Plastics — Fast differential scanning calorimetry (FSC) — Chip calorimetry

This document specifies the characteristics of non-adiabatic fast differential scanning calorimeters, also covered by the general abbreviation FSC having an open specimen geometry in which specimens are placed directly onto active measurement areas of chip sensors based on Micro-Electro-Mechanical Systems (MEMS) membrane technology, without encapsulation in closed crucibles and ovens. Due to the open specimen geometry, this document is applicable to very small specimens having masses of not greater than 1 µg only. The occurrence of high temperature gradients during measurements can be prevented by keeping specimen thicknesses as small as possible. The use of very low specimen masses enables achievement of very high scanning rates in the order of several thousand K/s, both in heating and cooling mode whereby lower specimen masses and thicknesses allow higher heating and cooling rates. Typically, low scanning rates of FSC overlap with high scanning rates of conventional DSC covered by ISO 11357‑1, thus enabling connection to conventional DSC results. NOTE 1 Due to the sensor layout FSC is also called chip calorimetry. NOTE 2 FSC stands for Fast Scanning Calorimetry but also for Fast Scanning Calorimeter. In practice from the context the choice can be made quite easily. FSC is suitable for thermal analysis of fast kinetic effects of polymers, polymer blends and composites, such as: — thermoplastics (polymers, moulding compounds and other moulding materials, with or without fillers, fibres or reinforcements); — thermosets (uncured or cured materials, with or without fillers, fibres or reinforcements); — elastomers (with or without fillers, fibres or reinforcements). This document specifies methods for qualitative and quantitative analysis of fast physical and chemical processes showing changes in heat flow rate. This includes measurement of characteristic temperatures as well as caloric values of both, solid and liquid materials. This document is particularly applicable for the observation of fast kinetics of thermal effects such as: — physical transitions (glass transition, phase transitions such as melting and crystallization, polymorphic transitions, etc.); — metastability and related processes like reorganization, (re)crystallization, annealing, ageing, amorphization; — chemical reactions (hydration, oxidation, polymerisation, crosslinking and curing of elastomers and thermosets, decomposition, etc.); — isothermal measurements of fast crystallising systems or chemical reactions. It is also applicable for the determination of heat capacity and related changes of thermodynamic functions. FSC provides a technique to analyse material behaviour at similarly high heating or cooling rates used in industrial polymer processing. FSC can also enable separation of overlapping thermal effects with different kinetics such as: — melting and decomposition: higher heating rates can shift decomposition to higher temperatures and allow unperturbed measurement of melting; — glass transition and cold crystallisation of polymers: higher heating rates can suppress cold crystallisation resulting in unperturbed measurement of glass transition as a function of cooling / heating rates; — reorganisation of amorphous or semi-crystalline polymers upon cooling and heating: depending on the cooling rate used specimens with different crystallinities can be generated and their reorganisation upon heating analysed using different scanning rates. This document establishes general aspects of FSC, such as the principle and the apparatus, sampling, calibration and general aspects of the procedure and test report.

Plastiques — Calorimétrie différentielle à balayage rapide (FSC) — Calorimétrie à balayage ultra-rapide

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Publication Date
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INTERNATIONAL ISO
STANDARD 23976
First edition
2021-02
Plastics — Fast differential scanning
calorimetry (FSC) — Chip calorimetry
Plastiques — Calorimétrie différentielle à balayage rapide (FSC) —
Calorimétrie à balayage ultra-rapide
Reference number
ISO 23976:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO 23976:2021(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
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 23976:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

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

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

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Principle ........................................................................................................................................................................................................................ 3

5 Apparatus ..................................................................................................................................................................................................................... 4

5.1 Chip calorimeter .................................................................................................................................................................................... 4

5.2 Microscope ................................................................................................................................................................................................. 5

5.3 Tools for sample preparation ..................................................................................................................................................... 5

5.4 Calibration materials ......................................................................................................................................................................... 5

5.5 Measuring atmosphere .................................................................................................................................................................... 5

6 Specimens .................................................................................................................................................................................................................... 5

7 Test conditions and specimen conditioning ............................................................................................................................ 6

7.1 Test conditions ........................................................................................................................................................................................ 6

7.2 Conditioning of specimens ........................................................................................................................................................... 6

8 Calibration .................................................................................................................................................................................................................. 6

8.1 Chip calorimeter performance .................................................................................................................................................. 6

[14],[17] 8

8.2 Temperature calibration .................................................................................................................................................

