EN 60216-8:2013

Electrical insulating materials - Thermal endurance properties - Part 8: Instructions for calculating thermal endurance characteristics using simplified procedures

IEC 60216-8:2013 specifies the general ageing conditions and simplified procedures to be used for deriving thermal endurance characteristics, which are shown by temperature index (TI) and/or relative temperature index (RTI) and the halving interval (HIC). The procedures specify the principles for evaluating the thermal endurance properties of materials exposed to elevated temperature for long periods. In the application of this standard, it is assumed that a practically linear relationship exists between the logarithm of the time required to cause the predetermined property change and the reciprocal of the corresponding absolute temperature (Arrhenius relationship). For the valid application of the standard, no transition, in particular no first-order transition should occur in the temperature range under study.

Elektroisolierstoffe - Eigenschaften hinsichtlich des thermischen Langzeitverhaltens - Teil 8: Anweisungen zur Berechnung von charakteristischen Werten zum thermischen Langzeitverhalten unter Verwendung vereinfachter Verfahren

Matériaux isolants électriques - Propriétés d'endurance thermique - Partie 8: Instructions pour le calcul des caractéristiques d'endurance thermique en utilisant des procédures simplifiées

La CEI 60216-8:2013 spécifie les conditions de vieillissement générales et les procédures simplifiées à utiliser pour déduire les caractéristiques d'endurance thermique, qui sont représentées par l'indice de température (IT) et/ou l'indice de température relatif (RTI) et l'intervalle de division par deux (IDC). Les procédures spécifient les principes régissant l'évaluation des propriétés d'endurance thermique des matériaux exposés à une température élevée pendant de longues périodes. Dans le cadre de l'application de la présente norme, on considère qu'il existe une relation pratiquement linéaire entre le logarithme du temps nécessaire pour provoquer le changement de propriété prédéterminé et l'inverse de la température absolue correspondante (relation d'Arrhenius). Pour que l'application de la présente norme soit valide, il convient qu'aucune transition, en particulier aucune transition du premier ordre, ne se produise dans la plage de températures à l'étude.

Elektroizolacijski materiali - Lastnosti toplotne vzdržljivosti - 8. del: Navodila za izračunavanje karakteristik toplotne vzdržljivosti z uporabo poenostavljenih postopkov

Ta del standarda IEC 60216 določa splošne pogoje staranja in poenostavljene postopke, ki naj se uporabijo za izpeljavo lastnosti toplotne vzdržljivosti, ki so prikazane s toplotnim indeksom (TI) in/ali relativnim toplotnim indeksom (RTI) in razpolovnim intervalom (HIC). Postopki določajo načela za vrednotenje lastnostni toplotne vzdržljivosti materialov, ki so dolgo izpostavljeni povišani temperaturi. V uporabi tega standarda se predvideva, da obstaja praktično linearno razmerje med logaritmom časa, potrebnega za povzročitev spremembe vnaprej določene lastnosti, in recipročno glede na ustrezno absolutno temperaturo (Arrheniusovo razmerje). Za veljavno uporabo standarda se v proučevanem temperaturnem obsegu ne sme pojaviti prehod, zlasti pa ne prehod prvega reda. V ostalem delu tega standarda izraz »izolacijski materiali« vedno pomeni »izolacijski materiali in enostavne kombinacije takšnih materialov«.

General Information

• Status: Published
• Publication Date: 11-Jul-2013
• Withdrawal Date: 18-Apr-2016
• ICS: 17.220.99 - Other standards related to electricity and magnetism
• ICS: 29.035.01 - Insulating materials in general
• Technical Committee: CLC/SR 112 - Evaluation and qualification of electrical insulating materials and systems (to be defined)
• Drafting Committee: IEC/TC 112 - IEC_TC_112
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 12-Jul-2013
• Completion Date: 12-Jul-2013
• Ref Project: SIST EN 60216-8:2013 - Electrical insulating materials - Thermal endurance properties - Part 8: Instructions for calculating thermal endurance characteristics using simplified procedures

