ISO 22007-7:2023

Plastics — Determination of thermal conductivity and thermal diffusivity — Part 7: Transient measurement of thermal effusivity using a plane heat source

This document specifies a method for the determination of the thermal effusivity. This document is applicable to materials with thermal effusivity in the approximate range 40 W⋅s1/2⋅m−2⋅K−1 bn W⋅s1/2⋅m‑2⋅K‑1, and temperatures in the range of 50 K T

Plastiques — Détermination de la conductivité thermique et de la diffusivité thermique — Partie 7: Mesure transitoire de l'effusivité thermique à l'aide d'une source de chaleur plane

General Information

• Status: Published
• Publication Date: 17-Apr-2023
• ICS: 83.080.01 - Plastics in general
• Technical Committee: ISO/TC 61/SC 5 - Physical-chemical properties
• Drafting Committee: ISO/TC 61/SC 5 - Physical-chemical properties
• Current Stage: 6060 - International Standard published
• Start Date: 18-Apr-2023
• Due Date: 11-Sep-2023
• Completion Date: 18-Apr-2023

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 22007-7
First edition
2023-04
Plastics — Determination of thermal
conductivity and thermal diffusivity —
Part 7:
Transient measurement of thermal
effusivity using a plane heat source
Plastiques — Détermination de la conductivité thermique et de la
diffusivité thermique —
Partie 7: Mesure transitoire de l'effusivité thermique à l'aide d'une
source de chaleur plane
Reference number
ISO 22007-7:2023(E)
© ISO 2023

