ISO 12492:2025
(Main)Rubber, raw — Determination of water content by Karl Fischer method
Rubber, raw — Determination of water content by Karl Fischer method
This document specifies two test methods for the determination of water content of raw rubber and compounded rubber using a coulometric Karl Fischer titration method: — method A uses an evaporator of heating tube type oven; — method B uses an evaporator of vial type oven. It applies to the water content range between 0,01 % and 1 %. In case of dispute, method B is the preferred method.
Caoutchouc brut — Détermination de la teneur en eau par la méthode de Karl Fischer
General Information
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Standards Content (Sample)
International
Standard
ISO 12492
Second edition
Rubber, raw — Determination of
2025-06
water content by Karl Fischer method
Caoutchouc brut — Détermination de la teneur en eau par la
méthode de Karl Fischer
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 3
7 Calibration . 5
8 Sampling and preparation of test piece. 5
9 Procedure . 6
9.1 Method A .6
9.1.1 Power on .6
9.1.2 Selection of the generator electrode .6
9.1.3 Filling the electrolysis cell .6
9.1.4 Equipment check .6
9.1.5 Analysis .7
9.2 Method B .8
9.2.1 Preparation of apparatus . .8
9.2.2 Checking the instrument .8
9.2.3 Determination .8
10 Expression of results . 9
10.1 Method A .9
10.2 Method B .9
11 Precision . 10
12 Test report . 10
Annex A (normative) Calibration schedule .11
Annex B (informative) Precision .12
Bibliography .13
iii
Foreword
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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 12492:2012), which has been technically
revised.
The main changes are as follows:
— addition of a new method B using a vial type oven in the Scope (Clause 1);
— addition of water standard KF-oven in 5.2;
— addition of a coulometric Karl Fischer titrator with an evaporator of vial type oven in 6.2 and sample
vials in 6.6;
— addition of the procedure of method B in 9.2;
— addition of the expression of results in Clause 10;
— addition of the precision data in Annex B.
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
Introduction
The water content of raw rubber is one of the important characteristics to be determined as a quality
control test. Different synthetic rubbers contain varying amounts of water. Water can affect product quality,
texture, shelf life, chemical stability and reactivity. A high amount of water can cause processing difficulties.
Water contamination is a cause for major concern in a large number of applications. In the rubber industry,
water is one of the major damaging contaminants and is often overlooked as a primary cause of component
failure. For certain applications in the rubber industry, even a small amount of water can have damaging
effects on production.
Several methods are available for the determination of water content. A Karl Fischer (KF) coulometric
titrator is one of the most accurate methods. Unlike other techniques, it can trace low levels of free,
emulsified and dissolved water (which cannot be detected with normal gravimetric methods). The test is
capable of measuring water levels as low as 0,01 %.
Unlike gravimetric measurements, which are indirect methods that assume that all volatiles removed are
water, the Karl Fischer titration is a direct method that is almost specific for water. The method is especially
useful for low moisture levels (< 1 %).
The new test method can help determine the water content of the raw rubber and rubber compounds in the
shortest possible time and can be helpful for quality control in laboratories. Coulometric determination of
water is an absolute method.
v
International Standard ISO 12492:2025(en)
Rubber, raw — Determination of water content by Karl
Fischer 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 can 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 two test methods for the determination of water content of raw rubber and
compounded rubber using a coulometric Karl Fischer titration method:
— method A uses an evaporator of heating tube type oven;
— method B uses an evaporator of vial type oven.
It applies to the water content range between 0,01 % and 1 %.
In case of dispute, method B is the preferred method.
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 1795, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
ISO 18899, Rubber — Guide to the calibration of test equipment
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Principle
The water determination test (Karl Fischer method) is designed to determine the water content in
substances, utilizing the quantitative reaction of water with iodine and sulfur dioxide in the presence of a
lower alcohol such as methanol and an organic base, as shown in the following formulae:
−
H O + I + SO + 3 RN → 2(RN+H)I + RN·SO
2 2 2 3
RN·SO + CH OH → (RN+H)O-SO ·OCH .
3 3 2 3
There are two determination methods which differ in the way the iodine is provided: the volumetric titration
method and the coulometric titration method.
In the volumetric titration method, the iodine r
...
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