Raw rubber and rubber latex — Determination of the glass transition temperature by differential scanning calorimetry (DSC)

This document specifies a method using a differential scanning calorimeter to determine the glass transition temperature of raw rubber and rubber latex.

Caoutchouc et latex de caoutchouc brut — Détermination de la température de transition vitreuse par analyse calorimétrique différentielle (DSC)

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Status
Published
Publication Date
07-Jul-2020
Current Stage
6060 - International Standard published
Start Date
08-Jul-2020
Completion Date
08-Jul-2020
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INTERNATIONAL ISO
STANDARD 22768
Third edition
2020-07
Raw rubber and rubber latex —
Determination of the glass transition
temperature by differential scanning
calorimetry (DSC)
Caoutchouc et latex de caoutchouc brut — Détermination de la
température de transition vitreuse par analyse calorimétrique
différentielle (DSC)
Reference number
ISO 22768:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 22768:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

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
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 22768:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 2

5 Apparatus and materials.............................................................................................................................................................................. 2

6 Preparation of the test sample ............................................................................................................................................................... 2

6.1 Raw rubber ................................................................................................................................................................................................. 2

6.2 Rubber latex .............................................................................................................................................................................................. 2

7 Conditioning .............................................................................................................................................................................................................. 2

8 Calibration .................................................................................................................................................................................................................. 2

9 Procedure..................................................................................................................................................................................................................... 3

9.1 Gas flow rate .............................................................................................................................................................................................. 3

9.2 Loading the test specimen ............................................................................................................................................................ 3

9.3 Temperature scan ................................................................................................................................................................................. 3

10 Expression of results ........................................................................................................................................................................................ 3

11 Test report ................................................................................................................................................................................................................... 4

12 Precision ....................................................................................................................................................................................................................... 5

Annex A (informative) Precision on raw rubber ...................................................................................................................................... 6

Annex B (informative) Precision on rubber latex ................................................................................................................................... 9

Bibliography .............................................................................................................................................................................................................................11

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 22768:2020(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 Technical Committee ISO/TC 45, Rubber and rubber products,

Subcommittee SC 3, Raw materials (including latex) for use in the rubber industry.

This third edition cancels and replaces the second edition (ISO 22768:2017), which has been technically

revised.
The main changes compared to the previous edition are as follows:
— rubber latex has been added to the scope and to Clause 6 as 6.2;
— a new Annex B on the precision of rubber latex has been added.

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 2020 – All rights reserved
---------------------- Page: 4 ----------------------
INTERNATIONAL STANDARD ISO 22768:2020(E)
Raw rubber and rubber latex — Determination of the
glass transition temperature by differential scanning
calorimetry (DSC)

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.

1 Scope

This document specifies a method using a differential scanning calorimeter to determine the glass

transition temperature of raw rubber and rubber latex.
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 124:2014, Latex, rubber — Determination of total solids content
ISO 1407, Rubber — Determination of solvent extract

ISO 11357-1:2016, Plastics — Differential scanning calorimetry (DSC) — Part 1: General principles

ISO 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test methods

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 11357-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
glass transition

reversible change in an amorphous polymer, or in amorphous regions of a partially crystalline polymer,

from (or to) a rubbery or viscous condition to (or from) a glassy or hard condition

3.2
glass transition temperature

approximate midpoint of the temperature range over which glass transition (3.1) takes place

Note 1 to entry: For the purposes of this document, the glass transition temperature is defined as the point of

inflection of the DSC curve which has been obtained at a heating rate of 20 °C/min (see A.3).

© ISO 2020 – All rights reserved 1
---------------------- Page: 5 ----------------------
ISO 22768:2020(E)
4 Principle

The change in specific heat capacity of the test sample as a function of temperature under a specified

inert atmosphere is measured using a differential scanning calorimeter (DSC). The glass transition

temperature is determined from the curve thus produced.
5 Apparatus and materials
5.1 Differential scanning calorimeter, in accordance with ISO 11357-1:2016, 5.1.

