EN ISO 2578:1998

SLOVENSKI STANDARD
01-maj-2000
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Plastics - Determination of time-temperature limits after prolonged exposure to heat (ISO
2578:1993)
Kunststoffe - Bestimmung der Temperatur-Zeit-Grenzen bei langanhaltender
Wärmeeinwirkung (ISO 2578:1993)
Plastiques - Détermination des limites temps-températures apres exposition a l'action
prolongée de la chaleur (ISO 2578:1993)
Ta slovenski standard je istoveten z: EN ISO 2578:1998
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL
ISO
STANDARD
Second edition
1993-08-01
Plastics
- Determination of
time-temperature limits after prolonged
exposure to heat
Plas tiques - Determination des limites temps-tempka tures apr&
exposition 2 I’action prolong6e de Ia chaleur
Reference number
ISO 2578: 1993(E)
ISO 2578:1993(E)
Contents
Page
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~.
2 Normative references . . . . . . . . .*.
3 Def initions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 Principle ’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 Choice of test .,.,.,,.
Choice of end-point . . . . . . . . .*. 3
,.,.,. 3
7 Test specimens
.,.,.,,,.,.~.,.,,,., 3
8 Exposure temperatures
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*. 3
9 Ageing ovens
10 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.,. . . . . . 4
11 Evaluation of results
................... 7
12 Determination of the relative temperature index
................... 8
13 Test report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Annexes
Calculation of the regression line .
A
............................................................ 13
B Correlation coefficient
............ 14
C Recommended test schedule for primaty properties
0 ISO 1993
All rights reserved. No part of this publication may be reproduced or utilized in any form or
by any means, electronie or mechanical, including photocopying and microfilm, without per-
mission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1 211 Geneve 20 l Switzerland
Printed in Switzerland
ii
ISO 2578:1993(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. Esch 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.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 2578 was prepared by Technical Committee
ISO/TC 61, Plasties, Sub-Committee SC 6, Ageing, chemica/ and environ-
mental resis tance.
This second edition cancels and replaces the first edition
(ISO 2578:1974), of which it constitutes a technical revision.
Annexes A and B form an integral part of this International Standard. An-
nex C is for information only.
. . .
Ill
ISO 2578:1993(E)
Introduction
During the preparation of this International Standard, account was taken
of the contents of IEC 216. Accordingly, the terms and definitions in this
International Standard, as well as the procedures described, are in line or
identical with those specified in IEC 216.

ISO 2578:1993(E)
INTERNATIONAL STANDARD
Plastics - Determination of time-temperature limits
after prolonged exposure to heat
cation, the editions indicated were valid. All Standards
1 Scope
are subject to revision, and Parties to agreements
based on this International Standard are encouraged
1.1 This International Standard specifies the princi-
to investigate the possibility of applying the most re-
ples and procedures for evaluating the thermal en-
cent editions of the Standards indicated below.
durante properties of plastics exposed to elevated
Members of IEC and ISO maintain registers of cur-
temperature for long periods.
rently valid International Standards.
1.2 The term thermal endurante is used here to re-
ISO 291: 1977, Plastics - Standard atmospheres for
fer to tests made in air, excluding any other influence
conditioning and testing.
or stress applied to the test specimens. Thermal en-
durante properties evaluated in different environ-
IEC 216-1 :1990, Guide for the determination of ther-
ments and/or with different Stresses applied to the
mal endurante properties of electrical insulating ma-
test specimens require different test procedures.
terials - Part 1: General guidelines for ageing
procedures and evaluation of test results.
1.3 In this International Standard, the study of the
thermal ageing of plastics is based solely on the I EC 216-2: 1990, Guide for the determination of ther-
mal endurante properties of electrical insulating ma-
Change in certain properties resulting from a period
Part 2: Choice of the test criteria.
terials -
of exposure to elevated temperature. The properties
studied are always measured after the temperature
I EC 216-3-1: 1990, Guide for the determination of
has returned to ambient.
thermal endurante properties of electrical insula ting
The various properties of plastics Change at various
ma terials - Part 3: Instructions for calculating thermal
rates on thermal ageing. To enable comparisons to be
endurante characteristics - Section 1: Calculations
made of the thermal ageing of different plastics, the
using mean values of normally distributed complete
criteria for judgement depend on the type of property
data.
to be studied and its acceptable limiting value.
IEC 216-3-3:-, ‘1 Guide for the determina tion of ther-
mal endurante properties of electrical insulating ma-
1.4 In the application of this Standard it is assumed
terials - Part 3: Instructions for calculating thermal
that a practically linear relationship exists between the
endurante characteristics - Section 3: Calculations
logarithm of the time required to Cause the predeter-
for incomple te da ta.
mined property Change and the reciprocal of the cor-
responding absolute temperature (Arrhenius Law).
IEC 216-4-1: 1990, Guide for the determination of
For the plastics tested, no transition, in particular a
thermal endurante properties of electrical insulating
first-Order transition, should occur in the temperature
- Part 4: Ageing ovens - Section 1:
ma terials
range under study.
Single-chamber ovens.
I EC 216-5: 1990, Guide for the determination of ther-
2 Normative references
mal endurante properties of electrical insulating ma-
terials - Part 5: Guidelines for the application of
The following Standards contain provisions which,
thermal endurante characteristics.
through reference in this text, constitute provisions
of this International Standard. At the time of publi-
1) To be published. [15B (BC.1 821

