ISO 2557-1:1976
(Main)Plastics — Amorphous thermoplastic moulding materials — Preparation of test specimens with a defined level of shrinkage — Part 1: Test specimens in the form of parallelepipedic bars (Injection moulding and compression moulding)
Plastics — Amorphous thermoplastic moulding materials — Preparation of test specimens with a defined level of shrinkage — Part 1: Test specimens in the form of parallelepipedic bars (Injection moulding and compression moulding)
Plastiques — Matières à mouler thermoplastiques amorphes — Préparation d'éprouvettes à niveau défini de retrait — Partie 1: Éprouvettes sous forme de barreaux parallélépipédiques (Moulage par injection et moulage par compression)
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INTERNATIONAL STANDARD 2557
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INTERNATIONAL ORGA51ZATION FOR STANDARDIZATION .MEA\AL ti41’01H4R OPr4HM3AUMR fl0 CTAHilAPTM3AUMM .ORGANIS4TION INTERNATIONALE DE NORMALISATION
Plastics - Amorphous thermoplastic moulding materials -
Preparation of test specimens with a defined level of shrinkage
Matières plastiques - Matières à mouler thermoplastiques amorphes - Preparation d’éprouvettes
à niveau défini de retrai?
First edition - 1976-04-15
L
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- Lu UDC 678.5 : 678.7 : 620.11 Ref. No. IS0 2557-1976 (E)
rn p.
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Descriptors : plastics, thermoplastic resins, moulding materials, test specimens.
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Price based on 5 pages
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FOREWORD
IS0 (the International Organization for Standardization) is a worldwide federation
of national standards institutes (IS0 Member Bodies). The work of developing
International Standards is carried out through IS0 Technical Committees. Every
Member Body interested in a subject for which a Technical Committee has been set
up 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.
Draft International Standards adopted by the Technical Committees are circulated
to the Member Bodies for approval before their acceptance as International
Standards by the IS0 Council.
International Standard IS0 2557 was drawn up by Technical Committee
ISO/TC 61, Plastics, and circulated to the Member Bodies in July 1973.
It has been approved by the Member Bodies of the following countries :
Australia Hungary South Africa, Rep. of
Austria Israel Sweden
Belgium Italy Thailand
Japan United Kingdom
Bulgaria
Netherlands U.S.A.
Czechoslovakia
New Zealand Yugoslavia
Egypt, Arab Rep. of
France Poland
Germany Romania
No Member Body expressed disapproval of the document.
O International Organization for Standardization, 1976
Printed in Switzerland
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INTERNATIONAL STANDARD IS0 2557-1976 (E)/ERRATUM
Published 1980-1 1-15
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION *MEXnYHAPOnHAR OPrAHMJAUMR fl0 CTAHnAPTM3AUHH -ORGANISATION INTERNATIONALE DE NORMALISATION
[New title :]
Plastics - Amorphous thermoplastic moulding materials - Preparation of test specimens with a defined
level of shrinkage - Part 1 : Test specimens in the form of parallelepipedic bars (Injection moulding and
compression moulding)
Plastiques - Matières à mouler thermoplastiques amorphes - Préparation d'éprouvettes à niveau défini de retrait - Partie 1 :
Eprouvettes sous forme de barreaux parallélépipédiques (Moulage par injection et moulage par compression)
e, ERRATUM
Cover page and page 1
Amend the title as shown above.
All pages
Replace the reference number "2557" by "255711 ".
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INTERNATIONAL STAN DARD IS0 2557-1976 (E)
Plastics - Amorphous thermoplastic moulding materials -
Preparation of test specimens with a defined level of shrinkage
O INTRODUCTION
2.2 defined state (of specimens) : The state in which the
specimens have a defined level of shrinkage which is either
The properties of test specimens of thermoplastic materials
specified for the material under consideration or established
are influenced by their molecular Orientation. The degree
by agreement.
and direction of such orientation are dependent upon the
methods used to prepare the specimens. The amount of
orientation induced during processing can be assessed by
c.
