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INTERNATIONAL

STANDARD

ISO
37
Sixth edition
2017-11



Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties
Caoutchouc vulcanisé ou thermoplastique — Détermination des caractéristiques de contrainte-déformation en traction



Foreword

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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).
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This document was prepared by Technical Committee ISO/TC 45, Rubber and rubber products, Subcommittee SC 2, Testing and analysis.
This sixth edition cancels and replaces the fifth edition (ISO 37:2011), which has been technically revised.
The main changes compared to the previous edition are as follows:
the cutter angle range in Figure 3 has been changed to 30° - 35°;
dimension B of the dumb-bell test piece has been corrected in Figure 3;
accuracy requirement for force measurement has been changed to Class 1;
dimensions of ∅d1 and ∅d2 in Figure 5 and Table 3 have been corrected;
the test results of interlaboratory test programmes (ITP) have been added.
INTERNATIONAL STANDARD ISO 37:2017 (E)
Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties

1 Scope

This document specifies a method for the determination of the tensile stress-strain properties of vulcanized and thermoplastic rubbers.
The properties which can be determined are tensile strength, elongation at break, stress at a given elongation, elongation at a given stress, stress at yield and elongation at yield. The measurement of stress and strain at yield applies only to some thermoplastic rubbers and certain other compounds.

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 5893, Rubber and plastics test equipment — Tensile, flexural and compression types (constant rate of traverse) — Specification
ISO 23529:2016, Rubber — General procedures for preparing and conditioning test pieces for physical test methods

3 Terms and definitions

For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
IEC Electropedia: available at http://www.electropedia.org/
ISO Online browsing platform: available at http://www.iso.org/obp
3.1
tensile stress
S
stress applied so as to extend the test piece
Note 1 to entry: It is calculated as the applied force per unit area of the original cross-section of the test length.
3.2
elongation
E
tensile strain, expressed as a percentage of the test length, produced in the test piece by a tensile stress (3.1)
3.3
tensile strength
TS
maximum tensile stress (3.1) recorded in extending the test piece to breaking point
Note 1 to entry: See Figure 1.
3.4
tensile strength at break
TSb
tensile stress (3.1) recorded at the moment of rupture
Note 1 to entry: See Figure 1.
Note 2 to entry: The values of TS and TSb might be different if, after yield at Sy, the elongation (3.2) continues and is accompanied by a drop in stress, resulting in TSb being lower than TS [see Figure 1 c)].
3.5
elongation at break
Eb
tensile strain in the test length at breaking point
Note 1 to entry: See Figure 1.
3.6
elongation at a given stress
Es
tensile strain in the test length when the test piece is subjected to a given tensile stress (3.1)
3.7
stress at a given elongation
Se
tensile stress (3.1) in the test length required to produce a given elongation (3.2)
Note 1 to entry: In the rubber industry, this definition is widely identified with the term “modulus” and care should be taken to avoid confusion with the other use of “modulus” to denote the slope of the stress-strain curve at a given elongation.
3.8
tensile stress at yield
Sy
tensile stress (3.1) at the first point on the stress-strain curve where some further increase in strain occurs without any increase in stress
Note 1 to entry: This might correspond either to a point of inflection [see Figure 1 b)] or to a maximum [see Figure 1 c)].
3.9
elongation at yield
Ey
tensile strain at the first point on the stress-strain curve where some further increase in strain is not accompanied by an increase in stress
Note 1 to entry: See Figure 1.
Figure 1 — Illustration of tensile terms
graphic
a)
graphic
b)
graphic
c)
Key
E elongation Sy stress at yield
Eb elongation at break TS tensile strength
Ey elongation at yield TSb tensile strength at break
S stress Y yield point
3.10
test length of a dumb-bell
initial distance between reference points within the length of the narrow portion of a dumb-bell test piece used to measure elongation (3.2)
Note 1 to entry: See Figure 2.
Bibliography
[1]
ISO 5725-3, Accuracy (trueness and precision) of measurement methods and results — Part 3: Intermediate measures of the precision of a standard measurement method
[2]
ISO 6072, Rubber — Compatibility between hydraulic fluids and standard elastomeric materials
[3]
ISO/TR 9272, Rubber and rubber products — Determination of precision for test method standards
[4]
ISO 13226, Rubber — Standard reference elastomers (SREs) for characterizing the effect of liquids on vulcanized rubbers



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