The calorimeter should be operated in a room held at standard laboratory temperature. It should be

protected from draughts, direct sunlight and sudden temperature changes.
5.2 Specimen pans (crucibles), in accordance with ISO 11357-1:2016, 5.2.
5.3 Gas supply, analytical grade, usually nitrogen or helium.
5.4 Balance, capable of measuring the specimen mass to an accuracy of ±0,1 mg.
5.5 Oven, capable of being maintained at 105 °C ± 5 °C.
6 Preparation of the test sample
6.1 Raw rubber

The test specimen shall be as representative as possible of the sample being examined and shall have a

mass between 0,01 g and 0,02 g.
To determine T of polymers, extract raw rubber in accordance with ISO 1407.
6.2 Rubber latex

Dry rubber latex samples at 105 °C± 5 °C in accordance with ISO 124:2014, 6.2. Remove the rubber latex

film and cut into pieces about 2 mm × 2 mm.
7 Conditioning

Condition the sample to be examined and the test specimen in accordance with ISO 23529.

8 Calibration
Calibrate the calorimeter according to the manufacturer's instructions.

The use of suitable analytical grade substances is recommended to check the accuracy of the

temperature scale. Ideally, substances whose melting points bracket the temperature range of interest

should be chosen. n-Octane, n-heptane and cyclohexane have been found to be useful. Indium should be

used if a higher temperature calibrant is required.
2 © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 22768:2020(E)
9 Procedure
9.1 Gas flow rate

The same inert gas flow rate with a tolerance of ±10 %, shall be used throughout the procedure. Flow

rates between 10 ml/min and 100 ml/min have been found to be suitable.
9.2 Loading the test specimen

Determine the mass of the test specimen to an accuracy of ±0,1 mg. Unless otherwise specified in the

materials standard, use a mass between 5 mg and 20 mg. The same nominal mass shall be used for all

determinations. If possible, the specimen shall have a flat surface so as to give good thermal contact

with the bottom of the pan.

NOTE 1 Intimate thermal contact between the test specimen and the bottom of the pan is essential for good

repeatability.

Place the specimen in the pan, using tweezers and seal with a lid. Place the sealed pan in the calorimeter

using tweezers.
Do not handle the test specimen or the pan with bare hands.

NOTE 2 Placing an empty pan with a lid as a reference helps to obtain stable DSC thermograms.

9.3 Temperature scan

9.3.1 Cool the test specimen to a temperature of approximately −140 °C at a rate of 10 °C/min or 20 °C/

min and hold at this temperature for 1 min to 10 min until the baseline becomes stable.

A starting temperature of −140 °C is required for the determination of rubbers and rubber latices with

very low glass transition temperatures, e.g. high-cis polybutadiene. For rubbers and rubber latices with

higher glass transitions, this temperature is not necessary.
A starting temperature should be chosen so that a stable base line is achieved b
...

DRAFT INTERNATIONAL STANDARD
ISO/DIS 22768
ISO/TC 45/SC 3 Secretariat: AFNOR
Voting begins on: Voting terminates on:
2020-01-13 2020-04-06
Raw rubber and rubber latex — Determination of the
glass transition temperature by differential scanning
calorimetry (DSC)

Caoutchouc et latex de caoutchouc brut — Détermination de la température de transition vitreuse par

analyse calorimétrique différentielle (DSC)
ICS: 83.040.10; 83.060
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
This document is circulated as received from the committee secretariat.
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 22768:2020(E)
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 SUPPORTING DOCUMENTATION. ISO 2020
---------------------- Page: 1 ----------------------
ISO/DIS 22768:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

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
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/DIS 22768:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 2

5 Apparatus and materials.............................................................................................................................................................................. 2

6 Preparation of the test sample ............................................................................................................................................................... 2

6.1 Raw rubber ................................................................................................................................................................................................. 2

6.2 Rubber latex .............................................................................................................................................................................................. 2

7 Conditioning .............................................................................................................................................................................................................. 2

8 Calibration .................................................................................................................................................................................................................. 2

9 Procedure..................................................................................................................................................................................................................... 2

9.1 Gas flow rate .............................................................................................................................................................................................. 2

9.2 Loading the test specimen ............................................................................................................................................................ 3

9.3 Temperature scan ................................................................................................................................................................................. 3

10 Expression of results ........................................................................................................................................................................................ 3

11 Test report ................................................................................................................................................................................................................... 4

12 Precision ....................................................................................................................................................................................................................... 5

Annex A (informative) Precision on raw rubber ...................................................................................................................................... 6

Annex B (informative) Precision on rubber latex ................................................................................................................................... 9

Bibliography .............................................................................................................................................................................................................................11

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/DIS 22768:2020(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 on 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 the following

URL: 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 third edition cancels and replaces the second edition (ISO 22768:2017), which has been technically

revised with the following changes:

— addition of rubber latex to the scope and preparation of the test sample (6.2);

— addition of precision of rubber latex in a new 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 © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
DRAFT INTERNATIONAL STANDARD ISO/DIS 22768:2020(E)
Raw rubber and rubber latex — Determination of the
glass transition temperature by differential scanning
calorimetry (DSC)

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.

