ISO 21490:2022

Rubber and rubber products — Determination of 2-mercaptobenzothiazole content by high performance liquid chromatography (HPLC)

This document specifies a quantitative test method to determine the 2-mercaptobenzothiazole content in rubber and rubber products by high performance liquid chromatography (HPLC). This document delivers a method for quantifying 2-mercaptobenzothiazole in rubber products for a better selection of curing conditions. This document provides a method to follow the curing of rubber with sulfur- and benzothiazole-based accelerators using a chemical measurement which is complementary to the classical rheometric technique.

Caoutchouc et produits à base de caoutchouc — Détermination de la teneur en 2-mercaptobenzothiazole par chromatographie en phase liquide haute performance

General Information

• Status: Published
• Publication Date: 20-Jan-2022
• ICS: 83.060 - Rubber
• Technical Committee: ISO/TC 45/SC 2 - Testing and analysis
• Drafting Committee: ISO/TC 45/SC 2/WG 5 - Chemical tests
• Current Stage: 6060 - International Standard published
• Start Date: 21-Jan-2022
• Completion Date: 21-Jan-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 21490
First edition
2022-01
Rubber and rubber
products — Determination of
2-mercaptobenzothiazole content
by high performance liquid
chromatography (HPLC)
Caoutchouc et produits à base de caoutchouc — Détermination de la
teneur en 2-mercaptobenzothiazole par chromatographie en phase
liquide haute performance
Reference number
ISO 21490:2022(E)
© ISO 2022

---------------------- Page: 1 ----------------------
ISO 21490:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2022 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 21490:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents and materials . 1
6 Apparatus . 2
7 Sampling . 2
8 Procedure .2
8.1 Sample preparation . 2
8.2 Chromatographic conditions . 3
8.3 Preparation of standard working solutions and the calibration curve . 3
8.4 HPLC-DAD testing . 3
9 Test results . . 3
9.1 Calibration curve . 3
9.2 Calculation . 4
10 Precision . 4
11 Test report . 4
Annex A (informative) Schematic chemical reactions during curing or rubber with
sulfenamide that gives 2-MBT . 5
Annex B (informative) A gradient programme of HPLC . 6
Annex C (informative) Calibration . 7
Annex D (informative) Spectrum and chromatogram of 2-MBT . 9
Annex E (informative) Precision .11
Bibliography .12
iii
© ISO 2022 – All rights reserved

---------------------- Page: 3 ----------------------
ISO 21490:2022(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 of the voluntary nature of standards, 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
www.iso.org/iso/foreword.html.
This document was prepared by ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing
and analysis.
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 2022 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 21490:2022(E)
Introduction
2-Mercaptobenzothiazole (sometimes also referred to as: MBT; 2-MBT; 2-benzothiazolethione, or BTSH)
is used in the rubber industry as a curing agent. MBT is in the group of thiazoles and is considered as
scorch fast when used as a primary accelerator.
2-Mercaptobenzothiazole as the acidic sulfur accelerator is widely used in rubber materials because of
its good characteristics: stable sulfides, good vulcanization, and a low critical temperature to accelerate
vulcanization so that the rubber product can reach higher tensile strength and hardness levels.
Measuring 2-mercaptobenzothiazole concentration in rubber compounds at different stages of curing
the rubber product is an excellent means to define the optimal curing conditions of temperature and
time in order to obtain the right properties for the products at the best cost.
During the curing of rubber compounds sulfenamides are used as accelerators, which chemically
react at an early stage of the curing to produce 2-mercaptobenzothiazole and other species.
2-Mercaptobenzothiazole then contributes to the initiation of the mechanism which creates the sulfur
crosslinks between the rubber macromolecules at the end (an example is given in Figure A.1). To ensure
continuous progress, it is important to know the chemical mechanisms involved at each stage. Thus,
it is necessary to quantify the content of 2-mercaptobenzothiazole during the decomposition of the
sulfenamide and to know whether 2-mercaptobenzothiazole has disappeared in any further chemical
reactions.
v
© ISO 2022 – All rights reserved

