Plastics - Determination of thermal conductivity and thermal diffusivity - Part 2: Transient plane heat source (hot disc) method (ISO 22007-2:2015)

This part of ISO 22007 specifies a method for the determination of the thermal conductivity and
thermal diffusivity, and hence the specific heat capacity per unit volume of plastics. The experimental
arrangement can be designed to match different specimen sizes. Measurements can be made in gaseous
and vacuum environments at a range of temperatures and pressures.
This method is suitable for testing homogeneous and isotropic materials, as well as anisotropic materials
with a uniaxial structure. The homogeneity of the material extends throughout the specimen and no
thermal barriers (except those next to the probe) are present within a range defined by the probing
depth(s) (see 3.2 below).
The method is suitable for materials having values of thermal conductivity, λ, in the approximate
range 0,010 W⋅m−1⋅K−1 < λ < 500 W⋅m−1⋅K−1, values of thermal diffusivity, α, in the range
5 × 10−8 m2⋅s−1 < α < 10−4 m2⋅s−1, and for temperatures, T, in the approximate range 50 K < T < 1 000 K.
NOTE 1 The specific heat capacity per unit volume, C, can be obtained by dividing the thermal conductivity, λ,
by the thermal diffusivity, α, i.e. C = λ/α, and is in the approximate range 0,005 MJ⋅m−3⋅K−1 < C < 5 MJ⋅m−3⋅K−1. It is
also referred to as the volumetric heat capacity.
NOTE 2 If the intention is to determine the thermal resistance or the apparent thermal conductivity in the
through-thickness direction of an inhomogeneous product (for instance a fabricated panel) or an inhomogeneous
slab of a material, reference is made to ISO 8301, ISO 8302, and ISO 472.
The thermal-transport properties of liquids can also be determined, provided care is taken to minimize
thermal convection.

Kunststoffe - Bestimmung der Wärmeleitfähigkeit und der Temperaturleitfähigkeit - Teil 2: Transientes Flächenquellenverfahren (Hot-Disk-Verfahren) (ISO 22007-2:2015)

Plastiques - Détermination de la conductivité thermique et de la diffusivité thermique - Partie 2: Méthode de la source plane transitoire (disque chaud) (ISO 22007-2:2015)

ISO 22007-2:2015 spécifie une méthode pour déterminer la conductivité thermique et la diffusivité thermique, et de ce fait la capacité calorifique spécifique par unité de volume, des plastiques. Le dispositif expérimental peut être conçu pour s'accorder à différentes tailles d'éprouvette. Les mesurages peuvent être effectués dans des environnements gazeux et sous vide sur une plage de températures et de pressions.

Polimerni materiali - Ugotavljanje toplotne prevodnosti in toplotne razprševalnosti - 2. del: Metoda s tranzientnim ploskovnim toplotnim virom (vroči disk) (ISO 22007-2:2015)

Ta del standarda ISO 22007 določa metodo za ugotavljanje toplotne prevodnosti in
toplotne razprševalnosti ter posledično specifične toplotne kapacitete polimernih materialov na enoto prostornine. Eksperimentalna ureditev je lahko oblikovana tako, da ustreza različnim velikostim vzorca. Meritve je mogoče opravljati v plinskem in vakuumskem okolju pri različni temperaturi in tlaku.
Ta metoda je primerna za preskušanje homogenih in izotropnih materialov ter anizotropnih materialov z enoosno strukturo. Homogenost materiala se razteza po celotnem vzorcu in ni prisotnih toplotnih pregrad (razen poleg sonde) v območju, opredeljenem z globino sondiranja (glej 3.2 spodaj).
Metoda je primerna za materiale z vrednostmi toplotne prevodnosti, λ, v približnem območju 0,010 W⋅m−1⋅K−1 < λ < 500 W⋅m−1⋅K−1, vrednostmi toplotne razprševalnosti, α, v območju 5 × 10−8 m2⋅s−1 < α < 10−4 m2⋅s−1 in temperatur, T, v približnem območju 50 K < T < 1 000 K.
OPOMBA 1: Specifično toplotno kapaciteto na enoto prostornine, C, je mogoče pridobiti z deljenjem toplotne prevodnosti, λ, s toplotno razprševalnostjo, α, tj. C = λ/α, pri čemer je ta količnik v približnem območju 0,005 MJ⋅m−3⋅K−1 < C < 5 MJ⋅m−3⋅K−1. Zanj se uporablja tudi izraz prostorninska toplotna kapaciteta.
OPOMBA 2: Če želite ugotoviti toplotno upornost ali dejansko toplotno prevodnost nehomogenega izdelka v smeri skozi debelino (na primer izdelane plošče) ali nehomogene plošče iz enega materiala, upoštevajte standarde ISO 8301, ISO 8302 in ISO 472.
Ugotoviti je mogoče tudi lastnosti toplotnega prenosa za tekočine, vendar je treba posebej paziti na zmanjšanje toplotne konvekcije.