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ISO 22007-7:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
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ISO 22007-7:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Test specimens . 2
6.1 Configuration A: Rod-shaped specimens having a thermal effusivity above
1/2 -2 -1
1 000 W·s ·m ·K . 2
1/2 -2 -1
6.2 Configuration B: Specimens of thermal effusivity below 1 000 W·s ·m ·K
completely embedding the probe . 3
6.3 Specimen preparation . 3
7 Procedure .4
8 Calculation of thermal effusivity . 6
8.1 Computations . 6
8.2 Single-sided setup . 9
9 Verification procedures .9
9.1 Calibration of apparatus . 9
9.2 Verification of apparatus . 9
10 Precision and bias .10
11 Test report .10
Annex A (informative) Example of testing a homogeneous, anisotropic rod .11
Annex B (informative) Example of testing a stacked, anisotropic Rod .14
Bibliography .16
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ISO 22007-7:2023(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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at  www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
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.
A list of all parts in the ISO 22007 series can be found on the ISO website.
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 22007-7:2023(E)
Introduction
[1]-[4]
The developments of so-called transient measurement methods since the 1990’s , has provided the
scientific community with tools capable of quickly and accurately testing thermophysical properties of
[5]-[9]
small- and irregular-shaped specimens .
A regularly-shaped probe (square, rectangle, circle, ellipse, etc.), consisting of a metal heating pattern,
is sandwiched between two pieces of a specimen material. The probe simultaneously functions as
an ohmic heater – providing approximately equal heat production per unit area across its surface –
and also as a resistance thermometer. In experimental configurations discussed in the following,
the thermal effusivity in the normal direction to the probe surface can be estimated from a single
[2]-[4],[9]
experiment .
The specimens that can be tested using this method are homogeneous isotropic specimens and
[10]
homogeneous anisotropic specimens (with uniaxial structure ). The effusivity is obtained for the
bulk of the specimen material, because of the possibility to eliminate the influence from the thermal
contact resistance between the probe sensing metal pattern and the substrate surface.
Some experimental features on testing thermal effusivity with present approach are, first, the ability
to significantly reduce the overall specimen geometry size. Secondly, the normal-direction heat flow
allows for analysing specimen geometries of major industrial importance, for instance, a layered- or
composite structure, with repeated intrinsic geometric features.
One industrial application considered is the TIM-stacked setup, consisting of a repeated structure
incorporating thermal interface material (TIM) layers between solid slabs. The many drawbacks and
uncertainties of testing a single-layer TIM layer applied in alternative measurement approaches, is here
replaced with an experimental stack setup allowing to precisely measure the final application intended
for a specific TIM layer material.
Parameters to consider when testing thermal effusivity in a rod-shaped specimen are: differences in
probe cross-section and rod specimen cross-section. At least a rough estimation on the volumetric
specific heat of the specimen is also advantageous to know, when estimating the probing depth
(important for controlling of the transient experiment). In addition, potential effects of heat losses to
surroundings should also be assessed.
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INTERNATIONAL STANDARD ISO 22007-7:2023(E)
Plastics — Determination of thermal conductivity and
thermal diffusivity —
Part 7:
Transient measurement of thermal effusivity using a plane
heat source
1 Scope
This document specifies a method for the determination of the thermal effusivity.
This document is applicable to materials with thermal effusivity in the approximate range
1/2 −2 −1 1/2 -2 -1
40 W⋅s ⋅m ⋅K < n
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 22007-1, Plastics — Determination of thermal conductivity and thermal diffusivity — Part 1: General
principles
ISO 22007-2, Plastics — Determination of thermal conductivity and thermal diffusivity — Part 2: Transient
plane heat source (hot disc) method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 22007-1, ISO 22007-2 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
thermal effusivity
b
quantity, possible to express in terms of the square root of the product of the material’s bulk thermal
conductivity and volumetric specific heat of a specimen, bc=⋅λρ
p
Note 1 to entry: In its most general form, this is a second-rank tensor property.
Note 2 to entry: The thermal effusivity in the normal direction to the plane of the probe is represented by the
scalar b .
n
1/2 -2 -1
Note 3 to entry: It is expressed in W⋅s ⋅m ⋅K .
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ISO 22007-7:2023(E)
4 Principle
4.1 A specimen with an internally-positioned thermal effusivity probe – assumed to have a negligible
heat capacity – is set to thermally equilibrate at a certain temperature. A measurement is conducted by
applying a single-step heat pulse (generated by Ohmic heating). A temperature field around the probe
develops with time (from the onset of the single-step heat pulse). The temperature increase in the probe
is recorded at different time points.
4.2 The probe represents a combined heater and temperature sensor – which is sometimes referred
to as a self-heated sensor. The temperature vs. time response is then analysed for the model developed
and the assumed boundary conditions. Two principally different configurations are possible for testing
normal-direction thermal effusivity.
4.3 Configuration A: Specimens and an experimental setup designed to allow the heat flow to occur
essentially in a 1-dimensional manner, in the normal direction from the probe, for a comparably long
period of experimental time. It is suitable for small and narrow specimens with a thermal effusivity
1/2 -2 -1
above approximately 1 000 W⋅s ⋅m ⋅K .
4.4 Configuration B: Specimens and an experimental setup designed to allow the heat flow to occur
essentially in a 1-dimensional manner, in the normal direction from the probe, for a comparably short
period of experimental time. It is suitable for large and wide specimens having a thermal effusivity less
1/2 -2 -1
than approximately 1 000 W⋅s ⋅m ⋅K .
5 Apparatus
The measuring apparatus shall be in accordance with ISO 22007-2.
However, the shape of the probe can differ appreciably as long as an even heat distribution across the
probe cross-section area can be established, see 6.1.3 and 6.2.3.
6 Test specimens
6.1 Configuration A: Rod-shaped specimens having a thermal effusivity above
1/2 -2 -1
1 000 W·s ·m ·K
2
6.1.1 Typical specimen geometry is a cross-section area of minimum from approximately 7 mm
2
(corresponding to approximately 3 mm diameter) to a maximum of approximately 1 000 mm . There is
no requirement regarding the exact shape of the cross-section of the rod, as long as this cross-section
geometry is identical along the length of the rod. Advantageous geometries are circular, square or
rectangular-shaped cross-sections. The rod length, which represents the orientation in which the heat
flow occurs during an experiment and in which orientation the thermal effusivity is to be estimated,
is normally selected depending on the thermophysical properties of the material from which the
specimen is made, and a direct connection is made with the probing depth (see Clause 7). While all
examples in Table 1 have a probing depth of 20 mm, the method described in this subclause is capable
of analysing specimens for rod lengths in the approximate range from minimum length around 3 mm to
a maximum length around 100 mm. In case several repeat-structure components make up the material
(see for example Annex B), the rod length should be selected to at least 10 times the repeat-structure
length scale in order to reduce measurement errors and improve stability in the estimated results.
6.1.2 The specimen geometry is adapted to the geometry of the probe heating area. The cross-section
of the rod shall closely resemble the cross-section of the probe heating area. The cross-section of the rod
shall however be large enough to closely, but completely, embed the probe in a way that no part of the
heating elements of the probe is allowed to stick out from the lateral boundary. A margin (or tolerance)
of 0,5 mm to 1 mm is often acceptable between the edge of the probe and the lateral boundary and is
2
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ISO 22007-7:2023(E)
compensated for in computations (see Clause 8). In addition, the rod lengths covered by the present
method are limited to within 20 times the minimum rod cross-section distance.
6.1.3 As probes can be designed to be in different shapes, such as cylindrical, square or rectangular,
the shape of the specimen cross-section shall have similar shape.
6.1.4 In the basic setup, two specimen halves with symmetric rod geometry facing the probe are
assumed. A flat surface (see 6.3.2) on each of the two specimen halves facing the probe is required.
1/2 -2 -1
6.2 Configuration B: Specimens of thermal effusivity below 1 000 W·s ·m ·K
completely embedding the probe
6.2.1 Typical bulk specimen geometry is a cross-section area of minimum from approximately
2
2 000 mm (corresponding to approximately 50 mm diameter) to a maximum of approximately
2
50 000 mm . The thickness of the bulk specimen required, which due to the low thermal effusivity
requirements, is limited depending on the thermophysical properties of the material from which