1 Scope

This document specifies a method using a differential scanning calorimeter to determine the glass

transition temperature of raw rubber and rubber latex.
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 124:2014, Latex, rubber — Determination of total solids content
ISO 1407, Rubber — Determination of solvent extract

ISO 11357‑1:2016, Plastics — Differential scanning calorimetry (DSC) — Part 1: General principles

ISO 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test methods

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 11357‑1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
glass transition

reversible change in an amorphous polymer, or in amorphous regions of a partially crystalline polymer,

from (or to) a rubbery or viscous condition to (or from) a glassy or hard condition

3.2
glass transition temperature

approximate midpoint of the temperature range over which the glass transition (3.1) takes place

Note 1 to entry: For the purposes of this document, the glass transition temperature is defined as the point of

inflection of the DSC curve which has been obtained at a heating rate of 20 °C/min (see A.3).

© ISO 2020 – All rights reserved 1
---------------------- Page: 5 ----------------------
ISO/DIS 22768:2020(E)
4 Principle

The change in specific heat capacity of the test sample as a function of temperature under a specified

inert atmosphere is measured using a differential scanning calorimeter (DSC). The glass transition

temperature is determined from the curve thus produced.
5 Apparatus and materials
5.1 Differential scanning calorimeter, in accordance with ISO 11357‑1:2016, 5.1.

The calorimeter should be operated in a room held at standard laboratory temperature. It should be

protected from draughts, direct sunlight and sudden temperature changes.
5.2 Specimen pans (crucibles), in accordance with ISO 11357‑1:2016, 5.2.
5.3 Gas supply, analytical grade, usually nitrogen or helium.
5.4 Balance, capable of measuring the specimen mass to an accuracy of ±0,1 mg.
5.5 Oven, capable of being maintained at 105 °C±5 °C.
6 Preparation of the test sample
6.1 Raw rubber

The test specimen shall be as representative as possible of the sample being examined and shall have a

mass between 0,01 g and 0,02 g.
To determine T of polymers, extract raw rubber in accordance with ISO 1407.
6.2 Rubber latex

Dry rubber latex samples at 105 °C ± 5 °C in accordance with ISO 124:2014, 6.2. Remove the rubber

latex film and cut into pieces about 2 mm × 2 mm.
7 Conditioning

Condition the sample to be examined and the test specimen in accordance with ISO 23529.

8 Calibration
Calibrate the calorimeter according to the manufacturer's instructions.

The use of suitable analytical grade substances is recommended to check the accuracy of the

temperature scale. Ideally, substances whose melting points bracket the temperature range of interest

should be chosen. n-Octane, n‑heptane and cyclohexane have been found to be useful. Indium should be

used if a higher temperature calibrant is required.
9 Procedure
9.1 Gas flow rate

The same inert gas flow rate with a tolerance of ±10 %, shall be used throughout the procedure. Flow

rates between 10 ml/min and 100 ml/min have been found to be suitable.
2 © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
ISO/DIS 22768:2020(E)
9.2 Loading the test specimen

Determine the mass of the test specimen to an accuracy of ±0,1 mg. Unless otherwise specified in the

materials standard, use a mass between 5 mg and 20 mg.The same nominal mass shall be used for all

determinations. If possible, the specimen shall have a flat surface so as to give good thermal contact

with the bottom of the pan.

NOTE 1 Intimate thermal contact between the test specimen and the bottom of the pan is essential for good

repeatability.

Place the specimen in the pan, using tweezers and seal with a lid. Place the sealed pan in the calorimeter

using tweezers.
Do not handle the test specimen or the pan with bare hands.

NOTE 2 Placing an empty pan with a lid as a reference helps to obtain stable DSC thermograms.

9.3 Temperature scan
9.3.1 Cool the test specimen to a temperature of approximately −140 °C at a
...

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