General Information

Status
Withdrawn
Public Enquiry End Date
10-Aug-2014
Publication Date
08-Sep-2015
Withdrawal Date
10-Jul-2022
Current Stage
9900 - Withdrawal (Adopted Project)
Start Date
08-Jul-2022
Due Date
31-Jul-2022
Completion Date
11-Jul-2022

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Plastics - Determination of thermal conductivity and thermal diffusivity - Part 2: Transient

plane heat source (hot disc) method (ISO 22007-2:2015)

Kunststoffe - Bestimmung der Wärmeleitfähigkeit und der Temperaturleitfähigkeit - Teil 2:

Transientes Flächenquellenverfahren (Hot-Disk-Verfahren) (ISO 22007-2:2015)

Plastiques - Détermination de la conductivité thermique et de la diffusivité thermique -

Partie 2: Méthode de la source plane transitoire (disque chaud) (ISO 22007-2:2015)

Ta slovenski standard je istoveten z: EN ISO 22007-2:2015
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
SIST EN ISO 22007-2:2015 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 22007-2:2015
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SIST EN ISO 22007-2:2015
EUROPEAN STANDARD
EN ISO 22007-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2015
ICS 83.080.01 Supersedes EN ISO 22007-2:2012
English Version
Plastics - Determination of thermal conductivity and thermal
diffusivity - Part 2: Transient plane heat source (hot disc) method
(ISO 22007-2:2015)

Plastiques - Détermination de la conductivité thermique et Kunststoffe - Bestimmung der Wärmeleitfähigkeit und der

de la diffusivité thermique - Partie 2: Méthode de la source Temperaturleitfähigkeit - Teil 2: Transientes

plane transitoire (disque chaud) (ISO 22007-2:2015) Flächenquellenverfahren (Hot-Disk-Verfahren) (ISO 22007-

2:2015)
This European Standard was approved by CEN on 20 June 2015.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European

Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national

standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same

status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United

Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2015 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 22007-2:2015 E

worldwide for CEN national Members.
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SIST EN ISO 22007-2:2015
EN ISO 22007-2:2015 (E)
Contents Page

European foreword .............................................................................................................................................3

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SIST EN ISO 22007-2:2015
EN ISO 22007-2:2015 (E)
European foreword

This document (EN ISO 22007-2:2015) has been prepared by Technical Committee ISO/TC 61 "Plastics" in

collaboration with Technical Committee CEN/TC 249 “Plastics” the secretariat of which is held by NBN.

This European Standard shall be given the status of a national standard, either by publication of an identical

text or by endorsement, at the latest by February 2016, and conflicting national standards shall be withdrawn

at the latest by February 2016.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 22007-2:2012.

According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following

countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech

Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,

Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,

Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

Endorsement notice

The text of ISO 22007-2:2015 has been approved by CEN as EN ISO 22007-2:2015 without any modification.

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SIST EN ISO 22007-2:2015
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SIST EN ISO 22007-2:2015
INTERNATIONAL ISO
STANDARD 22007-2
Second edition
2015-08-01
Plastics — Determination of thermal
conductivity and thermal diffusivity —
Part 2:
Transient plane heat source (hot disc)
method
Plastiques — Détermination de la conductivité thermique et de la
diffusivité thermique —
Partie 2: Méthode de la source plane transitoire (disque chaud)
Reference number
ISO 22007-2:2015(E)
ISO 2015
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2015, Published in Switzerland

All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2015 – All rights reserved
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(E)
Contents Page

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

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

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

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

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

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

5 Apparatus ..................................................................................................................................................................................................................... 3

6 Test specimens........................................................................................................................................................................................................ 5

6.1 Bulk specimens ....................................................................................................................................................................................... 5

6.2 Anisotropic bulk specimens ........................................................................................................................................................ 6

6.3 Slab specimens ........................................................................................................................................................................................ 6

6.4 Thin-film specimens ........................................................................................................................................................................... 7

7 Procedure..................................................................................................................................................................................................................... 7

8 Calculation of thermal properties ...................................................................................................................................................... 9

8.1 Bulk specimens ....................................................................................................................................................................................... 9

8.2 Anisotropic bulk specimens .....................................................................................................................................................12

8.3 Slab specimens .....................................................................................................................................................................................13