---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 21490:2022(E)
Rubber and rubber products — Determination of
2-mercaptobenzothiazole content by high performance
liquid chromatography (HPLC)
1 Scope
This document specifies a quantitative test method to determine the 2-mercaptobenzothiazole content
in rubber and rubber products by high performance liquid chromatography (HPLC).
This document delivers a method for quantifying 2-mercaptobenzothiazole in rubber products for a
better selection of curing conditions.
This document provides a method to follow the curing of rubber with sulfur- and benzothiazole-
based accelerators using a chemical measurement which is complementary to the classical rheometric
technique.
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 3696, Water for analytical laboratory use — Specification and test methods
ISO 4661-2, Rubber, vulcanized — Preparation of samples and test
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 21490
ISO/TC 45/SC 2
Rubber and rubber
Secretariat: JISC
products — Determination of
Voting begins on:
2021-10-26 2-mercaptobenzothiazole content
by high performance liquid
Voting terminates on:
2021-12-21
chromatography (HPLC)
Caoutchouc et produits à base de caoutchouc — Détermination de la
teneur en 2-mercaptobenzothiazole par chromatographie en phase
liquide haute performance
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 21490:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2021

---------------------- Page: 1 ----------------------
ISO/FDIS 21490:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2021 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/FDIS 21490:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents and materials . 1
6 Apparatus . 2
7 Sampling . 2
8 Procedure .2
8.1 Sample preparation . 2
8.2 Chromatographic conditions . 3
8.3 Preparation of standard working solutions and the calibration curve . 3
8.4 HPLC-DAD testing . 3
9 Test results . . 3
9.1 Calibration curve . 3
9.2 Calculation . 4
10 Precision . 4
11 Test report . 4
Annex A (informative) Schematic chemical reactions during curing or rubber with
sulfenamide that gives 2-MBT . 5
Annex B (informative) A gradient programme of HPLC . 6
Annex C (informative) Calibration . 7
Annex D (informative) Spectrum and chromatogram of 2-MBT . 9
Annex E (informative) Precision .11
Bibliography .12
iii
© ISO 2021 – All rights reserved

---------------------- Page: 3 ----------------------
ISO/FDIS 21490:2021(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 of the voluntary nature of standards, 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
www.iso.org/iso/foreword.html.
This document was prepared by ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing
and analysis.
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 2021 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/FDIS 21490:2021(E)
Introduction
2-Mercaptobenzothiazole (sometimes also referred to as: MBT; 2-MBT; 2-benzothiazolethione, or BTSH)
is used in the rubber industry as a curing agent. MBT is in the group of thiazoles and is considered as
scorch fast when used as a primary accelerator.
2-Mercaptobenzothiazole as the acidic sulfur accelerator is widely used in rubber materials because of
its good characteristics: stable sulfides, good vulcanization, and a low critical temperature to accelerate
vulcanization so that the rubber product can reach higher tensile strength and hardness levels.
Measuring 2-mercaptobenzothiazole concentration in rubber compounds at different stages of curing
the rubber product is an excellent means to define the optimal curing conditions of temperature and
time in order to obtain the right properties for the products at the best cost.
During the curing of rubber compounds sulfenamides are used as accelerators, which chemically
react at an early stage of the curing to produce 2-mercaptobenzothiazole and other species.
2-Mercaptobenzothiazole then contributes to the initiation of the mechanism which creates the sulfur
crosslinks between the rubber macromolecules at the end (an example is given in Figure A). To ensure
continuous progress, it is important to know the chemical mechanisms involved at each stage. Thus,
it is necessary to quantify the content of 2-mercaptobenzothiazole during the decomposition of the
sulfenamide and to know whether 2-mercaptobenzothiazole has disappeared in any further chemical
reactions.
v
© ISO 2021 – All rights reserved

---------------------- Page: 5 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 21490:2021(E)
Rubber and rubber products — Determination of
2-mercaptobenzothiazole content by high performance
liquid chromatography (HPLC)
1 Scope
This document specifies a quantitative test method to determine the 2-mercaptobenzothiazole content
in rubber and rubber products by high performance liquid chromatography (HPLC).
This document delivers a method for quantifying 2-mercaptobenzothiazole in rubber products for a
better selection of curing conditions.
This document provides a method to follow the curing of rubber with sulfur- and benzothiazole-
based accelerators using a chemical measurement which is complementary to the classical rheometric
technique.
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 referenc
...