Relations

• Replaces: EN 60216-1:2001 - Electrical insulating materials - Properties of thermal endurance - Part 1: Ageing procedures and evaluation of test results
• Effective Date: 28-Jan-2023

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 60216-8:2013
01-september-2013
1DGRPHãþD
SIST EN 60216-1:2002

(OHNWURL]RODFLMVNLPDWHULDOL/DVWQRVWLWRSORWQHY]GUåOMLYRVWLGHO1DYRGLOD]D

L]UDþXQDYDQMHNDUDNWHULVWLNWRSORWQHY]GUåOMLYRVWL]XSRUDERSRHQRVWDYOMHQLK
SRVWRSNRY

Electrical insulating materials - Thermal endurance properties - Part 8: Instructions for

calculating thermal endurance characteristics using simplified procedures
Ta slovenski standard je istoveten z: EN 60216-8:2013
ICS:
29.035.01 Izolacijski materiali na Insulating materials in
splošno general
SIST EN 60216-8:2013 en

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

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SIST EN 60216-8:2013
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SIST EN 60216-8:2013
EUROPEAN STANDARD
EN 60216-8
NORME EUROPÉENNE
July 2013
EUROPÄISCHE NORM
ICS 17.220.99; 29.035.01 Supersedes EN 60216-1:2001 (partially)
English version
Electrical insulating materials -
Thermal endurance properties -
Part 8: Instructions for calculating thermal endurance characteristics
using simplified procedures
(IEC 60216-8:2013)
Matériaux isolants électriques - Elektroisolierstoffe -
Propriétés d'endurance thermique - Eigenschaften hinsichtlich des
Partie 8: Instructions pour le calcul des thermischen Langzeitverhaltens -
caractéristiques d'endurance thermique en Teil 8: Anweisungen zur Berechnung von
utilisant des procédures simplifiées charakteristischen Werten zum
(CEI 60216-8:2013) thermischen Langzeitverhalten unter
Verwendung vereinfachter Verfahren
(IEC 60216-8:2013)

This European Standard was approved by CENELEC on 2013-04-19. CENELEC 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 CENELEC 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 CENELEC member into its own language and notified

to the CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,

the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany,

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

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

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2013 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.

Ref. No. EN 60216-8:2013 E
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SIST EN 60216-8:2013
EN 60216-8:2013 - 2 -
Foreword

The text of document 112/236/FDIS, future edition 1 of IEC 60216-8, prepared by IEC/TC 112

"Evaluation and qualification of electrical insulating materials and systems" was submitted to the

IEC-CENELEC parallel vote and approved by CENELEC as EN 60216-8:2013.
The following dates are fixed:
(dop) 2014-01-19
• latest date by which the document has
to be implemented at national level by
publication of an identical national
standard or by endorsement
(dow) 2016-04-19
• latest date by which the national
standards conflicting with the
document have to be withdrawn
This document supersedes EN 60216-1:2001 (PART).

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

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

patent rights.
Endorsement notice

The text of the International Standard IEC 60216-8:2013 was approved by CENELEC as a European

Standard without any modification.

In the official version, for Bibliography, the following notes have to be added for the standards indicated:

IEC 60216-6 NOTE Harmonised as EN 60216-6.
IEC 60212 NOTE Harmonised as EN 60212.
ISO 2578:1993 NOTE Harmonised as EN ISO 2578:1998 (not modified).
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SIST EN 60216-8:2013
- 3 - EN 60216-8:2013
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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 edition cited applies. For undated