the specimen is made, and a direct connection is made with the probing depth (see Clause 7). As the
thickness direction represents the orientation of heat flow assumed in the experiment, the thermal
effusivity in the thickness direction is estimated. While the examples in Table 2 have a probing depth
of 4 mm, the specimen thickness for these examples would require a minimum thickness of 4 mm for a
corresponding experiment to be performed. The described method is capable of analysing specimens of
thicknesses in the approximate range from minimum thickness around 3 mm to a maximum thickness
around 30 mm. In case several repeat-structure components make up the material, preferably the
specimen thickness should be selected to at least 10 times the repeat-structure length scale in order to
reduce measurement errors and improve stability in the estimated results.
6.2.2 The specimen geometry is adapted to the geometry of the probe heating area. The cross-section
of the specimen shall completely embed the probe cross-section, and with a margin on each edge that
exceeds the specimen thickness on the sides of the probe, i.e. the cross-section of the specimen in
one direction shall be at least equal to the cross-section of the probe in the same direction plus 2 x
specimen thickness. For example, a probe of 30 mm × 30 mm cross section, and a specimen thickness of
5 mm, requires a specimen cross-section of a minimum 40 mm × 40 mm cross section. Note that in case
a specific probing depth is required to achieve, for instance if according to 6.2.1 a specific thickness
is required to reach at least 10 times the repeat-structure length scale in the thickness direction, the
cross-section of the specimen geometry as well as the geometry of the probe might need to be selected
differently: According to 6.2.3, the minimum cross-section distance across the probe area should be
selected at least 10 times the specimen thickness (assuming near-isotropic specimen conditions), or at
least 30 times the specimen thickness (in case anisotropy may be at hand) – which with the additional
requirement of a margin at each edge results in a different minimum specimen cross-section area.
6.2.3 Probes can be designed to be in different shapes, such as cylindrical, square or rectangular.
However, it should be noted that specimen thickness probed in the experiment will not exceed 1/10 of
the minimum distance across the cross-section of an effusivity probe, and hence the specimen thickness
can be adapted accordingly following the cross-section design of the probe.
6.2.4 In the basic setup, two specimen halves with symmetric setup facing the probe are assumed. A
flat surface (see 6.3.2) on each of the two specimen halves facing the probe is required.
6.2.5 In case in-plane thermal conductivity is estimated to be more than ten times the through-plane
thermal conductivity, the setup in 6.2 should not be used.
6.3 Specimen preparation
NOTE These specimen preparations apply to the setups described in 6.1 or 6.2.
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ISO 22007-7:2023(E)
6.3.1 The specimen should be conditioned in accordance with the standard specification which
applies to the type of material and its particular use.
6.3.2 The specimen surfaces which are in contact with the probe should be plane and smooth. The
specimen halves shall be clamped on to both sides of the effusivity probe.
6.3.3 It is important to consider specimen materials prone to significant dimensional changes –
whether caused by measurements over large temperature ranges, thermal expansion, change of state,
phase transition, or other causes.
6.3.4 Care should be taken to ensure that the applied load does not affect the properties of the
specimen. For instance, for soft specimens tested according to setup 6.2, the clamping pressure should
not compress the specimen and thus change its thermal transport properties.
6.3.5 Heat sink contact paste shall not be used 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.
7 Procedure
7.1 The procedure for performing measurements shall be in accordance with ISO 22007-2, with the
following additional considerations.
7.2 As described in Clause 6, the preparation of specimen is connected directly with the selection of
effusivity probe to be used.
7.3 For rod shaped specimens, it is important to ensure that heat losses to the surroundings can
1/2 -2 -1
be controlled to a minimum. For specimens of thermal effusivity more than 1 000 W⋅s ⋅m ⋅K it is
normally enough with air, vacuum, or styrofoam insulation applied on the lateral surfaces.
7.4 For rod shaped specimens, it is important to ensure a correct measurement time. This is obtained
by ensuring that the probing depth is at least 1/3 of the rod length, but not exceeding the rod length.
A couple of scouting measurement may sometimes be made, in order to find a suitable measurement
time. In case there are repeat components making up the length of the rod, the probing depth into the
specimen shall be at least 10 times the characteristic length of the components making up the material
or of any inhomogeneity in the material, in the direction of the rod axis.
The expression for the normal-direction probing depth is given by Formula (1):
Δpt=2 α (1)
prob n max
where
t
is the maximum time of the time window used for calculating the thermal-transport proper-
max
ties;
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ISO 22007-7:2023(E)
α
is the thermal diffusivity of the specimen material in the normal direction to the probe sur-
n
face.
In case the thermal diffusivity α is not known, the volumetric specific heat capacity of the specimen
n
should be estimated, either from tabulated data or by direct – separate – measurement by an alternative
method, in order to compute the probing depth according to Formula (2):
−1
12/
Δpb=2 tcρ (2)
() ()
prob npmax
7.5 For rod-shaped specimens, the heat pulse power and test time should use Table 1 or a scouting
experiment, as a guideline.
7.6 For rod-shaped specimens, in case the specimen can be considered being anisotropic, and the
timescale for heat to spread across the rod cross-section is considered to be much smaller than the total
experimental test time, the effects of anisotropy can be assumed to not influence the estimation of the
normal-direction thermal effusivity. For an anisotropic homogeneous specimen, where equal heating
can be assumed across the probe position cross-section, the conditions of the 1-dimensional setup can
also be assumed.
7.7 For rod-shaped specimens, the heat losses from lateral surfaces influence the accuracy of the
measurement. Estimated net heat losses at lateral surfaces (if these can be estimated) divided by total
heating power input in the probe, indicate the contribution of the lateral heat losses to the absolute
error of the measurement.
NOTE When making a measurement on a material with a high thermal effusivity, the temperature undergoes
[11]
a rapid increase at the very beginning of the transient followed by a much more gradual increase . The
insulating layer, between which the sensing spiral is sandwiched, causes this rapid increase. It has been shown
both experimentally and in computer simulations that the temperature difference across the insulating layer
becomes constant within a very short time and remains constant throughout the measurement. The reason is
that the total power output, the area of the sensing material and the thickness of the insulating layer are constant
during the test.
7.8 For specimens with a probe totally embedded in the specimen having a thermal effusivity
1/2 -2 -1
below 1 000 W·s ·m ·K , it is important to ensure a correct measurement time. This is obtained
by ensuring that the probing depth is at least 1/3 of the specimen thickness, but not exceeding the
specimen thickness. A couple of scouting measurement may sometimes be made, in order to find a
suitable measurement time. In case there are repeat components making up the thickness, the probing
depth into the specimen shall be at least 10 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. Formulas (1) and (2) can be used to compute the normal-direction probing
depth.
7.9 For specimens with a probe totally embedded in the specimen having a thermal effusivity below
1/2 -2 -1
1 000 W·s ·m ·K , the heat pulse power and test time should use Table 2 or a scouting experiment, as
a guideline.
7.10 For specimens with a probe totally embedded in the specimen having a thermal effusivity below
1/2 -2 -1
1 000 W·s ·m ·K , in case the in-plane thermal conductivity is higher than the through-plane thermal
conductivity, up to 10 times higher than the through-plane thermal conductivity, the normal-direction
probing depth should be controlled to within less than 1/30 of the smallest cross-section width of the
effusivity probe.
7.11 For specimens with a probe totally embedded in the specimen having a thermal effusivity below
1/2 -2 -1
1 000 W·s ·m ·K , the deviation between the experimental temperature response and that predicted
by the 1-dimensional model is increasing with experimental test time – due to side-ways heatflow at
5
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ISO 22007-7:2023(E)
the edge of the effusivity probe. Following outlined procedures, this error can be controlled to within
the specified errors.
7.12 The thermal effusivity shall be reported along with the conditions under which it was measured,
such as temperature and pressure. The cardinal directions of the material and their orientations in
relation to the plane surface of the specimen shall be reported whenever a material is anisotropic.
Table 1 — Summary of recommended experimental parameters for a range of polymer
composites with different thermal effusivities
Material A Material B Material C Material D
Thermal effusivity
4 3 3 3
12/ −−21
18, ⋅10 92, ⋅10 44, ⋅10 13, ⋅10
 
