ISO 3384:1991
(Main)Rubber, vulcanized or thermoplastic — Determination of stress relaxation in compression at ambient and at elevated temperatures
Rubber, vulcanized or thermoplastic — Determination of stress relaxation in compression at ambient and at elevated temperatures
Caoutchouc vulcanisé ou thermoplastique — Détermination de la relaxation de contrainte en compression à température ambiante et aux températures élevées
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INTERNATIONAL
STANDARD
3384
Third edition
1991-12-01
Rubber, vulcanized or thermoplastic -
Determination of stress relaxation in
compression at ambient and at elevated
temperatures
Caontchouc vnlcanis6 ou thermoplastique - Determination de la
relaxation de contrainte en compression 3 temperature ambiante et aux
tempk-atures elevees
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Reference number
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ISO 3384:1991(E)
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ISO 3384:1991(E)
Foreword
ISO (the International Organization for Standardization) is a wer-llfwide
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
International organizations, govern-
represented on that committee.
mental and non-governmental, in Liaison with ISO, also take part in the
work. ISO collaborates closely with the International Electr-otechnical
Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the mernber bodies for voting. Publication as an lnter-
national Standard requires approval by at least 75 % of the member
bodies casting a vote.
\
International Standard ISO 3384 was prepared by Technical Committee
ISO/TC 45, Rubber and rubber producfs, Sub-Committee SC 2, Physical
and degrada fion fests.
This third edition cancels and replaces the second edition
(ISO 3384:1986), of which it constitutes a technical revision.
0 ISO 1991
All rights reserved. NO part of this publication may be reproduced or utilized in any fort71
or by any means, electronie or mechanical, including photocopying and micrcfil111, wi{/jqrlt
Permission in writing from the publisher.
nization for Standardization
international Orga
Case Postale 56 + CH-121 1 Geneve 20 * Switzerland
Printed in Switzer-land
ii
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ISO 3384:1991(E)
Introduction
When a constant strain is applied to rubber, the forte necessary to
maintain that strain is not constant but decreases with time; this be-
haviour is called “stress relaxation”. Conversely, when rubber is sub-
jected to a constant stress, an increase in the deformation takes place
with time; this behaviour is called “creep”.
The processes responsible for stress relaxation may be physical or
chemical in nature, and under all normal conditions both types of proc-
ess will occur simultaneously. However, at normal or low temperatures
and/or short times, stress relaxation is dominated by physical processes
whilst at high temperatures and/or long times Chemical processes at-e
dominant. Hence it is neither safe to extrapolate time/stress relaxation
curves in Order to predict stress relaxation after periods considerably
lonqer than those covered by the test, nor to use tests at higher tem-
peritures as accelerated tests to give information on stress relaxation
at lower temperatures.
In addition to the need to specify the temperatures and time intervals in
a stress relaxation test, it is also necessary to specify the initial stress
and the previous mechanical history of the test piece since these may
also influence the measured stress relaxation, particularly in rubbers
containing fillers.
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INTERNATIONAL STANDARD ISO 3384:1991 (E)
Rubber, vulcanized or thermoplastic - Retermination of
stress relaxation in compression at ambient and at elevated
temperatures
values and general rules for sp ecifying
1 Scope
requirements.
This International Standard specifies threc methods
ISO 471:1983, Rubber - Standard t erzjpera h-es, hu-
for determining the decrease in counterforce ex-
midities ar,d times for the conditionirig and testing
er-ted by a test piece of vulcanized or thermoplastic
of fest pieces.
rubber which has been compressed to a constant
deformation and maintained thus at a pre-
ISO 1817: 1985, Rubber-, vulcanized -- Determination
determined test temperature.
of the effec t of hquids.
Two forms of test piece arc permitted: cylindrical
ISO 1826:1981, Rubber, vulcanized - Time-intervaI
test. pieces and rings. Different shapes and sizes of
between vulcanization and tesfinq -- S~ecifkation.
test piece give different results, and comparison of
c
results shkuld be lirnited to test pieces of similar
ISO 3383:1985, Rubber - Genera/ directions for
size and shape.
achieving elevated or subnormai temperatures for
The use of rinq test pieces is particularly suitable fof
test purposes.
the determina’iion of str-ess relaxation in liquid envi-
ronments.
ISO 3601-1:1988, Fluid Systems - Sealing devices -
0-rinqs --- Part 1: Inside diameters, Cross-sec tions,
Testing at temperatures below Standard temper-
tolerantes and size identification Code.
ature is not specified.