8.2.1 General...................................................................................................................................................................................... 8

8.2.2 Correction for thermal lag due to scan rate .............................................................................................. 9

8.2.3 Correction for thermal lag due to sample mass .................................................................................10

8.2.4 Correction of measured temperature extrapolated to zero heating rate .....................10

[14],[17],[21] 12

8.3 Symmetry of temperature calibration .....................................................................................................

8.3.1 General...................................................................................................................................................................................12

8.3.2 Procedure ............................................................................................................................................................................12

8.4 Calibration of heat and heat flow rate..............................................................................................................................13

9 Specimen measurement procedure ..............................................................................................................................................14

9.1 Preparation of apparatus ............................................................................................................................................................14

9.1.1 Starting the instrument...........................................................................................................................................14

9.1.2 Purge gas .................. .................................................... ........................................................................................................14

9.1.3 Preparation of sensor ...............................................................................................................................................14

[23] 14

9.1.4 Blank correction for heat loss ......................................................................................................................

9.2 Placement of specimens on the sensor ...........................................................................................................................15

9.3 Performance of measurements ..............................................................................................................................................16

9.3.1 General...................................................................................................................................................................................16

9.3.2 Running the instrument .........................................................................................................................................17

9.3.3 Reuse of chip sensor ..................................................................................................................................................17

9.3.4 Evaluation of results ..................................................................................................................................................17

10 Investigation of physical-chemical effects ..............................................................................................................................17

10.1 General ........................................................................................................................................................................................................17

10.2 First Order phase transitions ..................................................................................................................................................17

10.3 Chemical reactions............................................................................................................................................................................17

10.4 Glass transitions..................................................................................................................................................................................18

[24]

11 Determination of heat capacity .................................................................................................................................................18

[14],[23]

12 Determination of specimen mass ..................................................................................................................................20

12.1 General ........................................................................................................................................................................................................20

12.2 Determination of specimen mass based on specific heat capacity of material ............................21

© ISO 2021 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 23976:2021(E)

12.3 Determination of specimen mass based on specific heat capacity change at glass

transition ...................................................................................................................................................................................................21

12.4 Determination of specimen mass based on specific enthalpy of fusion .............................................22

12.5 Determination of specimen mass based on specimen dimensions and density .........................23

12.6 Use of FSC reference specimens ............................................................................................................................................23

12.7 Criteria for selection of correct specimen mass ......................................................................................................23

12.7.1 High specimen mass ..................................................................................................................................................23

12.7.2 Low specimen mass ...................................................................................................................................................24

13 Precision and bias ............................................................................................................................................................................................24

14 Test report ................................................................................................................................................................................................................25

Bibliography .............................................................................................................................................................................................................................26

iv © ISO 2021 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 23976:2021(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 Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-

chemical properties.

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 v
---------------------- Page: 5 ----------------------
ISO 23976:2021(E)
Introduction

The development of fast scanning calorimetry (FSC) based on chip sensors with very high sensitivity

using ultrathin SiN membranes was initially driven by the objective to measure thermal properties of

very small amounts of sample such as thin films at very high scan rates in the order of magnitude of

4 [1] [2]

10 K/s . Shortly after, a differential scanning sensor was also introduced . These quasi-adiabatic

calorimeters could be used in heating mode only. The extension of sensors to fast cooling applications

was achieved upon operating at non-adiabatic conditions by using gas as thermally inert cooling agent.

To avoid the concomitantly strong increase of thermal lag with increasing scan rate, the sample mass is

decreased accordingly. Thus, reduction of specimens and heating elements to very small size enabled

sufficient temperature control upon fast cooling, see References [3] to [7]. Due to these developments,

the scan rate operating window of existing commercial DSCs is extended to more than 7 orders in

magnitude.

A break-through was the development of extremely fast-operating chip-calorimeters, see Table 1, based

on Micro-Electromechanical-Systems (MEMS) technology, as described in various publications (see, for

example, References [8], [9] and [10]). Until recently, results using chip calorimeters have been obtained

[11],[12]

by specific equipment located at universities , however, dedicated research has also led to the

development of commercially available FSC instrumentation.

For MEMS-sensor technology, power compensation-based twin-sensor microchip calorimeters,

commonly known as fast scanning calorimetry (FSC), and its capabilities have received a great deal of

[8]

attention in recent years . The reason that FSC has become increasingly popular is because, firstly, in

practice, some physical and chemical processes and processing techniques occur at much higher rates

than achievable using conventional DSC. Secondly, most nano-structures in materials and substances,

including polymers and pharmaceuticals, are in metastable states and these can be studied by FSC.