Ws⋅⋅mK⋅
 
Thermal conductivity
170 40 14 1,5
−−11
 
Wm⋅⋅K
 
Specific heat per unit volume
6 6 6 6
−−31
20, ⋅10 21, ⋅10 14, ⋅10 12, ⋅10
 
Jm⋅⋅K
 
Temperature increase in specimen []K 0,3 0,6 0,8 1,6
Measurement time s 1,2 5,3 10 80
[]
Power output []W 0,9 0,4 0,2 0,04
Probing depth mm 20 20 20 20
[]
NOTE Rod cross-section is 10 mm × 10 mm (probe cross-section assumed to be similar), and rod length is 20 mm.
Table 2 — Summary of recommended experimental parameters for two examples of materials
with different thermal effusivities
Polymer Insulating material
Thermal effusivity
2 2
12/ −−21
57, ⋅10 32, ⋅10
 
Ws⋅⋅mK⋅
 
Thermal conductivity
0,19 0,28
−−11
 
Wm⋅⋅K
 
Specific heat per unit volume
6 5
−−31
17, ⋅10 37, ⋅10
 
Jm⋅⋅K
 
Temperature increase in specimen []K 1,4 2,5
Measurement time s 34 5
[]
Power output []W 0,6 1,6
Probing depth mm 4 4
[]
NOTE P
...

2022-11
2023-01-16
ISO/FDIS 22007-7:20222023
ISO TC 61/SC 5/WG 8
Secretariat: DIN
Plastics — Determination of thermal conductivity and thermal diffusivity —
Part 7: Transient measurement of thermal effusivity using a plane heat source

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ISO/FDIS 22007-7:2023(E)
© ISO 20222023
All rights reserved. Unless otherwise specified, or required in the context of its implementation,
no part of this publication may be reproduced or utilized otherwise in any form or by any means,
electronic or mechanical, including photocopying, or posting on the internet or an intranet,
without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii © ISO 2023 – All rights reserved