ISO 4648:1991, Rubber, vulcanized or thermoplastic
The methods have been used for low-temperature
- Determination of dimensions of test pieces and
testinq, but their reliability under these conditions is
products for test purposes.
not pt’oven.
ISO 4661-1:1986, Rubber, vrrlcanized -- Preparation
of samples and test pieces -- Part 1: Physical tests.
2 Normative references
The followinq Standards contain provisions which,
3 Definition
through refe;ence in this text, constitute provisions
of this International Standard. At the tirne of publi-
For the purposes of this International Standard, the
cation, the editions indicated wer-e valid. All stan-
following definition applies.
dards are subject to revision, and Parties to
agreements based on this International Standard
3.1 compression stress relaxation: The reduction in
ar-e encouraged to investigate the possibility of ap-
compressive forte, expressed as a percentage of
plying the most recent editions of the Standards in-
the initial forte, which occurs with time after the
dicated below. Members of IEC and ISO maintain
application sf a constant compressive strain.
registers of currently valid International Standards.
ISO 37: 1977, Rubber, vuicanized --- Determination of 4 Principle
tensile stress-strah properfies.
A test piece of vulcanized or thermoplastic rubber
ISO 468: 1982, Surface rotrghness --- Parameters, their is compressed to a constant deformation and main-
1
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ISO 3384:1991 (E)
Speed and for rneasuring the counterforce exerted
tained at a pre-determined test temperature. The
by the compressed test piece with an accuracy of
decrease in counterforce that is exerted is then
measured. 1 % of the measured value.
In method A, the compression is applied and all The device shall be capable of setting and main-
counterforce measurements are made at the test taining the compression during the whole duration
temperature. of the test and it shall be possible to keep it in an
oven at the specified test temperature. Care shall
In method B, the compression is applied and all
be taken to ensure that there is no loss of heat from
counterforce measurements are made at Standard
the test piece, for example by conduction through
temperature. The test pieces are stored at the test
metal Parts which at-e connected with the outside of
temperature.
the oven.
In method C, the compression is applied at Standard
temperature and all counterforce measurements are
5.2 Counterforce-measuring device, capable of
made at the test temperature.
measuring compression forces in the desired range
with an accuracy of 1 % of the measured value. The
NOTE 1 The three methods A, B and C of carrying out
device may be one that monitors the test piece dur-
the measurement do not give the Same values of stress
ing the whole duration of test, in which case a con-
relaxation, and comparison of values obtained from the
tinuous measurement of the Change of counlerforce
three methods should be avoided. The method selected
with time is possible. The stiffness of the counter-
for use depends on the pur-pose of the test. Thus, for fun-
damental studies and in applications where sealing at el- forte measuring device shall be sufficient for the
evated temperatures is a Problem, method A or C may
Change in compression of the test piece due to the
be preferred, and in applications where temperature cy-
relaxation of the load to he less than 0,02 mm.
cling from normal to an elevated temperature is a prob-
lem, method B may he preferred.
Alternatively, a compression testing machine may
be used to measure the counterforce at prescribed
time intervals. In this case, the forte necessar-y to
5 Apparatus Cause a slight increase in the compression of the
Zest piece is measured. This additional compression
shall be as small as possible and in no case greater
5.1 Compression device, consisting of two parallel,
than a forte of 1 N for balance-type machines, or
flat, highly polished plates made frorn chromium-
greater than OJE nim for stress/strain-type rna-
plated or stainless steel or other corrosion-resistant
chines, applied in either case without overshoot.
material, between the faces of which the test pieces
are compressed.
5.3 Test chamber, cornplyinq with the requirements
\.
Flatne SS, sur ,face roughness, parallelism and rigidity
of ISO 3383.
of the plates are all important.
For tests in air, a well designed, uniformly heated
When the apparatus is disassembled, the com-
air oven shall be used, provided with adequate
Pression plates shall be flat to within 0,Ol mm. The
temperature control to maintain the specified air
finish of the surface shall not be worse than
temperatures within the tolerantes spccified in 8.2.
0,4 kirn Ra (See ISO 468). When the apparatus is as-
Satisfactory circulation of the air shall be secured
sembled without a specimen test piece, the gap be-
by means of a fan.
tween the plates shall not varv by more than
,
+ 0,Ol rnm.