2.3 basic state (of specimens) : The state in which the
measuring the shrinkage of the specimens at an elevated
specimens are considered to be if they do not shrink more
temperature. Reproducible test results can best be obtained
than 2 % in length when tested as specified in 4.3 and if,
by using test specimenps which are in the same state of
after that treatment, they are not changed significantly
orientation. For industrial purposes, the conditions of
either in appearance or in mechanical properties.
similar state are reasonably fulfilled when the measured
shrinkages of test specimens produced by a specified heat
treatment are equal.
2.4 shrinkage : The percentage change in length measured
as defined in 4.2 when the specimen is subject to a specified
heat treatment.
1 SCOPE AND FIELD OF APPLICATION
This International Standard specifies procedures for the
preparation of test specimens with a defined level of Io -11
S%=- x 100
shrinkage which is measured by determining the
IO
longitudinal shrinkage of a sample of the specimens by a
standardized test method. The method is suitable only for
where
specimens exhibiting uniaxial orientation, i.e. specimens in
the form of bars and made from rigid amorphous
S is the shrinkage;
thermoplastics other than those containing fibre
reinforcements.
Io is the original length;
IL
By modifying the conditions of the moulding operation for
is the length after shrinkage;
Il
test specimens with a defined
the mould and machine used,
level of shrinkage and, consequently, in the same state of
molecular orientation can be prepared. Those conditions
2.4.1 maximum shrinkage (S,) : The shrinkage deter-
need to be determined for each type of moulding material.
mined at a relatively high temperature. Its value is not
Unless otherwise agreed, the choice between determining
influenced by small changes of time or temperature.
partial or maximum shrinkage shall be decided by the
material specification which shall also define the required
level of shrinkage and the conditions of its determination.
2.4.2 partial shrinkage 6,) : The shrinkage measured
under less extreme, but specified, conditions; for example
VST/B + 20 OC, 45 min.’)
2 DEFINITIONS
S, is influenced by the temperature and the time of
For the purposes of this International Standard, the
treatment (S, < S, 1.
following definitions apply :
2.1 state (of a specimen) : The condition of a specimen as
NOTE - The temperature used for the heat treatment should be
characterized by its shrinkage.
above the glass transition temperature of the material.
For convenience, the temperature chosen may be related to the Vicat softening temperature, method B (VST/B, see IS0 306, Plastics -
1 )
Determination of the Vicat softening temperature of thermoplastics).
1
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6
IS0 2557-1976 (E)
3 PREPARATION OF TEST SPECIMENS resultant specimens determined in accordance with 4.2 are
then plotted versus cylinder temperatures as shown in
figure3 and a curve is drawn. Subsequently, when the
3.1 Apparatus
same kind of material is to be moulded with that particular
3.1.1 Injection moulds
machine and mould, the cylinder temperature expected
to produce the desired level of shrinkage can be read off the
Single-cavity moulds are recommended. If multi-cavity
curve usually without need for additional experimentation.
moulds are used, the cavities must be similar and should be
fed in parallel and not in series. The sprues and runners
Alternatively, another processing variable such as injection
should be as short as possible and the gate located at one
speed (injection pressure) may be correlated with shrinkage,
end of the specimen. Gate diameters should be as large as
while maintaining other machine control settings constant.
possible and so selected that a balance of shrinkages
The injection speed required to produce a desired shrinkage
between specimens from all of the cavities may be attained.
value may then be estimated.
NOTE - Bending of specimens during shrinkage is due to an
asymmetric distribution of stresses and orientation. The difficulty
3.2.2 Compression-moulded specimens
be obviated by careful mould construction, in particular
can
balanced cooling.
The specimens shall be compression moulded direct to the
required shape or be machined from moulded sheet (see
3.1.2 Compression moulds
3.1.2). The time, temperature and pressure and the
quantity of the granules or plastic powder used shall
The mould assembly is illustrated in figures 1 and 2. It
conform to the directions given in the specification of the
consists of a multi-cavity mould, two metal plates, and
moulding material. If there are no recommendations, the
0,l mm foils made of soft ahminium. The mould shall be
amount of material shall be such that the mould cavity is
made of tool steel or stainless steel.
completely filled after moulding and a minimum of flash is
For the moulding of sheets, the assembly of the mould is
formed.
the same except that a "picture-frame" type of mould
NOTE - Pre-compaction by milling or extrusion may also be used.
is used instead of a multi-cavity mould.
NOTE - Foils are helpful for equalizing cooling and in dissipating
volatile material which c
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