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ISO/FDIS 22007-7:2023(E)
Contents
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Test specimens . 2
1/2 -2 -1
6.1 Rod-shaped specimens having a thermal effusivity above 1 000 W·s ·m ·K . 2
1/2 -2 -1
6.2 Bulk specimens of thermal effusivity below 1 000 W·s ·m ·K completely
embedding the probe . 3
6.3 Specimen preparation (for the setups described in 6.1 or 6.2) . 3
7 Procedure . 4
8 Calculation of thermal effusivity . 6
8.1 Computations . 6
8.2 Single-sided setup . 8
9 Verification procedures . 8
9.1 Calibration of apparatus . 8
9.2 Verification of apparatus . 9
10 Precision and bias . 9
11 Test report . 9
Annex A (informative) Example of testing a homogeneous, anisotropic rod . 10
Annex B (informative) Example of testing a stacked, anisotropic Rod . 12
Bibliography . 14
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Test specimens . 2
1/2 -2 -1
6.1 Rod-shaped specimens having a thermal effusivity above 1 000 W·s ·m ·K . 2
1/2 -2 -1
6.2 Bulk specimens of thermal effusivity below 1 000 W·s ·m ·K completely
embedding the probe . 3
6.3 Specimen preparation (for the setups described in 6.1 or 6.2) . 3
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ISO/FDIS 22007-7:2023(E)
7 Procedure . 4
8 Calculation of thermal effusivity . 6
8.1 Computations . 6
8.2 Single-sided setup . 8
9 Verification procedures . 8
9.1 Calibration of apparatus . 8
9.2 Verification of apparatus . 9
10 Precision and bias . 9
11 Test report . 9
Annex A (informative) Example of testing a homogeneous, anisotropic rod . 10
Annex B (informative) Example of testing a stacked, anisotropic Rod . 12
Bibliography . 14

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ISO/FDIS 22007-7:2023(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/directiveswww.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/patentswww.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.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 5, Physical-
chemical properties.
A list of all parts in the ISO 22007 series can be found on the ISO website.
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.htmlwww.iso.org/members.html.
© ISO 2023 – All rights reserved v

---------------------- Page: 5 ----------------------
ISO/FDIS 22007-7:2023(E)
Introduction
[1]-[4]
The developments of so-called transient measurement methods since the 1990’s , has provided the
scientific community with tools capable of quickly and accurately testing thermophysical properties of
[5}-{]-[9]
small- and irregular-shaped specimens .
A regularly-shaped probe (square, rectangle, circle, ellipse, etc.), consisting of a metal heating pattern, is
sandwiched between two pieces of a specimen material. The probe simultaneously functions as an
ohmic heater – providing approximately equal heat production per unit area across its surface – and
also as a resistance thermometer. In experimental configurations discussed in the following, the
thermal effusivity in the normal direction to the probe surface can be estimated from a single
[2 ]-[4 ],[9]
experiment - ], [ .
The specimens that can be tested using this method are homogeneous isotropic specimens and
[10]
homogeneous anisotropic specimens (with uniaxial structure ). The effusivity is obtained for the bulk
of the specimen material, because of the possibility to eliminate the influence from the thermal contact
resistance between the probe sensing metal pattern and the substrate surface.
Some experimental features on testing thermal effusivity with present approach are, first, the ability to
significantly reduce the overall specimen geometry size. Secondly, the normal-direction heat flow
allows for analysing specimen geometries of major industrial importance, for instance, a layered- or
composite structure, with repeated intrinsic geometric features.
One industrial application considered is the TIM-stacked setup, consisting of a repeated structure
incorporating thermal interface material (TIM) layers between solid slabs. The many drawbacks and
uncertainties of testing a single-layer TIM layer applied in alternative measurement approaches, is here
replaced with an experimental stack setup allowing to precisely measure the final application intended
for a specific TIM layer material.
Parameters to consider when testing thermal effusivity in a rod-shaped specimen are: differences in
probe cross-section and rod specimen cross-section. Also, atAt least a rough estimation on the
volumetric specific heat of the specimen is also advantageous to know, when estimating the probing
depth (important for controlling of the transient experiment). In addition, potential effects of heat
losses to surroundings should also be assessed.
vi © ISO 2023 – All rights reserved

---------------------- Page: 6 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 22007-7:2023(E)

Plastics — Determination of thermal conductivity and thermal
diffusivity — Part 7: Transient measurement of thermal effusivity
using a plane heat source
1 Scope
This document specifies a method for the determination of the thermal effusivity.
This document is applicable to materials with thermal effusivity in the approximate range
1/2 −2 −1 1/2 -2 -1
40 W⋅s ⋅m ⋅K <𝑏𝑏 < 40 000 < b < 40 000 W⋅s ⋅m ⋅K , and temperatures in the range of 50 K < T
Field Code Changed
𝑛𝑛 n
< 1 000 K.
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 22007-1, Plastics — Determination of thermal conductivity and thermal diffusivity — Part 1: General
principles
ISO 22007-2, Plastics — Determination of thermal conductivity and thermal diffusivity — Part 2:
Transient plane heat source (hot disc) method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 22007-1, ISO 22007-2 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org https://www.electropedia.org/
3.1
thermal effusivity
b
quantity, possible to express in terms of the square root of the product of the material’s bulk thermal
conductivity and volumetric specific heat of a specimen, 𝑏𝑏 = 𝜆𝜆⋅𝜌𝜌𝑐𝑐 bcλρ⋅
�
𝑝𝑝
p
Note 1 to entry: In its most general form, this is a second-rank tensor property.
Note 2 to entry: The thermal effusivity in the normal direction to the plane of the probe is represented by the
scalar b .
n
© ISO 2023 – All rights reserved 1

=

---------------------- Page: 7 ----------------------
ISO/FDIS 22007-7:2023(E)
1/2 -2 -1
Note 3 to entry: It is expressed in W⋅s ⋅m ⋅K .
4 Principle
4.1 A specimen with an internally-positioned thermal effusivity probe – assumed to have a negligible
heat capacity – is set to thermally equilibrate at a certain temperature. A measurement is conducted by
applying a single-step heat pulse (generated by Ohmic heating). A temperature field around the probe
develops with time (from the onset of the single-step heat pulse). The temperature increase in the
probe is recorded at different time points.
4.2 The probe represents a combined heater and temperature sensor – which is sometimes referred to
as a self-heated sensor. The temperature vs. time response is then analysed for the model developed
and the assumed boundary conditions. Two principally different configurations are possible for testing
normal-direction thermal effusivity.
4.3 Configuration A: Specimens and an experimental setup designed to allow the heat flow to occur
essentially in a 1-dimensional manner, in the normal direction from the probe, for a comparably long
period of experimental time. SuitableIt is suitable for small and narrow specimens with a thermal
1/2 -2 -1
effusivity above approximately 1 000 W⋅s ⋅m ⋅K .
4.4 Configuration B: Specimens and an experimental setup designed to allow the heat flow to occur
essentially in a 1-dimensional manner, in the normal direction from the probe, for a comparably short
period of experimental time. SuitableIt is suitable for large and wide specimens having a thermal
1/2 -2 -1
effusivity less than approximately 1 000 W⋅s ⋅m ⋅K .
5 Apparatus
The measuring apparatus shall be in accordance with ISO 22007-2.
However, the shape of the probe can differ appreciably as long as an even heat distribution across the
probe cross-section area can be established, see Clause 6.1.3 and 6.2.3.
6 Test specimens
6.1 Configuration A: Rod-shaped specimens having a thermal effusivity above
1/2 -2 -1
1 000 W·s ·m ·K
2
6.1.1 Typical specimen geometry is a cross-section area of minimum from approximately 7 mm
2
(corresponding to approximately 3 mm diameter) to a maximum of approximately 1 000 mm . There is
no requirement regarding the exact shape of the cross-section of the rod, as long as this cross-section
geometry is identical along the length of the rod. Advantageous geometries are circular, square or
rectangular-shaped cross-sections. The rod length, which represents the orientation in which the heat
flow occurs during an experiment and in which orientation the thermal effusivity is to be estimated, is
normally selected depending on the thermophysical properties of the material from which the
specimen is made, and a direct connection is made with the probing depth (see Clause 7). While all
examples in Table 1 have a probing depth of 20 mm, would require a specimen length of a minimum of
20 mm for a corresponding experiment to be performed, the method described in this subclause is
capable of analysing specimens for rod lengths in the approximate range from minimum length around
3 mm to a maximum length around 100 mm. In case several repeat-structure components make up the
material (see for example Annex B), preferably the rod length should be selected to at least 10 times the
2 © ISO 2023 – All rights reserved