-
For tests in Iiquids, the cornpression device shall be
totally immersed in the liquid in a bath, or a closed
When the test assembly is subjected to the test Ioad
vessel for volatile and toxic fluids, such that free
with a test piece between the plates, neither com-
circulation of the liquid tan take place through the
Pression plate shall bend by more than 0,Ol mm.
holes in the cornpression plates. The liquid shall be
maintained at the specified temperature by proper
The plates shall be of sufficient size to ensure that
contra1 of a heater and circulation of the liquid in the
the whole of the compressed test piece is within the
bath or, alternatively, by placing the liquid bath and
area of the plates.
compression device within an air oven as specified
above.
For ring test piec:es, the plates shall have holes of
at least 2 mm diameter drilled through their centre
portions to allow equalization of pressure and cir-
5.4 Temperature-measuring equipment, with a
culation of fluid inside the ring-shaped test piece.
sensing elemcnt, for- example a therrnocouple. The
It shall he possible to connect the compression de-
theI,nlo-rneasut.irlg element shall be mounted so that
vice to suitable equipment for compressing thc test it is locatcd no more than 2 mni ft-om a surface of
piece to the specified compression at the specified the test piece.
2
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ISO 3384:1991 (E)
6.2 Measurement af dimensions of test pieces
6 Test piece
The dimensions ofthe test pieces shali be measured
as specified in ISO 4648.
6.1 Type and preparation of test piece
6.3 Number of test pieces
6.1 .l General
At least two tests usinq separate test pieces shall
L
be carried out.
Test pieces may he prepared either by rnoulding or
in accordance with ISO 4661-1, by cutting from
moulded sheets or products.
6.4 Time interval between vulcanizatian and
testing
6.1.2 Cylindrical test pieces
The interval between vulcanization and testing shal!
be in accordance with ISO 1826.
The test piece shall be a cylindrical disc of diameter
13 mm -t 0,5 mm and thickness 6,3 mrn -t- 0,3 mm
- -
6.5 Canditianing af test pieces
or of diameter 29,0 mm & 0,5 mrn and thickness
12,5 mrn -5 0,5 mm. The smaller test piece is pre-
6.5.1 For many materials, and particularly for com-
ferred. ---
pounds containing substantial proportions of filter-,
rept-oducibility of results tnay be irnproved by me-
chanically conditioning the test piece followed by
6.1.3 Ring test pieces
thermal conditioning. This shall be carried out as
specified in 6.5.2. Alternatively, thermal conditioning
The preferred test piece is a ring of Square cross-
only shall be carried out as specified in 6.5.3.
section, tut from a flat sheet o
...
IS0
NORME
I NTE R NATIONALE 3384
Troisième édition
1991-12-01
Caoutchouc vulcanisé ou thermoplastique -
Détermination de la relaxation de contrainte en
compression a température ambiante et aux
températures élevées
Rubber, vulcanized or thermoplastic - Determination of stress
relaxation in compression at ambient and at elevated temperatures
Numéro de référence
____
--__ IS0 3384: 1991 (F)
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IS0 3384:1991 (F)
I nt roduct ion
Lorsqu’une déformation constante est appliquée sur du caoutchouc, la
force nécessaire pour la maintenir n’est pas constante, mais diminue
en fonction du temps; ce comportement est appelé <
contrainte),. Inversement, lorsqu’une contrainte constante est appliquée
sur du caoutchouc, la déformation augmente en fonction du temps; ce
com port em en t est appelé <
Les processus responsables de la relaxation de contrainte peuvent être
de nature physique ou chimique, et dans toutes les conditions normales
ces deux types de processus interviennent simultanément. Cependant,
aux températures normales ou basses et/ou pour des temps courts, la
relaxation de contrainte résulte principalement des processus physi-
ques, tandis qu’aux températures élevées et/ou pour des longues du-
rées, les processus chimiques sont les plus importants. En
conséquence, il faut se garder d’une part d’extrapoler les courbes de
relaxation de contrainte en fonction du temps dans le but de prédire la
relaxation de contrainte après des durées beaucoup plus longues que
celles de l’essai, d’autre part d’utiliser, en tant qu‘essais accélérés, des
essais à températures plus élevées pour obtenir des informations sur
la relaxation de contrainte à des températures plus basses.
Dans un essai de relaxation de contrainte, il faut non seulement préciser
les températures et les durées d’essai, mais aussi la déformation ini-
tiale et l’<
peuvent également influencer la relaxation de contrainte mesurée, no-
tamment dans le cas des caoutchouc chargés.
iii
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NORME INTERNATIONALE
IS0 3384:1991(F)
Caoutchouc vulcanisé ou thermoplastique - Détermination
de la relaxation de contrainte en compression à température
ambiante et aux températures élevées
IS0 37:1977, Caoutchouc vulcanisé - Essai de
1 Domaine d'application
traction-allongement.