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

NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD

applies.
Publication Year Title EN/HD Year
IEC 60085 - Electrical insulation - Thermal evaluation EN 60085 -
and designation
IEC 60216-1 2013 Electrical insulating materials - Thermal EN 60216-1 2013
endurance properties -
Part 1: Ageing procedures and evaluation
of test results
IEC 60216-2 - Electrical insulating materials - Thermal EN 60216-2 -
endurance properties -
Part 2: Determination of thermal endurance
properties of electrical insulating materials -
Choice of test criteria
IEC 60216-3 - Electrical insulating materials - Thermal EN 60216-3 -
endurance properties -
Part 3: Instructions for calculating thermal
endurance characteristics
IEC 60216-4-1 - Electrical insulating materials - Thermal EN 60216-4-1 -
endurance properties -
Part 4-1: Ageing ovens - Single-chamber
ovens
IEC 60216-5 - Electrical insulating materials - Thermal EN 60216-5 -
endurance properties -
Part 5: Determination of relative thermal
endurance index (RTE) of an insulating
material
ISO 291 - Plastics - Standard atmospheres for EN ISO 291 -
conditioning and testing
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SIST EN 60216-8:2013
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SIST EN 60216-8:2013
IEC 60216-8
Edition 1.0 2013-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Electrical insulating materials – Thermal endurance properties –
Part 8: Instructions for calculating thermal endurance characteristics using
simplified procedures
Matériaux isolants électriques – Propriétés d'endurance thermique –
Partie 8: Instructions pour le calcul des caractéristiques d'endurance thermique
en utilisant des procédures simplifiées
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX R
ICS 17.220.99; 29.035.01 ISBN 978-2-83220-679-9

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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SIST EN 60216-8:2013
– 2 – 60216-8 © IEC:2013
CONTENTS

FOREWORD ........................................................................................................................... 3

INTRODUCTION ..................................................................................................................... 5

1 Scope ............................................................................................................................... 6

2 Normative references ....................................................................................................... 6

3 Terms, definitions, symbols and abbreviations .................................................................. 7

3.1 Terms and definitions .............................................................................................. 7

3.2 Symbols and abbreviations ...................................................................................... 8

4 Thermal endurance test procedure ................................................................................... 9

4.1 General ................................................................................................................... 9

4.2 Number of test specimens ....................................................................................... 9

4.3 Preparation of test specimens ............................................................................... 10

4.4 Preparation of ageing processes ........................................................................... 11

5 Simplified numerical and graphical evaluation procedures .............................................. 12

5.1 Outline description of procedures .......................................................................... 12

5.2 Simplified calculation procedures .......................................................................... 13

5.2.1 Validity of simplified calculations ............................................................... 13

5.2.2 Times to end-point ..................................................................................... 13

5.2.3 Calculation of the regression line ............................................................... 14

5.2.4 Calculation of deviation from linearity ........................................................ 15

5.2.5 Temperature index and halving interval ..................................................... 15

5.3 Data rescue ........................................................................................................... 16

5.4 Determination of RTI ............................................................................................. 16

5.5 Test report ............................................................................................................ 18

Bibliography .......................................................................................................................... 19

Figure 1 – Determination of the time to reach the end-point at each temperature –

Property variation (according to IEC 60216-1) ....................................................................... 14

Figure 2 – Thermal endurance graph – Temperature index – Halving interval ....................... 16

Figure 3 – Thermal endurance graph – Relative temperature index ....................................... 17

Table 1 – Suggested exposure temperatures and times for TI corresponding to

20 000 h ............................................................................................................................... 12

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SIST EN 60216-8:2013
60216-8 © IEC:2013 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ELECTRICAL INSULATING MATERIALS –
THERMAL ENDURANCE PROPERTIES –
Part 8: Instructions for calculating thermal endurance
characteristics using simplified procedures
FOREWORD

1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising

all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

international co-operation on all questions concerning standardization in the electrical and electronic fields. To

this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,

Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC

Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested

in the subject dealt with may participate in this preparatory work. International, governmental and non-

governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely

with the International Organization for Standardization (ISO) in accordance with conditions determined by

agreement between the two organizations.

2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international

consensus of opinion on the relevant subjects since each technical committee has representation from all

interested IEC National Committees.

