ISO 7781:2001

Styrene-butadiene rubber, raw — Determination of soap and organic-acid content

Caoutchouc butadiène-styrène brut — Détermination de la teneur en savons et acides organiques

General Information

• Status: Withdrawn
• Publication Date: 05-Dec-2001
• Withdrawal Date: 05-Dec-2001
• ICS: 83.040.10 - Latex and raw rubber
• Technical Committee: ISO/TC 45/SC 2 - Testing and analysis
• Drafting Committee: ISO/TC 45/SC 2 - Testing and analysis
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 20-Mar-2008

Relations

• Revised: ISO 7781:2008 - Styrene-butadiene rubber, raw — Determination of soap and organic-acid content
• Effective Date: 15-Apr-2008
• Revises: ISO 7781:1996 - Rubber, raw styrene-butadiene — Determination of soap and organic-acid content
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 7781
Third edition
2001-12-01

Styrene-butadiene rubber, raw —
Determination of soap and organic-acid
content
Caoutchouc butadiène-styrène brut — Détermination de la teneur en
savons et acides organiques




Reference number
ISO 7781:2001(E)
©
ISO 2001

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ISO 7781:2001(E)
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ISO 7781:2001(E)
Contents Page
Foreword.iv
1 Scope .1
2 Normative references.1
3 Principle.1
4 Reagents.2
5 Apparatus .2
6 Sampling and sample preparation.3
7 Procedure .3
8 Expression of results .4
9 Test report .5
Annex A (informative) Test for rosin .6

© ISO 2001 – All rights reserved iii

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ISO 7781:2001(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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 7781 was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 2,
Testing and analyses.
This third edition cancels and replaces the second edition (ISO 7781:1996), which has been technically revised.
Annex A of this International Standard is for information only.
iv © ISO 2001 – All rights reserved

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INTERNATIONAL STANDARD ISO 7781:2001(E)

Styrene-butadiene rubber, raw — Determination of soap
and organic-acid content
WARNING — Persons using this International Standard should be familiar with normal laboratory practice.
This standard 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
This International Standard specifies methods for the determination of the soap and organic-acid content of raw
styrene-butadiene rubber (SBR). Method A is suitable for non-oil-extended styrene-butadiene rubbers. Method B is
applicable to oil-extended styrene-butadiene rubbers.
The methods depend on the extraction of the organic acids and soaps from the rubber by means of a specified
solvent. In practice, therefore, it is convenient to determine both organic-acid and soap contents on separate
portions of the same solvent extract. Since the soaps and organic acids present in the rubber are not single
chemical compounds, the method gives only an approximate value for the soap and organic-acid content.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 385-1:1984, Laboratory glassware — Burettes — Part 1: General requirements
ISO 648:1977, Laboratory glassware — One-mark pipettes
ISO 1042:1998, Laboratory glassware — One-mark volumetric flasks
ISO 1795:2000, Rubber, raw natural and raw synthetic — Sampling and further preparative procedures
ISO 4799:1978, Laboratory glassware — Condensers
3 Principle
A weighed test portion of the rubber, in the form of thin strips, is extracted by ethanol-toluene azeotrope, or, for
alum-coagulated rubber, ethanol-toluene-water mixture. After making up to a standard volume, an aliquot portion of
the extract is withdrawn and titrated with standard acid for the determination of soap and with standard alkali for the
determination of organic acid.
© ISO 2001 – All rights reserved 1

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ISO 7781:2001(E)
4 Reagents
During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent
purity. Use commercially available analytical-grade buffer solutions of known pH or, in the absence of commercial
buffer solutions, prepare the solutions required (4.6, 4.7 and 4.8).
4.1 Ethanol-toluene azeotrope (ETA).
Mix 7 volumes of absolute ethanol with 3 volumes of toluene. Alternatively, mix 7 volumes of commercial-grade
ethanol with 3 volumes of toluene, and boil the mixture with anhydrous calcium oxide (quicklime) under reflux for
4 h. Cool to room temperature and decant through No. 42 filter paper.
4.2 Ethanol-toluene-water mixture.
3 3
Mix 95 cm of ETA (4.1) and 5 cm of water.
3
4.3 Sodium hydroxide solution, c(NaOH) = 0,1 mol/dm , accurately standardized.
4.4 Thymol blue indicator.
3 3 3
Dissolve 0,06 g of thymol blue in 6,45 cm of 0,02 mol/dm sodium hydroxide solution and dilute to 50 cm with
water.
3
4.5 Hydrochloric acid, c(HCl) = 0,05 mol/dm , accurately standardized.
4.6 Buffer solution of nominal pH 7.
Dissolve 3,40 g of potassium dihydrogen phosphate (KH PO ) and 3,55 g of disodium hydrogen phosphate
2 4
3
(Na HPO ) in water and make up to 1 000 cm in a volumetric flas
...