8.4 Thin-film specimens ........................................................................................................................................................................14

8.5 Low thermally conducting specimens .............................................................................................................................15

8.5.1 Introductory remarks ...............................................................................................................................................15

8.5.2 Low thermally conducting bulk specimens ...........................................................................................15

8.5.3 Low thermally conducting anisotropic bulk specimens .............................................................17

8.5.4 Low thermally conducting thin–film specimen ................................................................................17

9 Calibration and verification ...................................................................................................................................................................17

9.1 Calibration of apparatus ..............................................................................................................................................................17

9.2 Verification of apparatus .............................................................................................................................................................18

10 Precision and bias ............................................................................................................................................................................................18

11 Test report ................................................................................................................................................................................................................19

Bibliography .............................................................................................................................................................................................................................20

© ISO 2015 – All rights reserved iii
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(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 meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers

to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 61, Plastics, Subcommittee SC 5, Physical-

chemical properties.

This second edition cancels and replaces the first edition (ISO 22007-2:2008), which has been technically

revised.
The main changes are the following:
a) Values of thermal conductivity in scope revised;
b) Sensitivity coefficient revised (3.3);
c) Thickness range for thin-film specimens changed (6.4);
d) Low thermally conducting specimens specified (8.5);
e) Precision and bias adapted; (10.2);
f) Bibliography extended;
g) Normative references updated and standard editorial revised.

ISO 22007 consists of the following parts, under the general title Plastics — Determination of thermal

conductivity and thermal diffusivity:
— Part 1: General principles
— Part 2: Transient plane heat source (hot disc) method
— Part 3: Temperature wave analysis method
— Part 4: Laser flash method

— Part 5: Results of interlaboratory testing of poly(methyl methacrylate) samples [Technical Report]

iv © ISO 2015 – All rights reserved
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(E)

— Part 6: Comparative method for low thermal conductivities using a temperature-modulation technique

© ISO 2015 – All rights reserved v
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(E)
Introduction

A significant increase in the development and application of new and improved materials for broad

ranges of physical, chemical, biological, and medical applications has necessitated better performance

data from methods of measurement of thermal-transport properties. The introduction of alternative

methods that are relatively simple, fast, and of good precision would be of great benefit to the scientific

[1]
and engineering communities.

A number of measurement techniques described as transient methods have been developed and several

have been commercialized. These are being widely used and are suitable for testing many types of

material. In some cases, they can be used to measure several properties separately or simultaneously.

[2],[3]

A further advantage of some of these methods is that it has become possible to measure the true

bulk properties of a material. This feature stems from the possibility of eliminating the influence of

the thermal contact resistance (see 8.1.1) that is present at the interface between the probe and the

[1],[3],[4],[5],[6]
specimen surfaces.
vi © ISO 2015 – All rights reserved
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SIST EN ISO 22007-2:2015
INTERNATIONAL STANDARD ISO 22007-2:2015(E)
Plastics — Determination of thermal conductivity and
thermal diffusivity —
Part 2:
Transient plane heat source (hot disc) method
1 Scope

This part of ISO 22007 specifies a method for the determination of the thermal conductivity and

thermal diffusivity, and hence the specific heat capacity per unit volume of plastics. The experimental

arrangement can be designed to match different specimen sizes. Measurements can be made in gaseous

and vacuum environments at a range of temperatures and pressures.

This method is suitable for testing homogeneous and isotropic materials, as well as anisotropic materials

with a uniaxial structure. The homogeneity of the material extends throughout the specimen and no

thermal barriers (except those next to the probe) are present within a range defined by the probing

depth(s) (see 3.2 below).

The method is suitable for materials having values of thermal conductivity, λ, in the approximate

−1 −1 −1 −1

range 0,010 W⋅m ⋅K < λ < 500 W⋅m ⋅K , values of thermal diffusivity, α, in the range

−8 2 −1 −4 2 −1

5 × 10 m ⋅s < α < 10 m ⋅s , and for temperatures, T, in the approximate range 50 K < T < 1 000 K.

NOTE 1 The specific heat capacity per unit volume, C, can be obtained by dividing the thermal conductivity, λ,

−3 −1 −3 −1

by the thermal diffusivity, α, i.e. C = λ/α, and is in the approximate range 0,005 MJ⋅m ⋅K < C < 5 MJ⋅m ⋅K . It is

also referred to as the volumetric heat capacity.

NOTE 2 If the intention is to determine the thermal resistance or the apparent thermal conductivity in the

through-thickness direction of an inhomogeneous product (for instance a fabricated panel) or an inhomogeneous

slab of a material, reference is made to ISO 8301, ISO 8302, and ISO 472.