---------------------- Page: 8 ----------------------
ISO/FDIS 22007-7:2023(E)
repeat-structure length scale in order to reduce measurement errors and improve stability in the
estimated results.
6.1.2 The specimen geometry is adapted to the geometry of the probe heating area. The cross-section
of the rod shall closely resemble the cross-section of the probe heating area. The cross-section of the
rod shall however be large enough to closely, but completely, embed the probe in a way that no part of
the heating elements of the probe is allowed to stick out from the lateral boundary. A margin (or
tolerance) of 0,5 mm to 1 mm is often acceptable between the edge of the probe and the lateral
boundary and is compensated for in computations (see Clause 8). In addition, the rod lengths covered
by the present method are limited to within 20 times the minimum rod cross-section distance.
6.1.3 As probes can be designed to be in different shapes, such as cylindrical, square or rectangular,
the shape of the specimen cross-section shall have similar shape.
6.1.4 In the basic setup, two specimen halves with symmetric rod geometry facing the probe are
assumed. A flat surface (see 6.3.2) on each of the two specimen halves facing the probe is required.
1/2 -2 -1
6.2 Configuration B: Specimens of thermal effusivity below 1 000 W·s ·m ·K
completely embedding the probe
6.2.1 Typical bulk specimen geometry is a cross-section area of minimum from approximately
2
2 000 mm (corresponding to approximately 50 mm diameter) to a maximum of approximately
2
50 000 mm . The thickness of the bulk specimen required, which due to the low thermal effusivity
requirements, is limited depending on the thermophysical properties of the material from which the
specimen is made, and a direct connection is made with the probing depth (see Clause 7). As the
thickness direction represents the orientation of heat flow assumed in the experiment, the thermal
effusivity in the thickness direction is estimated. While the examples in Table 2 have a probing depth of
4 mm, the specimen thickness for these examples would require a minimum thickness of 4 mm for a
corresponding experiment to be performed. The described method is capable of analysing specimens of
thicknesses in the approximate range from minimum thickness around 3 mm to a maximum thickness
around 30 mm. In case several repeat-structure components make up the material, preferably the
specimen thickness should be selected to at least 10 times the repeat-structure length scale in order to
reduce measurement errors and improve stability in the estimated results.
6.2.2 The specimen geometry is adapted to the geometry of the probe heating area. The cross-section
of the specimen shall completely embed the probe cross-section, and with a margin on each edge that
exceeds the specimen thickness on the sides of the probe, i.e. the cross-section of the specimen in one
direction shall be at least equal to the cross-section of the probe in the same direction plus 2 x specimen
thickness. For example, a probe of 30 mm x× 30 mm cross section, and a specimen thickness of 5 mm,
requires a specimen cross-section of a minimum 40 mm x× 40 mm cross section. Note that in case a
specific probing depth is required to achieve, for instance if according to 6.2.1 a specific thickness is
required to reach at least 10 times the repeat-structure length scale in the thickness direction, the
cross-section of the specimen geometry as well as the geometry of the probe might need to be selected
differently: According to 6.2.3, the minimum cross-section distance across the probe area should be
selected at least 10 times the specimen thickness (assuming near-isotropic specimen conditions), or at
least 30 times the specimen thickness (in case anisotropy may be at hand) – which with the additional
requirement of a margin at each edge results in a different minimum specimen cross-section area.
6.2.3 Probes can be designed to be in different shapes, such as cylindrical, square or rectangular.
However, it should be noted that specimen thickness probed in the experiment will not exceed 1/10 of
the minimum distance across the cross-section of an effusivity probe, and hence the specimen thickness
can be adapted accordingly following the cross-section design of the probe.
6.2.4 In the basic setup, two specimen halves with symmetric setup facing the probe are assumed. A
flat surface (see 6.3.2) on each of the two specimen halves facing the probe is required.
© ISO 2023 – All rights reserved 3

---------------------- Page: 9 ----------------------
ISO/FDIS 22007-7:2023(E)
6.2.5 In case in-plane thermal conductivity is estimated to be more than ten times the through-plane
thermal conductivity, the setup in 6.2 should not be used.
6.3 Specimen preparation
NOTE These specimen preparations apply to the setups described in 6.1 or 6.2.
6.3.1 The specimen should be conditioned in accordance with the standard specification which
applies to the type of material and its particular use.
6.3.2 The specimen surfaces which are in contact with the probe should be plane and smooth. The
specimen halves shall be clamped on to both sides of the effusivity probe.
6.3.3 It is important to consider specimen materials prone to significant dimensional changes –
whether caused by measurements over large temperature ranges, thermal expansion, change of state,
phase transition, or other causes.
6.3.4 Care should be taken to ensure that the applied load does not affect the properties of the
specimen. For instance, for soft specimens tested according to setup 6.2, the clamping pressure should
not compress the specimen and thus change its thermal transport properties.
6.3.5 Heat sink contact paste shall not be used 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.
7 Procedure
7.1 The procedure for performing measurements shall be in accordance with ISO 22007-2, with the
following additional considerations.
7.2 As described in Clause 6, the preparation of specimen is connected directly with the selection of
effusivity probe to be used.
7.3 For rod shaped specimens, it is important to ensure that heat losses to the surroundings can be
1/2 -2 -1
controlled to a minimum. For specimens of thermal effusivity more than 1 000 W⋅s ⋅m ⋅K it is
normally enough with air, vacuum, or styrofoam insulation applied on the lateral surfaces.
7.4 For rod shaped specimens, it is important to ensure a correct measurement time. This is obtained
by ensuring that the probing depth is at least 1/3 of the rod length, but not exceeding the rod length. A
couple of scouting measurement may sometimes be made, in order to find a suitable measurement time.
In case there are repeat components making up the length of the rod, the probing depth into the
specimen shall be at least 10 times the characteristic length of the components making up the material
or of any inhomogeneity in the material, in the direction of the rod axis.
The expression for the normal-direction probing depth is given by Formula (1):
4 © ISO 2023 – All rights reserved