[8],[13],[14]

Finally, FSC is facilitated by the world-wide availability of the first commercial FSC instrument ,

[15]

followed by an advanced instrument achieving even higher scan rates and higher temperatures .

Thermal history – specifically cooling and heating rates – and sample/product treatment can change

the material behaviour drastically, leading to strongly deviating end properties. The significantly

extended range of achievable scan rates, increased instrument sensitivity and reduced time constant

of MEMS-sensors has resulted in strongly increased capabilities of studying the influence of thermal

history.

This document describes characteristic features of commercially available non-adiabatic FSCs,

calibration procedures and performance of measurements that deviate significantly from those of

conventional DSC outlined in the ISO 11357 series. See Reference [16].
vi © ISO 2021 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 23976:2021(E)
Table 1 — Typical characteristics of some chip calorimeters
Achievable temperature at
Scan rate
constant rate
Purge gas
FSC
K/s °C
a a
heating cooling heating up to cooling down to type ml/min
20 000 5 000 410 40 N 20
Commercial
instrument 20 000 5 000 410 140 N 20
[13],[14],[15],[17]
20 000 5 000 200 -25 He 20
50 000 20 000 950 100 N 20
Commercial
[15]
instrument 2 b
50 000 20 000 950 250 N 20
University instrument 1 000 000 1 000 000 1 000 30 He 0
[8],[11],[12],[16]
1 000 000 1 000 000 1 000 -180 He 0

Cooling rate is determined by the cooling device (temperature difference to base temperature), magnitude of heat flow

rate, environmental conditions such as thermal conductivity of purge gas, etc.
Without cooling accessory.
© ISO 2021 – All rights reserved vii
---------------------- Page: 7 ----------------------
INTERNATIONAL STANDARD ISO 23976:2021(E)
Plastics — Fast differential scanning calorimetry (FSC) —
Chip calorimetry
1 Scope

This document specifies the characteristics of non-adiabatic fast differential scanning calorimeters,

also covered by the general abbreviation FSC having an open specimen geometry in which specimens

are placed directly onto active measurement areas of chip sensors based on Micro-Electro-Mechanical

Systems (MEMS) membrane technology, without encapsulation in closed crucibles and ovens.

Due to the open specimen geometry, this document is applicable to very small specimens having masses

of not greater than 1 µg only. The occurrence of high temperature gradients during measurements can

be prevented by keeping specimen thicknesses as small as possible.

The use of very low specimen masses enables achievement of very high scanning rates in the order

of several thousand K/s, both in heating and cooling mode whereby lower specimen masses and

thicknesses allow higher heating and cooling rates. Typically, low scanning rates of FSC overlap

with high scanning rates of conventional DSC covered by ISO 11357-1, thus enabling connection to

conventional DSC results.
NOTE 1 Due to the sensor layout FSC is also called chip calorimetry.

NOTE 2 FSC stands for Fast Scanning Calorimetry but also for Fast Scanning Calorimeter. In practice from the

context the choice can be made quite easily.

FSC is suitable for thermal analysis of fast kinetic effects of polymers, polymer blends and composites,

such as:

— thermoplastics (polymers, moulding compounds and other moulding materials, with or without

fillers, fibres or reinforcements);

— thermosets (uncured or cured materials, with or without fillers, fibres or reinforcements);

— elastomers (with or without fillers, fibres or reinforcements).

This document specifies methods for qualitative and quantitative analysis of fast physical and chemical

processes showing changes in heat flow rate. This includes measurement of characteristic temperatures

as well as caloric values of both, solid and liquid materials.

This document is particularly applicable for the observation of fast kinetics of thermal effects such as:

— physical transitions (glass transition, phase transitions such as melting and crystallization,

polymorphic transitions, etc.);

— metastability and related processes like reorganization, (re)crystallization, annealing, ageing,

amorphization;

— chemical reactions (hydration, oxidation, polymerisation, crosslinking and curing of elastomers

and thermosets, decomposition, etc.);
— isothermal measurements of fast crystallising systems or chemical reactions.

It is also applicable for the determination of heat capacity and related changes of thermodynamic

functions.