La présente Norme internationale prescrit trois mé-
IS0 468:1982, Rugosité de surface - Paramètres,
thodes pour la détermination de la diminution de la
leurs valeurs et les règles générales de la détermi-
force de réaction exercée par une éprouvette de
nation des spécifications.
caoutchouc vulcanisé ou thermoplastique, compri-
mée sous déformation constante et maintenue dans
IS0 471 : 1983, Caoutchouc - Températures, humidi-
cet état à une température d'essai prédéterminée.
tés et durées normales pour le conditionnement et
l'essai des éprouvettes.
Deux types d'éprouvette peuvent être utilisés, des
éprouvettes cylindriques et des éprouvettes annu-
IS0 1817:1985, Caoutchouc vulcanisé - Détermi-
laires. Des éprouvettes de forme et de dimensions
nation de l'action des liquides.
différentes donnent des résultats différents, et seuls
les résultats obtenus avec des éprouvettes de forme
IS0 1826:1981, Caoutchouc vulcanisé - Délai 'entre
et de dimensions analogues peuvent être comparés.
vulcanisation et essai - Spécifications.
L'emploi d'éprouvettes annulaires convient particu-
IS0 3383:1985, Caoutchouc - Directives générales
lièrement pour la détermination de la relaxation de
contrainte en milieu liquide, pour l'obtention de températures élevées ou de
températures inférieures à la température normale
L'essai à des températures inférieures à la tempé-
lors des essais.
rature normale de laboratoire n'est pas spécifié.
IS0 3601-1:1988, Systèmes de fluides - Joints
Ces méthodes utilisées pour des essais à basse
d'étanchéité - Joints toriques - Partie I: Diamètres
température n'ont pas prouvé leur fiabilité.
intérieurs, sections, tolérances et code d'identifica-
tion dimensionnelle.
IS0 4648:1991, Caoutchouc vulcanisé ou thermo-
plastique - Détermination des dimensions des
éprouvettes et des produits en vue des essais.
2 Références normatives
IS0 4661-1:1986, Caoutchouc vulcanisé - Prépa-
Les normes suivantes contiennent des dispositions
ration des échantillons et éprouvettes - Partie I:
qui, par suite de la référence qui en est faite,
Essais physiques.
constituent des dispositions valables pour la pré-
sente Norme internationale. Au moment de la pu-
blication, les éditions indiquées étaient en vigueur.
3 Définition
Toute norme est sujette à révision et les parties
prenantes des accords fondés sur la présente
Pour les besoins de la présente Norme internatio-
Norme internationale sont invitées à rechercher la
nale, la définition suivante s'applique.
possibilité d'appliquer les éditions les plus récentes
des normes indiquées ci-après. Les membres de la
CE1 et de I'ISO possèdent le registre des Normes
3.1 relaxation de contrainte en compression: Dimi-
internationales en vigueur à un moment donné.
nution de la force de compression, exprimée en
1
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IS0 33841 991 (F)
- diamètre intérieur: 15,O mm f 0,2 mm
Pour les essais dans les liquides, le dispositif de
compression doit être totalement immergé dans un
bain du liquide, ou placé dans un récipient fermé - largeur radiale: 2,O mm k 0,2 mm
dans le cas de liquides volatils et toxiques et de fa-
Les feuilles peuvent être préparées par moulage ou
con que le liquide puisse circuler librement par les
à partir de produits finis par découpage et ponqage.
trous percés dans les plaques de compression. Le
liquide doit être maintenu à la température prescrite
En variante, un joint torique de code dimensionnel
au moyen d’une résistance chauffante régulée et
B0140G selon l’lS0 3601-1 (diamètre de la section
par circulation du liquide dans le bain ou bien en
droite 2,65 mm et diamètre intérieur 14,O mm) peut
variante en placant le bain de liquide et le dispositif
être utilisé comme éprouvette normalisée.
de compression dans une étuve à air telle que spé-
cifiée ci-dessus.
Des joints toriques d’autres dimensions, ainsi que
des joints d’étanchéité et des garnitures d’autres
5.4 Appareil de mesure de la température, avec un formes, peuvent être utilisées comme éprouvettes
élément capteur, par exemple un thermocouple. Cet non normalisées.
élément thermosensible doit être monté de manière
La plupart des appareils d‘essai ont des gabarits
à ne pas être à plus de 2 mm de la surface en
dans lesquels l’éprouvette est comprimée en vis-
contact avec l’éprouvette.
sant une plaque d
...
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