---------------------- Page: 10 ----------------------
ISO/FDIS 22007-7:2023(E)
Field Code Changed
∆=p 2 α t
∆=p 2 α t (1)
prob n max prob n max
where
 t is the maximum time of the time window used for calculating the thermal-transport
max
properties;
t
Field Code Changed
max
α
 is the thermal diffusivity of the specimen material in the normal direction to the probe
n
surface.
α
Field Code Changed
n
In case the thermal diffusivity is not known, the volumetric specific heat capacity of the specimen
α α Field Code Changed
n n
should be estimated, either from tabulated data or by direct – separate – measurement by an alternative
method, in order to compute the probing depth according to Formula (2):
−1
1⁄2
( )
∆𝑝𝑝 = 2𝑏𝑏 𝑡𝑡 �𝜌𝜌𝑐𝑐� (2)
prob 𝑛𝑛 max 𝑝𝑝
−1
1/2
Field Code Changed
∆=p 2bt( ) ρc (2)
( )
prob npmax
7.5 For rod-shaped specimens, the heat pulse power and test time should use Table 1 or a scouting
experiment, as a guideline.
7.6 For rod-shaped specimens, in case the specimen can be considered being anisotropic, and the
timescale for heat to spread across the rod cross-section is considered to be much smaller than the total
experimental test time, the effects of anisotropy can be assumed to not influence the estimation of the
normal-direction thermal effusivity. For an anisotropic homogeneous specimen, where equal heating
can be assumed across the probe position cross-section, the conditions of the 1-dimensional setup can
also be assumed.
7.7 For rod-shaped specimens, the heat losses from lateral surfaces influence the accuracy of the
measurement. Estimated net heat losses at lateral surfaces (if these can be estimated) divided by total
heating power input in the probe, indicate the contribution of the lateral heat losses to the absolute
error of the measurement.
NOTE When making a measurement on a material with a high thermal effusivity, the temperature undergoes a
[11]
rapid increase at the very beginning of the transient followed by a much more gradual increase . The insulating
layer, between which the sensing spiral is sandwiched, causes this rapid increase. It has been shown both
experimentally and in computer simulations that the temperature difference across the insulating layer becomes
constant within a very short time and remains constant throughout the measurement. The reason is that the total
power output, the area of the sensing material and the thickness of the insulating layer are constant during the
test.
7.8 For specimens with a probe totally embedded in the specimen having a thermal effusivity below
1/2 -2 -1
1 000 W·s ·m ·K , it is important to ensure a correct measurement time. This is obtained by ensuring
that the probing depth is at least 1/3 of the specimen thickness, but not exceeding the specimen
thickness. A couple of scouting measurement may sometimes be made, in order to find a suitable
measurement time. In case there are repeat components making up the thickness, the probing depth
into the specimen shall be at least 10 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 particl
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 22007-7
ISO/TC 61/SC 5
Plastics — Determination of thermal
Secretariat: DIN
conductivity and thermal diffusivity —
Voting begins on:
2023-01-30
Part 7:
Voting terminates on:
Transient measurement of thermal
2023-03-27
effusivity using a plane heat source
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 22007-7:2023(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 2023

---------------------- Page: 1 ----------------------
ISO/FDIS 22007-7:2023(E)
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 22007-7
ISO/TC 61/SC 5
Plastics — Determination of thermal
Secretariat: DIN
conductivity and thermal diffusivity —
Voting begins on:
Part 7:
Voting terminates on:
Transient measurement of thermal
effusivity using a plane heat source
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
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.
RECIPIENTS OF THIS DRAFT ARE INVITED TO
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OF ANY RELEVANT PATENT RIGHTS OF WHICH
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DOCUMENTATION.
Phone: [phone]
IN ADDITION TO THEIR EVALUATION AS
Reference number
Email: [e-mail]
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 22007-7:2023(E)
Website: www.iso.org
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
Published in Switzerland
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
ii
  © ISO 2023 – All rights reserved
NATIONAL REGULATIONS. © ISO 2023

---------------------- Page: 2 ----------------------
ISO/FDIS 22007-7:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Test specimens . 2
6.1 Configuration A: Rod-shaped specimens having a thermal effusivity above
1/2 -2 -1
1 000 W·s ·m ·K . 2
1/2 -2 -1
6.2 Configuration B: Specimens of thermal effusivity below 1 000 W·s ·m ·K
completely embedding the probe . 3
6.3 Specimen preparation . 3
7 Procedure .4
8 Calculation of thermal effusivity . 6
8.1 Computations . 6
8.2 Single-sided setup . 9
9 Verification procedures .9
9.1 Calibration of apparatus . 9
9.2 Verification of apparatus . 9
10 Precision and bias .10
11 Test report .10
Annex A (informative) Example of testing a homogeneous, anisotropic rod .11
Annex B (informative) Example of testing a stacked, anisotropic Rod.14
Bibliography .16
iii
© ISO 2023 – All rights reserved

---------------------- Page: 3 ----------------------
ISO/FDIS 22007-7:2023(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.
A list of all parts in the ISO 22007 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
  © ISO 2023 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/FDIS 22007-7:2023(E)
Introduction
[1]-[4]
The developments of so-called transient measurement methods since the 1990’s , has provided the
scientific community with tools capable of quickly and accurately testing thermophysical properties of
[5]-[9]
small- and irregular-shaped specimens .
A regularly-shaped probe (square, rectangle, circle, ellipse, etc.), consisting of a metal heating pattern,
is sandwiched between two pieces of a specimen material. The probe simultaneously functions as
an ohmic heater – providing approximately equal heat production per unit area across its surface –
and also as a resistance thermometer. In experimental configurations discussed in the following,
the thermal effusivity in the normal direction to the probe surface can be estimated from a single
[2]-[4],[9]
experiment .
The specimens that can be tested using this method are homogeneous isotropic specimens and
[10]
homogeneous anisotropic specimens (with uniaxial structure ). The effusivity is obtained for the
bulk of the specimen material, because of the possibility to eliminate the influence from the thermal
contact resistance between the probe sensing metal pattern and the substrate surface.
Some experimental features on testing thermal effusivity with present approach are, first, the ability
to significantly reduce the overall specimen geometry size. Secondly, the normal-direction heat flow
allows for analysing specimen geometries of major industrial importance, for instance, a layered- or
composite structure, with repeated intrinsic geometric features.
One industrial application considered is the TIM-stacked setup, consisting of a repeated structure
incorporating thermal interface material (TIM) layers between solid slabs. The many drawbacks and
uncertainties of testing a single-layer TIM layer applied in alternative measurement approaches, is here
replaced with an experimental stack setup allowing to precisely measure the final application intended
for a specific TIM layer material.
Parameters to consider when testing thermal effusivity in a rod-shaped specimen are: differences in
probe cross-section and rod specimen cross-section. At least a rough estimation on the volumetric
specific heat of the specimen is also advantageous to know, when estimating the probing depth
(important for controlling of the transient experiment). In addition, potential effects of heat losses to
surroundings should also be assessed.
v
© ISO 2023 – All rights reserved