FSC provides a technique to analyse material behaviour at similarly high heating or cooling rates used

in industrial polymer processing.
© ISO 2021 – All rights reserved 1
---------------------- Page: 8 ----------------------
ISO 23976:2021(E)

FSC can also enable separation of overlapping thermal effects with different kinetics such as:

— melting and decomposition: higher heating rates can shift decomposition to higher temperatures

and allow unperturbed measurement of melting;

— glass transition and cold crystallisation of polymers: higher heating rates can suppress cold

crystallisation resulting in unperturbed measurement of glass transition as a function of cooling /

heating rates;

— reorganisation of amorphous or semi-crystalline polymers upon cooling and heating: depending

on the cooling rate used specimens with different crystallinities can be generated and their

reorganisation upon heating analysed using different scanning rates.

This document establishes general aspects of FSC, such as the principle and the apparatus, sampling,

calibration and general aspects of the procedure and test report.
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 11357-1, Plastics — Differential scanning calorimetry (DSC) — Part 1: General principles

ISO 11357-2, Plastics — Differential scanning calorimetry (DSC) — Part 2: Determination of glass transition

temperature and step height

ISO 11357-3, Plastics — Differential scanning calorimetry (DSC) — Part 3: Determination of temperature

and enthalpy of melting and crystallization

ISO 11357-4, Plastics — Differential scanning calorimetry (DSC) — Part 4: Determination of specific heat

capacity

ISO 11357-5, Plastics — Differential scanning calorimetry (DSC) — Part 5: Determination of characteristic

reaction-curve temperatures and times, enthalpy of reaction and degree of conversion

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
chip sensor

symmetric power-compensated sample holder having low addenda heat capacity (3.6) in the order of

nJ/K based on a silicon nitride membrane with a thickness in the µm range

Note 1 to entry: Electronic components for heater and temperature sensor are attached to the membrane. The

sample holder has separate areas for sample and reference specimen onto which specimens are placed directly

and openly in a purge gas environment without encapsulation in crucibles.
2 © ISO 2021 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 23976:2021(E)
3.2
chip calorimetry

non-adiabatic technique in which the difference between the heat flow rate into the sample (3.3) and

reference side of a symmetric chip sensor (3.1) with open specimen geometry is derived as a function of

temperature or time

Note 1 to entry: The temperature difference between sample and reference side of the sensor, both subjected to

the same temperature program, is regulated to almost zero by increasing or decreasing the heating power on

both sides of the sensor while maintaining the controlled temperature program in a specified atmosphere.

Note 2 to entry: The required differential power is measured as a function of temperature or time. Chip

calorimetry enables direct measurement of caloric values and characteristic temperatures.

Note 3 to entry: Information on graphical representation of results can be found in ISO 11357-1.

3.3
sample

small portion of a material taken from a larger quantity of material and intended to be representative

of the whole or to represent a particular section of a manufactured part, such as the skin

3.4
specimen

test piece taken from the sample (3.3) placed on the sample area of the chip sensor (3.1) and analysed

3.5
reference
comparative specimen placed on the reference area of the chip sensor (3.1)
Note 1 to entry: The reference area of the chip sensor is usually left empty.
3.6
addenda heat capacity
additional heat capacity contribution of the sensor not related to the specimen
4 Principle

Very small amounts (typically in the order of 10 ng and not more than 1 µg) of sample and, if applicable,

reference material are placed directly on the corresponding active areas of the chip sensor. The

difference between the heat flow rate into the specimen and that into the reference is measured as

a function of temperature and/or time while specimen and reference are subjected to the same

temperature-controlled programme under a specified atmosphere.

NOTE Suitable heating and cooling rates can vary depending on the characteristics of particular chip

sensors.

Due to the open sample geometry of fast scanning calorimetry the limitation of sample masses to above

indicated values is important to prevent significant temperature gradients in sample and, if applicable,

reference specimens. Figure 1 shows a schematic picture of a typical chip sensor which consists of

two identical siliconnitride/-oxide membranes having lateral dimensions in the mm range or smaller

and a thickness in the µm range or smaller coated with a thin metal layer for improved temperature

distribution that are mounted in a ceramic plate. The sensor layout is symmetrical where both sides,

sample and reference, have identical separate thermal resistance heaters. The temperature is measured

by means of thermocouples arranged symmetrically around the measurement areas of the sample and

reference side, of the chip sensor, respectively. The measurement principle is power-compensation

