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

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Status
Published
Publication Date
20-Jan-2022
Current Stage
5060 - Close of voting Proof returned by Secretariat
Completion Date
22-Dec-2021
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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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© 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.
© 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.
© 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: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© 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.
© 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.
© 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
...

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