The thermal-transport properties of liquids can also be determined, provided care is taken to minimize

thermal convection.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the cited edition applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 22007-1, Plastics — Determination of thermal conductivity and thermal diffusivity — Part 1: General

principles
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 22007-1 and the following

apply.
3.1
penetration depth
pen

measure of how far into the specimen, in the direction of heat flow, a heat wave has travelled

Note 1 to entry: For this method, the penetration depth is given by
© ISO 2015 – All rights reserved 1
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(E)
Δpt=⋅κα
pentot
where
t is the total measurement time for the transient recording;
tot
α is the thermal diffusivity of the specimen material;
κ is a constant dependent on the sensitivity of the temperature recordings.
Note 2 to entry: It is expressed in metres (m).
3.2
probing depth
prob

measure of how far into the specimen, in the direction of heat flow, a heat wave has travelled during the

time window used for calculation
Note 1 to entry: The probing depth is given by
Δpt=⋅κα
prob max
where

t is the maximum time of the time window used for calculating the thermal-transport proper-

max
ties.
Note 2 to entry: It is expressed in metres (m).

Note 3 to entry: A typical value in hot disc measurements is κ = 2, which is assumed throughout this part of

ISO 22007.
3.3
sensitivity coefficient
coefficient defined by the formula
∂Δ Tt 
 
β =q
where

q is the thermal conductivity, λ, the thermal diffusivity, α, or the volumetric specific heat

capacity, C;
ΔT(t) is the mean temperature increase of the probe.

Note 1 to entry: Different sensitivity coefficients are defined for thermal conductivity, thermal diffusivity, and

[7]
specific heat per unit volume.

Note 2 to entry: To define the time window that is used to determine both the thermal conductivity and diffusivity

from one single experiment, the theory of sensitivity coefficients is used. Through this theory, which deals with a

large number of experiments and considers the constants, q, as variables, it has been established that

0,30< t ⋅α/r < 1,0
max
where r is the mean radius of the outermost spiral of the probe.
Assuming κ = 2, this expression can be rewritten as
2 © ISO 2015 – All rights reserved
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(E)
1,1r < Δp < 2,0r
prob
4 Principle

A specimen containing an embedded hot disc probe of negligible heat capacity is allowed to equilibrate

at a given temperature. A heat pulse in the form of a stepwise function is produced by an electrical

current through the probe to generate a dynamic temperature field within the specimen. The increase

in the temperature of the probe is measured as a function of time. The probe operates as a temperature

sensor unified with a heat source (i.e. a self-heated sensor). The response is then analysed in accordance

with the model developed for the specific probe and the assumed boundary conditions.

5 Apparatus
5.1 A schematic diagram of the apparatus is shown in Figure 1.
Key
1 specimen with probe 5 bridge circuit
2 chamber 6 voltmeter
3 vacuum pump 7 voltage source
4 thermostat 8 computer
Figure 1 — Basic layout of the apparatus

5.2 A typical hot disc probe is shown in Figure 2. Convenient probes can be designed with diameters

from 2 mm to 200 mm, depending on the specimen size and the thermal-transport properties of the

material to be tested. The probe is constructed as a bifilar spiral etched out of a (10 ± 2) µm thick metal

foil and covered on both sides by thin (from 7 µm to 100 µm) insulating film. It is recommended that

nickel or molybdenum be used as the heater/temperature-sensing metal foil due to their relatively

high temperature coefficient of electrical resistivity and stability over a wide temperature range. It is

recommended that polyimide, mica, aluminium nitride, or aluminium oxide be used as the insulating

film, depending on the ultimate temperature of use. The arms of the bifilar spiral forming an essentially

circular probe shall have a width of (0,20 ± 0,03) mm for probes with an overall diameter of 15 mm or

less and a width of (0,35 ± 0,05) mm for probes of larger diameter. The distance between the edges of the

arms shall be the same as the width of the arms.
© ISO 2015 – All rights reserved 3
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(E)
Key
D sensor diameter

NOTE Sensor diameters, from 2 mm to 200 mm can conveniently be used, depending on available specimen

size. The distances indicated in this figure should be measured in any but the same unit of length, when used to

calculate the heat loss through the electrical leads according to Formula (16).
Figure 2 — Hot disc probe with bifilar spiral as heating/sensing element