DSC, i.e. individual heaters are used for sample and reference area. The difference in electrical power

required to maintain both the sample position and the reference position at the same temperature

is recorded against temperature or time, while each position is subjected to the same temperature-

controlled programme. This enables direct measurement of characteristic temperatures and caloric

values of thermal effects.
© ISO 2021 – All rights reserved 3
---------------------- Page: 10 ----------------------
ISO 23976:2021(E)
Key
1 ceramic plate 5 thermocouple
2 silicon frame 6 resistance heater
3 bonding wire 7 metal plate for improved temperature homogeneity
4 siliconnitride/-oxide membrane
[15]
Figure 1 — Example of chip sensor layout
5 Apparatus
5.1 Chip calorimeter
The instrument shall have the following features:

— chip sensor with designated active areas for placement of sample and reference, for measurements

of liquid samples specifically designed sensors may be used;

— capability of generating constant heating and cooling rates up to 1 000 K/s or higher, the upper

scanning rate limit shall be sufficiently high for intended measurements;

— capability to maintain the test temperature constant to within ±0,5 K or less for at least 60 min;

— capability to perform step heating or step cooling measurements;

NOTE 1 Normally, this is achieved by a suitable combination of linear heating or cooling steps and

constant temperature steps.

— capability to provide a controlled static or purging gas environment of the sample holder. When

using continuous purging of the sample holder, the purge gas flow shall be laminar and the flow rate

controllable to within ±10 %;

NOTE 2 The actual gas flow rate depends on the design of the instrument used and the purpose of

measurement.

— capability of generating a temperature range in line with the experimental requirements;

— capability of achieving a heat flow rate range and sensitivity adapted to the designated sample size

range of the chip sensor;

NOTE 3 For a chip sensor designed for specimen masses between 10 ng and 1 µg, typical values of max.

heat flow rate signal and sensitivity are approximately 20 mW and 1 µW, respectively.

— an adequate time constant of the sensor to achieve sufficiently high heating and cooling rates;

— a recording device capable of automatically recording the measured curve of heat flow rate against

temperature and/or time;
4 © ISO 2021 – All rights reserved
---------------------- Page: 11 ----------------------
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 23976
ISO/TC 61/SC 5
Plastics — Fast differential scanning
Secretariat: DIN
calorimetry (FSC) — Chip calorimetry
Voting begins on:
2020­11­17
Voting terminates on:
2021­01­12
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 23976:2020(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 2020
---------------------- Page: 1 ----------------------
ISO/FDIS 23976:2020(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
CH­1214 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/FDIS 23976:2020(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

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

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

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Principle ........................................................................................................................................................................................................................ 3

5 Apparatus ..................................................................................................................................................................................................................... 4

5.1 Chip calorimeter .................................................................................................................................................................................... 4

5.2 Microscope ................................................................................................................................................................................................. 5

5.3 Tools for sample preparation ..................................................................................................................................................... 5

5.4 Calibration materials ......................................................................................................................................................................... 5

5.5 Measuring atmosphere .................................................................................................................................................................... 5

6 Specimens .................................................................................................................................................................................................................... 5

7 Test conditions and specimen conditioning ............................................................................................................................ 6

7.1 Test conditions ........................................................................................................................................................................................ 6

7.2 Conditioning of specimens ........................................................................................................................................................... 6

8 Calibration .................................................................................................................................................................................................................. 6

8.1 Chip calorimeter performance .................................................................................................................................................. 6

[14],[17] 8

8.2 Temperature calibration .................................................................................................................................................

8.2.1 General...................................................................................................................................................................................... 8

8.2.2 Correction for thermal lag due to scan rate .............................................................................................. 9

8.2.3 Correction for thermal lag due to sample mass .................................................................................10

8.2.4 Correction of measured temperature extrapolated to zero heating rate .....................10

[14],[17],[21] 12

8.3 Symmetry of temperature calibration .....................................................................................................

8.3.1 General...................................................................................................................................................................................12

8.3.2 Procedure ............................................................................................................................................................................12

8.4 Calibration of heat and heat flow rate..............................................................................................................................13

9 Specimen measurement procedure ..............................................................................................................................................14

9.1 Preparation of apparatus ............................................................................................................................................................14

9.1.1 Starting the instrument...........................................................................................................................................14

9.1.2 Purge gas .................. .................................................... ........................................................................................................14

9.1.3 Preparation of sensor ...............................................................................................................................................14

[23] 14

9.1.4 Blank correction for heat loss ......................................................................................................................

