogravimetric methods using an automatic analyser
with an infrared drying unit
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 — Some procedures specified in this document could 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
1.1 This document specifies two thermogravimetric methods for the determination of moisture and
other volatile-matter content in raw rubbers by using an automatic analyser with an infrared drying unit.
1.2 These methods are applicable to the determination of volatile-matter content in synthetic rubbers
(SBR, NBR, BR, IR, CR, IIR, halogenated IIR and EPDM) listed in ISO 1629 and to various forms of raw
rubber, such as bale, block, chip, pellet, crumb, powder and sheet. These methods might also be applicable
to other raw rubbers only when the change in mass is proven to be due solely to loss of original volatile
matter and not to rubber degradation.
1.3 The methods are not applicable to raw rubbers which need homogenizing as specified in ISO 1795.
1.4 The hot-mill method and the oven method specified in ISO 248-1 and the methods specified in this
document might not give identical results. In cases of dispute, therefore, the oven method, procedure A,
specified in ISO 248-1:2011, is the referee method.
NOTE These methods can be useful for routine determinations, e.g. quality control, when the measurement
conditions for the automatic analyser are fixed for a particular raw rubber or grade of raw rubber.
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 248-1, Rubber, raw — Determination of volatile-matter content — Part 1: Hot-mill method and
oven method
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 https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Principle
A test portion is continuously weighed to constant mass by a thermogravimetric method using an
automatic analyser with infrared drying. The volatile-matter content is calculated as the mass lost
during this procedure.
5 Reagents
Use only reagents of recognized analytical grade and only distilled water or water of equivalent purity.
5.1 Sodium l-tartrate dihydrate, purity ≥99 %, for use as a standard reference material.
6 Apparatus
Use ordinary laboratory apparatus and the following.
6.1 Automatic analyser
The automatic analyser shall consist of the following components:
a) an infrared drying unit or a far-infrared drying unit or a near-infrared drying unit;
b) a balance, capable of weighing to the nearest 1 mg;
c) a microprocessor, capable of controlling drying conditions such as the temperature and the drying
end point, and of continuously calculating volatile-matter content as the mass lost during drying.
The accuracy of the system shall be demonstrated by performing 10 successive determinations on the
standard reference material sodium l-tartrate dihydrate (5.1). The mean of the 10 determinations shall
be (15,66 ± 0,5) %. The relative standard deviation, obtained by Formula (1), shall be less than 1,0 %.
S
s =×100 (1)
rel
W
where
s is the relative standard deviation, in percentage;
rel
S is the standard deviation;
W is the mean volatile-matter content, in mass %.
7 Sampling and preparation of test portion
Take a laboratory sample in accordance with the method specified in ISO 1795, and then prepare a
test portion of between 2 g and 15 g from the laboratory sample. The actual mass of the test portion
depends on the type of analyser, the expected volatile-matter content, and the form of the sample.
For raw rubbers in bale form, the test portion shall be cut into small pieces of volume less than abo
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