3) IEC Publications have the form of recommendations for international use and are accepted by IEC National

Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC

Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any

misinterpretation by any end user.

4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications

transparently to the maximum extent possible in their national and regional publications. Any divergence

between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in

the latter.

5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity

assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any

services carried out by independent certification bodies.

6) All users should ensure that they have the latest edition of this publication.

7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and

members of its technical committees and IEC National Committees for any personal injury, property damage or

other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and

expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC

Publications.

8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of

patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60216-8 has been prepared by IEC technical committee 112:

Evaluation and qualification of electrical insulating materials and systems.
The text of this standard is based on the following documents:
FDIS Report on voting
112/236/FDIS 112/244/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

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SIST EN 60216-8:2013
– 4 – 60216-8 © IEC:2013

A list of all parts in the IEC 60216 series, published under the general title Electrical insulating

materials – Thermal endurance properties, can be found on the IEC website.

The committee has decided that the contents of this publication will remain unchanged until

the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data

related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
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SIST EN 60216-8:2013
60216-8 © IEC:2013 – 5 –
INTRODUCTION

The designation 'thermal endurance' is used here to refer to the test of thermal stress in air,

excluding any other influence or stress applied to the test specimens. Thermal endurance

properties evaluated in different environments and/or with different stresses applied to the

test specimens require different test procedures.

In this part of IEC 60216, the study of the thermal ageing of materials is based solely on the

change in certain properties resulting from a period of exposure to elevated temperature. The

properties studied are always measured after the temperature has returned to ambient.

Properties of materials change at various rates on thermal ageing. To enable comparisons to

be made of the thermal ageing of different materials, the criteria for judgment depend on the

type of property to be studied and its acceptable limiting value.
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SIST EN 60216-8:2013
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ELECTRICAL INSULATING MATERIALS –
THERMAL ENDURANCE PROPERTIES –
Part 8: Instructions for calculating thermal endurance
characteristics using simplified procedures
1 Scope

This part of IEC 60216 specifies the general ageing conditions and simplified procedures to

be used for deriving thermal endurance characteristics, which are shown by temperature

index (TI) and/or relative temperature index (RTI) and the halving interval (HIC).

The procedures specify the principles for evaluating the thermal endurance properties of

materials exposed to elevated temperature for long periods.

In the application of this standard, it is assumed that a practically linear relationship exists

between the logarithm of the time required to cause the predetermined property change and

the reciprocal of the corresponding absolute temperature (Arrhenius relationship).

For the valid application of the standard, no transition, in particular no first-order transition

should occur in the temperature range under study.

Throughout the rest of this standard the designation "insulating materials" is always taken to

mean "insulating materials and simple combinations of such materials".
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 edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60085, Electrical insulation – Thermal evaluation and designation

IEC 60216-1:2013, Electrical insulating materials –Thermal endurance properties – Part 1:

Ageing procedures and evaluation of test results

IEC 60216-2, Electrical insulating materials - Thermal endurance properties - Part 2:

Determination of thermal endurance properties of electrical insulating materials - Choice of

test criteria

IEC 60216-3, Electrical insulating materials – Thermal endurance properties – Part 3:

Instructions for calculating thermal endurance characteristics

IEC 60216-4-1, Electrical insulating materials – Thermal endurance properties – Part 4-1:

Ageing ovens – Single-chamber ovens
—————————
A sixth edition is due to be published shortly.
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SIST EN 60216-8:2013
60216-8 © IEC:2013 – 7 –

IEC 60216-5, Electrical insulating materials – Thermal endurance properties – Part 5:

Determination of relative thermal endurance index (RTE) of an insulating material

ISO 291, Plastics – Standard atmospheres for conditioning and testing
3 Terms, definitions, symbols and abbreviations