9.2 Placement of specimens on the sensor ...........................................................................................................................15

9.3 Performance of measurements ..............................................................................................................................................16

9.3.1 General...................................................................................................................................................................................16

9.3.2 Running the instrument .........................................................................................................................................17

9.3.3 Reuse of chip sensor ..................................................................................................................................................17

9.3.4 Evaluation of results ..................................................................................................................................................17

10 Investigation of physical-chemical effects ..............................................................................................................................17

10.1 General ........................................................................................................................................................................................................17

10.2 First Order phase transitions ..................................................................................................................................................17

10.3 Chemical reactions............................................................................................................................................................................17

10.4 Glass transitions..................................................................................................................................................................................18

[24]

11 Determination of heat capacity .................................................................................................................................................18

[14],[23]

12 Determination of specimen mass ..................................................................................................................................20

12.1 General ........................................................................................................................................................................................................20

12.2 Determination of specimen mass based on specific heat capacity of material ............................21

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/FDIS 23976:2020(E)

12.3 Determination of specimen mass based on specific heat capacity change at glass

transition ...................................................................................................................................................................................................21

12.4 Determination of specimen mass based on specific enthalpy of fusion .............................................22

12.5 Determination of specimen mass based on specimen dimensions and density .........................23

12.6 Use of FSC reference specimens ............................................................................................................................................23

12.7 Criteria for selection of correct specimen mass ......................................................................................................23

12.7.1 High specimen mass ..................................................................................................................................................23

12.7.2 Low specimen mass ...................................................................................................................................................24

13 Precision and bias ............................................................................................................................................................................................24

14 Test report ................................................................................................................................................................................................................25

Bibliography .............................................................................................................................................................................................................................26

iv © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 23976:2020(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 non­governmental, 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.

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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 61, Plastics, Subcommittee SC 5, Physical-

chemical properties.

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.
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ISO/FDIS 23976:2020(E)
Introduction

The development of fast scanning calorimetry (FSC) based on chip sensors with very high sensitivity

using ultrathin SiN membranes was initially driven by the objective to measure thermal properties of

very small amounts of sample such as thin films at very high scan rates in the order of magnitude of

4 [1] [2]

10 K/s . Shortly after, a differential scanning sensor was also introduced . These quasi-adiabatic

calorimeters could be used in heating mode only. The extension of sensors to fast cooling applications

was achieved upon operating at non-adiabatic conditions by using gas as thermally inert cooling agent.

To avoid the concomitantly strong increase of thermal lag with increasing scan rate, the sample mass is

decreased accordingly. Thus, reduction of specimens and heating elements to very small size enabled

sufficient temperature control upon fast cooling, see References [3] to.[7]. Due to these developments,

the scan rate operating window of existing commercial DSCs is extended to more than 7 orders in

magnitude.

A break-through was the development of extremely fast-operating chip-calorimeters, see Table 1, based

on Micro-Electromechanical-Systems (MEMS) technology, as described in various publications (see, for

example, References [8], [9] and [10]). Until recently, results using chip calorimeters have been obtained

[11],[12]

by specific equipment located at universities , however, dedicated research has also led to the

development of commercially available FSC instrumentation.

For MEMS-sensor technology, power compensation-based twin-sensor microchip calorimeters,

commonly known as fast scanning calorimetry (FSC), and its capabilities have received a great deal of

[8]

attention in recent years . The reason that FSC has become increasingly popular is because, firstly, in

practice, some physical and chemical processes and processing techniques occur at much higher rates

than achievable using conventional DSC. Secondly, most nano-structures in materials and substances,

including polymers and pharmaceuticals, are in metastable states and these can be studied by FSC.

[8],[13],[14]

Finally, FSC is facilitated by the world-wide availability of the first commercial FSC instrument ,

[15]

followed by an advanced instrument achieving even higher scan rates and higher temperatures .

Thermal history – specifically cooling and heating rates – and sample/product treatment can change

the material behaviour drastically, leading to strongly deviating end properties. The significantly

extended range of achievable scan rates, increased instrument sensitivity and reduced time constant

of MEMS-sensors has resulted in strongly increased capabilities of studying the influence of thermal

history.