ISO 2578:1993(E)
a mechanical, Optical or electrical property) are deter-
3 Definitions
mined as a function of time.
For the purposes of this International Standard, the
The procedure is continued until the relevant thresh-
following definitions apply.
old value of that characteristic has been reached, re-
sulting in the time to failure at that particular
3.1 temperature index (Tl): Number corresponding
temperature.
to the temperature, in degrees Celsius, derived from
the thermal endurante relationship at a given time
Further specimens are exposed at at least two other
(normally 20 000 h).
temperatures and the variations in the relevant char-
acteristic determined. lt is recommended to heat-age
3.2 relative temperature index (RTI): Temperature
test specimens at three to four temperatures, and
index of a test material, obtained at the time which
determine the time to failure for each of the tem-
corresponds to the known temperature index of a
peratures.
reference material when both materials are subjected
to the same ageing and diagnostic procedures in a
comparative test.
4.2 Determination of Tl
3.3 halving interval (HIC): Number corresponding
The times to failure are plotted versus the reciproca
to the temperature interval, in degrees Celsius, which
values of the exposure temperatures. The intersectior
expresses the halving of the time to end-point taken
of this curve with the Chosen time limit (in genera
at the temperature of the Tl or the RTL
20 000 h) gives the temperature index sought.
HIC is a measure of the slope of the thermal endur-
ante graph. lt is not constant, but varies with tem-
perature even when the thermal endurante
4.3 Use of correlation coefficient
relationship is linear. In many practical cases, the error
arising from the use of HIC in the temperature range
The reliability of the extrapolation of. the graph de-
of interest remains within acceptable limits.
pends on obtaining an acceptable Arrhenius Plot,
which may not be possible with materials showing
3.4 thermal endurante graph (Arrhenius graph):
behaviour related to a transition phenomenon in the
Graph in which the Iogarithm of time to resch a
Chosen temperature range.
specified end-point in a thermal endurante test is
plotted versus the reciprocal thermodynamic (abso-
For this purpose the correlation coefficient r is calcu-
lute) test temperature.
lated in accordance with annex B. If this calculation
results in a value smaller than 0,95 (for three test
3.5 threshold value: Value, corresponding to a per-
temperatures; see also IEC 216), an additional test at
centage of the initial value of the property under in-
a different test temperature may improve the linearity
vestigation, at which the ageing test is stopped and
of data.
the time to failure is calculated.
NOTES
4.4 Determination of RTI
1 The level of 50 % is often used to determine the
threshold value.
For determination of RTI, the Chosen reference plas-
tic, its thermal endurante and the method of deter-
2 If a minimum value is required after ageing, it may be
mination are of central importante.
agreed between the interested Parties to use this minimum
value as the threshold value, instead of a percentage of the
The reference plastic shall be of the same type as the
initial value.
tested plastic, and have a history of satisfactory ser-
vice. lt shall have a known temperature index for the
3.6 test-specimen failure time: Time required at
property and a threshold value which are the Same,
the exposure temperature for a specimen to either fail
or at least reasonably similar to, those to be employed
the proof test or resch the threshold value of the
in the RTI test. The Tl and HIC of the reference ma-
characteristic under investigation, whichever is
terial should also be approximately the same as the
shorter.
values expected for the tested plastic.
Since processing conditions may significantly affect
4 Principle
the ageing characteristics of some materials, the
sampling, cutting of sheet from the supply roll, cutting
4.1 Determination of time to failure of anisotropic material in the same direction, mould-
ing, curing, preconditioning, etc. shall be performed in
At a Chosen temperature, the variations in the nu- the same manner for both materials, and the speci-
merical value of a Chosen characteristic (for example, mens shall be tested in the Same thickness.
ISO 2578:1993(E)
the relevant test specifications and to reduce this number.
5 Choice of test
However, it must be recognized that the precision of the
test result depends to a large extent on the number of
The test Chosen shall relate to a characteristic which
specimens tested.
is likely to be of significance in practice and, wherever
possible, use shall be made of test methods specified
5 In contrast, when the individual results are too scattered,
in International Standards. If the dimensions and/or
an increase in the number of specimens may be necessary
form of the test specimens are altered by the heat in Order to obtain satisfactory precision.
treatment, then only test methods which are inde-
6 lt is advisable to make an approximate assessment, by
pendent of these effects may be used.
means of preliminary tests, of the number and duration of
the ageing tests required.
6 Choice of end-point
8 Exposure temperatures
For the selection of the end-point, two factors shal
...