5.3 An electrical bridge shall be used to record the transient increase in resistance of the probe. Through

the bridge, which is initially balanced, the successive increases in resistance of the probe shall be followed

by recording the imbalance of the bridge with a sensitive voltmeter (see Figure 3). With this arrangement,

the probe is placed in series with a resistor which shall be designed in such a way that its resistance is

kept strictly constant throughout the transient. These two components are combined with a precision

potentiometer, the resistance of which shall be about 100 times larger than the sum of the resistances of

the probe and the series resistor. The bridge shall be connected to a power supply which can supply 20 V

and a current of up to 1 A. The digital voltmeter by which the difference voltages are recorded shall have

a resolution corresponding to 6,5 digits at an integration time of 1 power line cycle. The resistance of the

series resistor, R , shall be close to the initial resistance of the probe with its leads, R + R , in order to

S 0 L

keep the power output of the probe as constant as possible during the measurement.

4 © ISO 2015 – All rights reserved
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(E)
Key
1 potentiometer R total resistance of the probe leads
2 probe R series resistance
3 probe leads R initial resistance of the probe before initiating the
transient heating
ΔR increase in resistance of the probe during the
transient heating
ΔU voltage imbalance created by the increase in the
resistance of the probe

NOTE This experimental arrangement allows the determination of temperature deviations from the iterated

straight line (see treatment of experimental data in 8.1) down to or better than 50 µK.

Figure 3 — Diagram of electrical bridge for recording the resistance increase of the probe

5.4 A constant-temperature environment controlled to ±0,1 K or better for the duration of a

measurement shall be established (see Figure 1). The chamber need only be evacuated when working

with slab specimens (see 6.3).
6 Test specimens
6.1 Bulk specimens

6.1.1 For bulk specimens, the requirement for specimen thickness depends on the thermal properties

of the material from which the specimen is made. The expression for the probing depth contains the

diffusivity, which is not known prior to the measurement. This means that the probing depth has to be

calculated after an initial experiment has been completed. If, with this new information, the probing

depth is found to be outside the limits given in 8.1.3, the test shall be repeated, with an adjusted total

measurement time, until the required conditions are fulfilled.

The shape of the specimen can be cylindrical, square, or rectangular. Machining to a certain shape is not

necessary, as long as a flat surface (see 6.1.4) on each of the two specimen halves faces the sensor and

the requirements regarding sensor size given in 8.1.3 are fulfilled.

6.1.2 The measurement shall be conducted in such a way that the probing depth into the specimen

shall be at least 20 times the characteristic length of the components making up the material or of any

inhomogeneity in the material, e.g. the average diameter of the particles if the specimen is a powder.

6.1.3 The specimen dimensions shall be chosen to minimize the effect that its outer surfaces will have

on the measurement. The specimen size shall be such that the distance from any part of the bifilar spiral

© ISO 2015 – All rights reserved 5
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SIST EN ISO 22007-2:2015
ISO 22007-2:2015(E)

of the hot disc probe to any part of the outside boundary of the specimen is larger than the overall mean

radius of the bifilar spiral (see 5.2). An increase in this distance beyond the size of the diameter of the

spiral does not improve the accuracy of the results.

6.1.4 Specimen surfaces which are in contact with the sensor shall be plane and smooth. The specimen

halves shall be clamped on to both sides of the hot disc probe.
NOTE Heat sink contact paste is not recommended since:

a) it is difficult to obtain a sufficiently thin layer of paste which will actually improve the thermal contact;

b) the paste obviously increases the heat capacity of the insulating layer and delays the development of the

constant temperature difference between the sensing material and the specimen surface;

c) it is difficult to obtain exactly the same thickness of paste on both sides of the probe and achieve a strictly

symmetrical flow of heat from the heating/sensing material through the insulation into the two specimen

halves.

6.1.5 For liquids, suitable containment vessels with adequate seals are necessary and air bubbles and

evaporation shall be avoided.

Storage and conditioning of the liquid can affect its properties, e.g. by absorption of water or gas. It

might be necessary to pre-treat the specimen prior to testing, e.g. by degassing. However, pre-treatment

procedures shall not be used whenever they could detrimentally affect the material to be tested, e.g.

through degradation.

6.1.6 For materials prone to significant dimensional changes whether instigated by measurements

over large temperature ranges, thermal expansion, change of state, phase transition, or other causes, care

shall be taken to ensure that when placing the hot disc probe in contact with the specimen, the applied

load does not affect the properties of the specimen.

With soft materials, the clamping pressure shall not compress the specimen and thus change its thermal-

transport properties.

6.1.7 The specimen shall be conditioned in accordance with the standard specification which applies to

the type of material and its particular use.
6.2 Anisotropic bulk specimens
6.2.1 If a material is anisotropic, specimens shall be cut (
...

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