This document describes characteristic features of commercially available non-adiabatic FSCs,

calibration procedures and performance of measurements that deviate significantly from those of

conventional DSC outlined in the ISO 11357 series. See Reference [16].
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ISO/FDIS 23976:2020(E)
Table 1 — Typical characteristics of some chip calorimeters
Achievable temperature at
Scan rate
constant rate
Purge gas
FSC
K/s °C
a a
heating cooling heating up to cooling down to type ml/min
20 000 5 000 410 40 N 20
Commercial
instrument 20 000 5 000 410 140 N 20
[13],[14],[15],[17]
20 000 5 000 200 ­25 He 20
50 000 20 000 950 100 N 20
Commercial
[15]
instrument 2 b
50 000 20 000 950 250 N 20
University instrument 1 000 000 1 000 000 1 000 30 He 0
[8],[11],[12],[16]
1 000 000 1 000 000 1 000 ­180 He 0

Cooling rate is determined by the cooling device (temperature difference to base temperature), magnitude of heat flow

rate, environmental conditions such as thermal conductivity of purge gas, etc.
Without cooling accessory.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 23976:2020(E)
Plastics — Fast differential scanning calorimetry (FSC) —
Chip calorimetry
1 Scope

This document specifies the characteristics of non-adiabatic fast differential scanning calorimeters,

also covered by the general abbreviation FSC having an open specimen geometry in which specimens

are placed directly onto active measurement areas of chip sensors based on Micro-Electro-Mechanical

Systems (MEMS) membrane technology, without encapsulation in closed crucibles and ovens.

Due to the open specimen geometry, this document is applicable to very small specimens having masses

of not greater than 1 µg only. The occurrence of high temperature gradients during measurements can

be prevented by keeping specimen thicknesses as small as possible.

The use of very low specimen masses enables achievement of very high scanning rates in the order

of several thousand K/s, both in heating and cooling mode whereby lower specimen masses and

thicknesses allow higher heating and cooling rates. Typically, low scanning rates of FSC overlap

with high scanning rates of conventional DSC covered by ISO 11357-1, thus enabling connection to

conventional DSC results.
NOTE 1 Due to the sensor layout FSC is also called chip calorimetry.

NOTE 2 FSC stands for Fast Scanning Calorimetry but also for Fast Scanning Calorimeter. In practice from the

context the choice can be made quite easily.

FSC is suitable for thermal analysis of fast kinetic effects of polymers, polymer blends and composites,

such as:

— thermoplastics (polymers, moulding compounds and other moulding materials, with or without

fillers, fibres or reinforcements);

— thermosets (uncured or cured materials, with or without fillers, fibres or reinforcements);

— elastomers (with or without fillers, fibres or reinforcements).

This document specifies methods for qualitative and quantitative analysis of fast physical and chemical

processes showing changes in heat flow rate. This includes measurement of characteristic temperatures

as well as caloric values of both, solid and liquid materials.

This document is particularly applicable for the observation of fast kinetics of thermal effects such as:

— physical transitions (glass transition, phase transitions such as melting and crystallization,

polymorphic transitions, etc.);

— metastability and related processes like reorganization, (re)crystallization, annealing, ageing,

amorphization;

— chemical reactions (hydration, oxidation, polymerisation, crosslinking and curing of elastomers

and thermosets, decomposition, etc.);
— isothermal measurements of fast crystallising systems or chemical reactions.

It is also applicable for the determination of heat capacity and related changes of thermodynamic

functions.

FSC provides a technique to analyse material behaviour at similarly high heating or cooling rates used

in industrial polymer processing.
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ISO/FDIS 23976:2020(E)

FSC can also enable separation of overlapping thermal effects with different kinetics such as:

— melting and decomposition: higher heating rates can shift decomposition to higher temperatures

and allow unperturbed measurement of melting;

— glass transition and cold crystallisation of polymers: higher heating rates can suppress cold

crystallisation resulting in unperturbed measurement of glass transition as a function of cooling /

heating rates;

— reorganisation of amorphous or semi-crystalline polymers upon cooling and heating: depending

on the cooling rate used specimens with different crystallinities can be generated and their

reorganisation upon heating analysed using different scanning rates.

This document establishes general aspects of FSC, such as the principle and the apparatus, sampling,

calibration and general aspects of the procedure and test report.
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 11357­1, Plastics — Differential scanning calorimetry (DSC) — Part 1: General principles

ISO 11357­2, Plastics — Differential scanning calorimetry (DSC) — Part 2: Determination of glass transition

temperature and step height

ISO 11357­3, Plastics — Differential scanning calorimetry (DSC) — Part 3: Determination of temperature

and enthalpy of melting and crystallization

ISO 11357­4, Plastics — Differential scanning calorimetry (DSC) — Part 4: Determination of specific heat

capacity

ISO 11357­5, Plastics — Differential scanning calorimetry (DSC) — Part 5: Determination of characteristic

reaction-curve temperatures and times, enthalpy of reaction and degree of conversion

