ISO 248-2:2019

Rubber, raw — Determination of volatile-matter content — Part 2: Thermogravimetric methods using an automatic analyser with an infrared drying unit

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.

Caoutchouc brut — Détermination des matières volatiles — Partie 2: Méthodes thermogravimétriques utilisant un analyseur automatique avec une unité de séchage infrarouge

General Information

• Status: Published
• Publication Date: 25-Mar-2019
• ICS: 83.040.10 - Latex and raw rubber
• Technical Committee: ISO/TC 45/SC 3 - Raw materials (including latex) for use in the rubber industry
• Drafting Committee: ISO/TC 45/SC 3/WG 5 - Synthetic and reclaimed rubber
• Current Stage: 6060 - International Standard published
• Start Date: 26-Mar-2019
• Completion Date: 26-Mar-2019

RELATIONS

• Replaces: ISO 248-2:2012 - Rubber, raw — Determination of volatile-matter content — Part 2: Thermogravimetric methods using an automatic analyser with an infrared drying unit
• Effective Date: 31-Mar-2018

Standards Content (sample)

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 248-2:2019(E)
ISO 2019
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ISO 248-2:2019(E)
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© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

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ii © ISO 2019 – All rights reserved
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ISO 248-2:2019(E)
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

© ISO 2019 – All rights reserved iii
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ISO 248-2:2019(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).

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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 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 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
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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 2019 – All rights reserved 1
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ISO 248-2:2019(E)

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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 =×100 (1)
rel
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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