For the purposes of this document, the following terms, definitions, symbols and abbreviations

apply.
3.1 Terms and definitions
3.1.1
temperature index

numerical value of the temperature in degrees Celsius derived from the thermal endurance

relationship at a time of 20 000 h (or other specified time)
3.1.2
halving interval
HIC

numerical value of the temperature interval in Kelvin which expresses the halving of the time

to end-point taken at the temperature equal to TI

[SOURCE: IEC 60050-212:2010 [1] , definition 212-12-13, modified – omission of reference to

"relative temperature index”]
3.1.3
thermal endurance graph

graph in which the logarithm of the time to reach a specified end-point in a thermal endurance

test is plotted against the reciprocal thermodynamic test temperature
[SOURCE: IEC 60050-212:2010, definition 212-12-10]
3.1.4
thermal endurance graph paper

graph paper having a logarithmic time scale as the ordinate, graduated in powers of ten

(from 10 h to 100 000 h is often a convenient range) and values of the abscissa are

proportional to the reciprocal of the thermodynamic (absolute) temperature

Note 1 to entry: The abscissa is usually graduated in a non-linear (Celsius) temperature scale oriented with

temperature increasing from left to right.
3.1.5
degrees of freedom
number of data values minus the number of parameter values
3.1.6
end-point

limit for a diagnostic property value based on which the thermal endurance is evaluated.

—————————
Figures in square brackets refer to the Bibliography.
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SIST EN 60216-8:2013
– 8 – 60216-8 © IEC:2013
3.1.7
time to end-point
failure time
time to reach the end point or conventional failure
3.1.8
square of the correlation coefficient

fraction of the variation in one variable that may be explained by the other variable

Note 1 to entry: r is a square of correlation coefficient which explains the ratio of all data deviation on the

regression line.
3.1.9
destructive test

diagnostic property test, where the test specimen is irreversibly changed by the property

measurement, in a way which precludes a repeated measurement on the same specimen

3.1.10
non-destructive test

diagnostic property test, where the properties of the test specimen are not permanently

changed by the measurement, so that a further measurement on the same specimen may be

made after appropriate treatment
3.1.11
proof test

diagnostic property test, where each test specimen is, at the end of each ageing cycle,

subjected to a specified stress, further ageing cycles being conducted until the specimen fails

on testing
3.1.12
temperature group
temperature group of specimens

number of specimens being exposed together to the same temperature ageing in the same

oven

Note 1 to entry: Where there is no risk of ambiguity, either temperature groups or test groups may be referred to

simply as groups.
3.1.13
test group
test group of specimens

number of specimens removed together from a temperature group (as above) for destructive

testing
3.1.14
relative temperature index
RTI

numerical value of the temperature in degrees Celsius at which the estimated time to endpoint

of the candidate material is the same as the estimated time to endpoint of the reference

material at a temperature equal to its assessed temperature index
3.2 Symbols and abbreviations
a,b
Regression coefficients
Numbers of specimens for destructive tests
a,b,c,d
n Number of y-values
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SIST EN 60216-8:2013
60216-8 © IEC:2013 – 9 –
Total number of test specimens
Correlation coefficient
Fisher distributed stochastic variable
Reciprocal thermodynamic temperature (1/Θ)
Logarithm of time to end-point
Temperature, °C
Temperature, thermodynamic (Kelvin)
Value in Kelvin of 0 °C (273,15 K)
Time (to end-point)
TI Temperature index
HIC Halving interval at temperature equal to TI
RTI Relative temperature index
4 Thermal endurance test procedure
4.1 General

Simplified procedures, which do not test the data dispersion but only deviations from linear

behaviour, are described.

It is possible, with some limitations, to evaluate the thermal endurance data graphically. In

this case, statistical assessment of data dispersion is not possible, but it is considered

important to evaluate any deviation of the data from the linear relationship.

Since the temperature is very often the dominant ageing factor affecting an electrical

insulating material (EIM) certain basic thermal classes are useful and have been recognized

as such internationally (see IEC 60085).
4.2 Number of test specimens

The accuracy of endurance test results depends largely on the number of specimens aged at

each temperature. Generally, the following instructions, which influence the testing procedure,

apply.

a) For a criterion requiring non-destructive testing, in most cases a group of five test

specimens for each exposure temperature is adequate.