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 11357­1 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
chip sensor

symmetric power-compensated sample holder having low addenda heat capacity (3.6) in the order of

nJ/K based on a silicon nitride membrane with a thickness in the µm range

Note 1 to entry: Electronic components for heater and temperature sensor are attached to the membrane. The

sample holder has separate areas for sample and reference specimen onto which specimens are placed directly

and openly in a purge gas environment without encapsulation in crucibles.
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ISO/FDIS 23976:2020(E)
3.2
chip calorimetry

non-adiabatic technique in which the difference between the heat flow rate into the sample (3.3) and

reference side of a symmetric chip sensor (3.1) with open specimen geometry is derived as a function of

temperature or time

Note 1 to entry: The temperature difference between sample and reference side of the sensor, both subjected to

the same temperature program, is regulated to almost zero by increasing or decreasing the heating power on

both sides of the sensor while maintaining the controlled temperature program in a specified atmosphere.

Note 2 to entry: The required differential power is measured as a function of temperature or time. Chip

calorimetry enables direct measurement of caloric values and characteristic temperatures.

Note 3 to entry: Information on graphical representation of results can be found in ISO 11357-1.

3.3
sample

small portion of a material taken from a larger quantity of material and intended to be representative

of the whole or to represent a particular section of a manufactured part, such as the skin

3.4
specimen

test piece taken from the sample (3.3) placed on the sample area of the chip sensor (3.1) and analysed

3.5
reference
comparative specimen placed on the reference area of the chip sensor (3.1)
Note 1 to entry: The reference area of the chip sensor is usually left empty.
3.6
addenda heat capacity
additional heat capacity contribution of the sensor not related to the specimen
4 Principle

Very small amounts (typically in the order of 10 ng and not more than 1 µg) of sample and, if applicable,

reference material are placed directly on the corresponding active areas of the chip sensor. The

difference between the heat flow rate into the specimen and that into the reference is measured as

a function of temperature and/or time while specimen and reference are subjected to the same

temperature-controlled programme under a specified atmosphere.

NOTE Suitable heating and cooling rates can vary depending on the characteristics of particular chip

sensors.

Due to the open sample geometry of fast scanning calorimetry the limitation of sample masses to above

indicated values is important to prevent significant temperature gradients in sample and, if applicable,

reference specimens. Figure 1 shows a schematic picture of a typical chip sensor which consists of

two identical siliconnitride/-oxide membranes having lateral dimensions in the mm range or smaller

and a thickness in the µm range or smaller coated with a thin metal layer for improved temperature

distribution that are mounted in a ceramic plate. The sensor layout is symmetrical where both sides,

sample and reference, have identical separate thermal resistance heaters. The temperature is measured

by means of thermocouples arranged symmetrically around the measurement areas of the sample and

reference side, of the chip sensor, respectively. The measurement principle is power-compensation

DSC, i.e. individual heaters are used for sample and reference area. The difference in electrical power

required to maintain both the sample position and the reference position at the same temperature

is recorded against temperature or time, while each position is subjected to the same temperature-

controlled programme. This enables direct measurement of characteristic temperatures and caloric

values of thermal effects.
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ISO/FDIS 23976:2020(E)
Key
1 ceramic plate 5 thermocouple
2 silicon frame 6 resistance heater
3 bonding wire 7 metal plate for improved temperature homogeneity
4 siliconnitride/-oxide membrane
[15]
Figure 1 — Example of chip sensor layout
5 Apparatus
5.1 Chip calorimeter
The instrument shall have the following features:

— chip sensor with designated active areas for placement of sample and reference, for measurements

of liquid samples specifically designed sensors may be used;

— capability of generating constant heating and cooling rates up to 1 000 K/s or higher, the upper

scanning rate limit shall be sufficiently high for intended measurements;

— capability to maintain the test temperature constant to within ±0,5 K or less for at least 60 min;

— capability to perform step heating or step cooling measurements;

NOTE 1 Normally, this is achieved by a suitable combination of linear heating or cooling steps and

constant temperature steps.

— capability to provide a controlled static or purging gas environment of the sample holder. When

using continuous purging of the sample holder, the purge gas flow shall be laminar and the flow rate

controllable to within ±10 %;

NOTE 2 The actual gas flow rate depends on the design of the instrument used and the purpose of

measurement.

— capability of generating a temperature range in line with the experimental requirements;

— capability of achieving a heat flow rate range and sensitivity adapted to the designated sample size

...

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