---------------------- Page: 5 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 22007-7:2023(E)
Plastics — Determination of thermal conductivity and
thermal diffusivity —
Part 7:
Transient measurement of thermal effusivity using a plane
heat source
1 Scope
This document specifies a method for the determination of the thermal effusivity.
This document is applicable to materials with thermal effusivity in the approximate range
1/2 −2 −1 1/2 -2 -1
40 W⋅s ⋅m ⋅K < n
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 22007-1, Plastics — Determination of thermal conductivity and thermal diffusivity — Part 1: General
principles
ISO 22007-2, Plastics — Determination of thermal conductivity and thermal diffusivity — Part 2: Transient
plane heat source (hot disc) method
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 22007-1, ISO 22007-2 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
thermal effusivity
b
quantity, possible to express in terms of the square root of the product of the material’s bulk thermal
conductivity and volumetric specific heat of a specimen, bc=⋅λρ
p
Note 1 to entry: In its most general form, this is a second-rank tensor property.
Note 2 to entry: The thermal effusivity in the normal direction to the plane of the probe is represented by the
scalar b .
n
1/2 -2 -1
Note 3 to entry: It is expressed in W⋅s ⋅m ⋅K .
1
© ISO 2023 – All rights reserved

---------------------- Page: 6 ----------------------
ISO/FDIS 22007-7:2023(E)
4 Principle
4.1 A specimen with an internally-positioned thermal effusivity probe – assumed to have a negligible
heat capacity – is set to thermally equilibrate at a certain temperature. A measurement is conducted by
applying a single-step heat pulse (generated by Ohmic heating). A temperature field around the probe
develops with time (from the onset of the single-step heat pulse). The temperature increase in the probe
is recorded at different time points.
4.2 The probe represents a combined heater and temperature sensor – which is sometimes referred
to as a self-heated sensor. The temperature vs. time response is then analysed for the model developed
and the assumed boundary conditions. Two principally different configurations are possible for testing
normal-direction thermal effusivity.
4.3 Configuration A: Specimens and an experimental setup designed to allow the heat flow to occur
essentially in a 1-dimensional manner, in the normal direction from the probe, for a comparably long
period of experimental time. It is suitable for small and narrow specimens with a thermal effusivity
1/2 -2 -1
above approximately 1 000 W⋅s ⋅m ⋅K .
4.4 Configuration B: Specimens and an experimental setup designed to allow the heat flow to occur
essentially in a 1-dimensional manner, in the normal direction from the probe, for a comparably short
period of experimental time. It is suitable for large and wide specimens having a thermal effusivity less
1/2 -2 -1
than approximately 1 000 W⋅s ⋅m ⋅K .
5 Apparatus
The measuring apparatus shall be in accordance with ISO 22007-2.
However, the shape of the probe can differ appreciably as long as an even heat distribution across the
probe cross-section area can be established, see 6.1.3 and 6.2.3.
6 Test specimens
6.1 Configuration A: Rod-shaped specimens having a thermal effusivity above
1/2 -2 -1
1 000 W·s ·m ·K
2
6.1.1 Typical specimen geometry is a cross-section area of minimum from approximately 7 mm
2
(corresponding to approximately 3 mm diameter) to a maximum of approximately 1 000 mm . There is
no requirement regarding the exact shape of the cross-section of the rod, as long as this cross-section
geometry is identical along the length of the rod. Advantageous geometries are circular, square or
rectangular-shaped cross-sections. The rod length, which represents the orientation in which the heat
flow occurs during an experiment and in which orientation the thermal effusivity is to be estimated,
is normally selected depending on the thermophysical properties of the material from which the
specimen is made, and a direct connection is made with the probing depth (see Clause 7). While all
examples in Table 1 have a probing depth of 20 mm, the method described in this subclause is capable
of analysing specimens for rod lengths in the approximate range from minimum length around 3 mm to
a maximum length around 100 mm. In case several repeat-structure components make up the material
(see for example Annex B), the rod length should be selected to at least 10 times the repeat-structure
length scale in order to reduce measurement errors and improve stability in the estimated results.
6.1.2 The specimen geometry is adapted to the geometry of the probe heating area. The cross-section
of the rod shall closely resemble the cross-section of the probe heating area. The cross-section of the rod
shall however be large enough to closely, but completely, embed the probe in a way that no part of the
heating elements of the probe is allowed to stick out from the lateral boundary. A margin (or tolerance)
of 0,5 mm to 1 mm is often acceptable between the edge of the probe and the lateral boundary and is
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ISO/FDIS 22007-7:2023(E)
compensated for in computations (see Clause 8). In addition, the rod lengths covered by the present
method are limited to within 20 times the minimum rod cross-section distance.
6.1.3 As probes can be designed to be in different shapes, such as cylindrical, square or rectangular,
the shape of the specimen cross-section shall have similar shape.
6.1.4 In the basic setup, two specimen halves with symmetric rod geometry facing the probe are
assumed. A flat surface (see 6.3.2) on each of the two specimen halves facing the probe is required.
1/2 -2 -1
6.2 Configuration B: Specimens of thermal effusivity below 1 000 W·s ·m ·K
completely embedding the probe
6.2.1 Typical bulk specimen geometry is a cross-section area of minimum from approximately
2
2 000 mm (corresponding to approximately 50 mm diameter) to a maximum of approximately
2
50 000 mm . The thickness of the bulk specimen required, which due to the low thermal effusivity
requirements, is limited depending on the thermophysical properties of the material from which
the specimen is made, and a direct connection is made with the probing depth (see Clause 7). As the
thickness direction represents the orientation of heat flow assumed in the experiment, the thermal
effusivity in the thickness direction is estimated. While the examples in Table 2 have a probing depth
of 4 mm, the specimen thickness for these examples would require a minimum thickness of 4 mm for a
corresponding experiment to be performed. The described method is capable of analysing specimens of
thicknesses in the approximate range from minimum thickness around 3 mm to a maximum thickness
around 30 mm. In case several repeat-structure components make up the material, preferably the
specimen thickness should be selected to at least 10 times the repeat-structure length scale in order to
reduce measurement errors and improve stability in the estimated results.
6.2.2 The specimen geometry is adapted to the geometry of the probe heating area. The cross-section
of the specimen shall completely embed the probe cross-section, and with a margin on each edge that
exceeds the specimen thickness on the sides of the probe, i.e. the cross-section of the specimen in
one direction shall be at least equal to the cross-section of the probe in the same direction plus 2 x
specimen thickness. For example, a probe of 30 mm × 30 mm cross section, and a specimen thickness of
5 mm, requires a specimen cross-section of a minimum 40 mm × 40 mm cross section. Note that in case
a specific probing depth is required to achieve, for instance if according to 6.2.1 a specific thickness
is required to reach at least 10 times the repeat-structure length scale in the thickness direction, the
cross-section of the specimen geometry as well as the geometry of the probe might need to be selected
differently: According to 6.2.3, the minimum cross-section distance across the probe area should be
selected at least 10 times the specimen thickness (assuming near-isotropic specimen conditions), or at
least 30 times the specimen thickness (in case anisotropy may be at hand) – which with the additional
requirement of a margin at each edge results in a different minimum specimen cross-section area.
6.2.3 Probes can be designed to be in different shapes, such as cylindrical, square or rectangular.
However, it should be noted that specimen thickness probed in the experiment will not exceed 1/10 of
the minimum distance across the cross-section of an effusivity probe, and hence the specimen thickness
can be adapted accordingly following the cross-section design of the probe.
6.2.4 In the basic setup, two specimen halves with symmetric setup facing the probe are assumed. A
flat surface (see 6.3.2) on each of the two specimen halves facing the probe is required.
6.2.5 In case in-plane thermal conductivity is estimated to be more than ten times the through-plane
thermal conductivity, the setup in 6.2 should not be used.
6.3 Specimen preparation
NOTE These specimen preparations apply to the setups described in 6.1 or 6.2.
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ISO/FDIS 22007-7:2023(E)
6.3.1 The specimen should be conditioned in accordance with the standard specification which
applies to the type of material and its particular use.
6.3.2 The specimen surfaces which are in contact with the probe should be plane and smooth. The
specimen halves shall be clamped on to both sides of the effusivity probe.
6.3.3 It is important to consider specimen materials prone to significant dimensional changes –
whether caused by measurements over large temperature ranges, thermal expansion, change of state,
phase transition, or other causes.
6.3.4 Care should be taken to ensure that the applied load does not affect the properties of the
specimen. For instance, for soft specimens tested according to setup 6.2, the clamping pressure should
not compress the specimen and thus change its thermal transport properties.
6.3.5 Heat sink contact paste shall not be used 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.
7 Procedure
7.1 The procedure for performing measurements shall be in accordance with ISO 22007-2, with the
following additional considerations.
7.2 As described in Clause 6, the preparation of specimen is connected directly with the selection of
effusivity probe to be used.
7.3 For rod shaped specimens, it is important to ensure that heat losses to the surroundings can
1/2 -2 -1
be controlled to a minimum. For specimens of thermal effusivity more than 1 000 W⋅s ⋅m ⋅K it is
normally enough with air, vacuum, or styrofoam insulation applied on the lateral surfaces.
7.4 For rod shaped specimens, it is important to ensure a correct measurement time. This is obtained
by ensuring that the probing depth is at least 1/3 of the rod length, but not exceeding the rod length.
A couple of scouting measurement may sometimes be made, in order to find a suitable measurement
time. In case there are repeat components making up the length of the rod, the probing depth into the
specimen shall be at least 10 times the characteristic length of the components making up the material
or of any inhomogeneity in the material, in the direction of the rod axis.
The expression for the normal-direction probing depth is given by Formula (1):
Δpt=2 α (1)
prob n max
where
t
is the maximum time of the time window used for calculating the thermal-transport proper-
max
ties;
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ISO/FDIS 22007-7:2023(E)
α
is the thermal diffusivity of the specimen material in the normal direction to the probe sur-
n
face.
In case the thermal diffusivity α is not known, the volumetric specific heat capacity of the specimen
n
should be estimated, either from tabulated data or by direct – separate – measurement by an alternative
method, in order to compute the probing depth according to Formula (2):
−1
12/
Δpb=2 tcρ (2)
() ()
prob npmax
7.5 For rod-shaped specimens, the heat pulse power and test time should use Table 1 or a scouting
experiment, as a guideline.
7.6 For rod-shaped specimens, in case the specimen can be considered being anisotropic, and the
timescale for heat to spread across the rod cross-section is considered to be much smaller than the total
experimental test time, the effects of anisotropy can be assumed to not influence the estimation of the
normal-direction thermal effusivity. For an anisotropic homogeneous specimen, where equal heating
can be assumed across the probe position cross-section, the conditions of the 1-dimensional setup can
also be assumed.
7.7 For rod-shaped specimens, the heat losses from lateral surfaces influence the accuracy of the
measurement. Estimated net heat losses at lateral surfaces (if these can be estimated) divided by total
heating power input in the probe, indicate the contribution of the lateral heat losses to the absolute
error of the measurement.
NOTE When making a measurement on a material with a high thermal effusivity, the temperature undergoes
[11]
a rapid increase at the very beginning of the transient followed by a much more gradual increase . The
insulating layer, between which the sensing spiral is sandwiched, causes this rapid increase. It has been shown
both experimentally and in computer simulations that the temperature difference across the insulating layer
becomes constant within a very short time and remains constant throughout the measurement. The reason is
that the total power output, the area of the sensing material and the thickness of the insulating layer are constant
during the test.
7.8 For specimens with a probe totally embedded in the specimen having a thermal effusivity
1/2 -2 -1
below 1 000 W·s ·m ·K , it is important to ensure a correct measurement time. This is obtained
by ensuring that the probing depth is at least 1/3 of the specimen thickness, but not exceeding the
specimen thickness. A couple of scouting measurement may sometimes be made, in order to find a
suitable measurement time. In case there are repeat components making up the thickness, the probing
depth into the specimen shall be at least 10 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. Formulas (1) and (2) can be used to compute the normal-direction probing
depth.
7.9 For specimens with a probe totally embedded in the specimen having a thermal effusivity below
1/2 -2 -1
1 000 W·s ·m ·K , the heat pulse power and test time should use Table 2 or a scouting experiment, as
a guideline.
7.10 For specimens with a probe totally embedded in the specimen having a thermal effusivity below
1/2 -2 -1
1 000 W·s ·m ·K , in case the in-plane thermal conductivity is higher than the through-plane thermal
conductivity, up to 10 times higher than the through-plane thermal conductivity, the normal-direction
probing depth should be controlled to within less than 1/30 of the smallest cross-section width of the
effusivity probe.
7.11 For specimens with a probe totally embedded in the specimen having a thermal effusivity below
1/2 -2 -1
1 000 W·s ·m ·K , the deviation between the experimental temperature response and that predicted
by the 1-dimensional model is increasing with experimental test time – due to side-ways heatflow at
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ISO/FDIS 22007-7:2023(E)
the edge of the effusivity probe. Following outlined procedures, this error can be controlled to within
the specified errors.
7.12 The thermal effusivity shall be reported along with the conditions under which it was measured,
such as temperature and pressure. The cardinal directions of the material and their orientations in
relation to the plane surface of the specimen shall be reported whenever a material is anisotropic.
Table 1 — Summary of recommended experimental parameters for a range of polymer
composites with different therma
...