Where the test criterion for non-destructive or proof tests is based upon the initial value of

the property, this should be determined from a group of specimens of at least twice the

number of specimens in each temperature group

b) For proof-test criteria, a group of at least 11 and possibly 21 specimens will be required

for each exposure temperature.

The dimensions and method of preparation of the test specimens shall be in accordance

with the specifications given for the relevant test method.

c) For a criterion requiring a destructive test, the minimum total number (N) of test specimens

needed is derived as follows:
N = n × n × n + n (1)
a b c d
where
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SIST EN 60216-8:2013
– 10 – 60216-8 © IEC:2013

n is the number of specimens in a test group undergoing identical treatment at one

temperature and one treatment time and discarded after determination of the property

(usually five);
n is the number of treatments, i.e. exposure lengths, at one temperature;
n is the number of exposure temperature levels;

n is the number of specimens in the group used to establish the initial value of the

property. Normal practice is to select n = 2n when the diagnostic criterion is a
d a

percentage change of the property from its initial level. When the criterion is an absolute

property level, n is usually given the value of zero, unless reporting of the initial value

is required.

NOTE When there is a large number of specimens to be tested, it may be possible in certain cases to deviate

from the relevant test specifications and to reduce this number. However, it should be recognized that the precision

of the test result depends to a large extent on the number of specimens tested. In contrast, when the individual

results are too scattered, an increase in the number of specimens may be necessary in order to obtain satisfactory

precision. It is advisable to make an approximate assessment, by means of preliminary tests, of the number and

duration of the ageing tests required.
4.3 Preparation of test specimens

The specimens used for the ageing test should constitute a random sample from the

population investigated and are to be treated uniformly.

The material specifications or the test standards will contain all necessary instructions for the

preparation of specimens.

The thickness of specimens is in some cases specified in the list of property measurements

for the determination of thermal endurance (see IEC 60216-2); otherwise the thickness shall

be reported. Some physical properties are sensitive even to minor variations of specimen

thickness. In such cases, the thickness after each ageing period may need to be determined

and reported if required in the relevant specification.

The thickness is also important because the rate of ageing may vary with thickness. Ageing

data of materials with different thicknesses are not always comparable. Consequently, a

material may be assigned more than one thermal endurance characteristic derived from the

measurement of properties at different thicknesses.

The tolerances of specimen dimensions should be the same as those normally used for

general testing; where specimen dimensions need smaller tolerances than those normally

used, these special tolerances should be given. Screening measurements ensure that

specimens are of uniform quality and typical of the material to be tested.

Since processing conditions may significantly affect the ageing characteristics of some

materials, it shall be ensured that, for example, sampling, cutting sheet from the supply roll,

cutting of anisotropic material in a given direction, moulding, curing, pre-conditioning, are

performed in the same manner for all specimens.

It is good practice to keep an adequate number of test specimens separately as a reserve of the

original material batch from which such specimens may subsequently be prepared. In this

way, any required ageing of additional specimens in case of unforeseen complications will

introduce a minimum risk of producing systematic differences between groups of specimens.

Such complications may arise, for example, if the thermal endurance relationship turns out to

be non-linear, or if specimens are lost due to thermal runaway of an oven. Moreover they can

be used:

– for cases in which the accuracy requires heat ageing at an additional temperature;

– as reference specimens.
They shall be stored in an appropriately controlled atmosphere (see ISO 291).
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SIST EN 60216-8:2013
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Thermosetting materials shall be conditioned for 48 h at the lowest exposure temperature of

the range selected.

If necessary, thermoplastic materials should be annealed for 48 h at the lowest exposure

temperature of the range selected.
4.4 Preparation of ageing processes – exposure temperature and cycle time

For TI determinations, test specimens should be exposed to not less than three, preferabl

...