🔩 Tensile properties of rubber — tensile strength, elongation at break, stress at a given elongation; dumbbells of types 1, 1A, 2, 3, 4 and rings A, B; PN-ISO 37:2007 (ISO 37:2005), current ISO 37:2024

Materials and NDT PN-ISO 37:

Overview

WHAT THE STANDARD COVERS. Scope from the PKN card of PN-ISO 37:2007, in full (our translation): "Methods are described for determining: tensile strength, elongation at break, stress at a given elongation, elongation at a given stress and the yield point. The principle of the methods and guidance on the selection of test pieces in the form of rings and dumbbells are given. The test pieces, the apparatus, the test procedure and the method of calculating and expressing the results are described" (no full stop on the card). Scope of ISO 37:2024 (the same text in the evs.ee catalogue and in the extract of the standard), in the original wording: "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." We did not have the text of the Polish edition; we read the content of the method in the sample extracts of ISO 37:2024 (from the cover to clause 7.3, with the table of contents) and of ISO 37:2017 (from the cover to clause 7.5).

ACCORDING TO THE TEXT OF ISO 37:2024 (foreword, clauses 1–7.3). The standard was prepared by ISO/TC 45 "Rubber and rubber products", subcommittee SC 2 "Testing and analysis"; the seventh edition (2024-05) replaced the sixth (ISO 37:2017) — among other things a calibration schedule was added (Annex D, normative) and the symbols were changed in accordance with the ISO/IEC Directives, Part 2. References (2): ISO 5893 (constant rate of traverse testing machines), ISO 18899 (calibration of test equipment), ISO 23529:2016 (preparation and conditioning of test pieces). Definitions (3): stress S is calculated as the force per unit area of the ORIGINAL cross-section of the test length, elongation E — as a percentage of the test length; tensile strength Smax is the maximum stress up to break, and the tensile stress at break Sb may be lower than it, when after yield the elongation increases with falling stress; Eb — elongation at break; ES — elongation at a given stress; SE — stress at a given elongation, called the "modulus" in the rubber industry, which should not be confused with the slope of the stress-elongation curve; Sy and Ey — stress and elongation at yield. Principle (4): standard test pieces, dumbbells or rings, are stretched in a machine at a constant rate of traverse of the driven grip or pulley, reading force and elongation during the continuous stretching and at break. Choice of test piece (5): dumbbells and rings need not give the same values — in a stretched ring the stress is not uniform over the cross-section, and dumbbells may give different results depending on their direction relative to the direction of milling ("grain"). For tensile strength dumbbells are better — rings give lower, sometimes much lower, values. Elongation at break is approximately the same if for rings it is calculated from the original internal circumference and the dumbbells are cut perpendicular to the grain; the grain effect is studied only on dumbbells. For SE and ES the larger dumbbells (types 1, 2, 1A) are preferred; rings give approximately the same values when the elongation is calculated from the original mean circumference and for dumbbells the mean of cutting parallel and perpendicular to the grain is taken; rings may be preferable in automated testing, because they are easier to handle, and in determining the stress at a given strain. Test pieces (6): seven types — dumbbells 1, 2, 3, 4 and 1A and rings A (normal) and B (miniature); the results depend on the type, so different materials are compared only on the same type; miniature test pieces usually give higher tensile strength and elongation at break; buffing or levelling the thickness may change the result. Thickness of the narrow portion of the dumbbells: 2.0 mm ± 0.2 mm (types 1, 2, 3, 1A) or 1.0 mm ± 0.1 mm (type 4); test length (Table 1): 25 mm (type 1), 20 mm (types 1A and 2), 10 mm (types 3 and 4), all ± 0.5 mm; in test pieces from products the narrow portion may be at most 3.0 mm (types 1, 1A), 2.5 mm (types 2, 3) or 2.0 mm (type 4); types 3 and 4 are used only when material is insufficient — type 3 e.g. for pipe sealing rings and cable sheathing. Ring A: internal diameter 44.6 mm ± 0.2 mm, axial thickness and radial width 4 mm ± 0.2 mm; ring B: 8 mm ± 0.1 mm and 1 mm ± 0.1 mm, only when there is not enough material for ring A. Apparatus (7.1–7.3): dies according to ISO 23529, for dumbbells with the dimensions from Table 2 (e.g. type 1: overall length at least 115 mm, narrow portion 33 mm ± 2 mm long and 6.2 mm ± 0.2 mm wide), with a deviation from parallelism of the narrow portion of at most 0.05 mm; thickness gauge as in method A of ISO 23529:2016; cone gauge measuring the internal diameter of rings with an error of at most 0.01 mm.

ACCORDING TO THE TEXT OF ISO 37:2017 (clauses 7.4–7.5, which are not in the extract of the 2024 edition read). Machine according to ISO 5893 with force measurement accuracy of class 1; extensometer, if used — class D for dumbbells of types 1, 1A and 2 and class E for types 3 and 4; the machine must be capable of operating at least at rates of traverse of 100, 200 and 500 mm/min; when measuring the elongation of dumbbells a small pre-stress may be needed so that the test piece does not bend; at a temperature other than the laboratory temperature — a temperature-controlled chamber (guidance in ISO 23529). Rig for rings: two pulleys, one rotates freely with very low friction, the other is driven and rotates the ring at 10–15 rpm; the dimensions of the pulleys are given in Table 3. The foreword of ISO 37:2017 lists the changes compared with the fifth edition (ISO 37:2011): cutting edge angle of the die 30°–35°, corrected dimension B of the dumbbell, the class 1 requirement for force measurement, corrected pulley dimensions and added results of interlaboratory tests. How ISO 37:2005, which PN-ISO 37:2007 adopts, differs from these editions we DO NOT KNOW.

STATUS (as of 08.10.2026). The PKN card of PN-ISO 37:2007 (Polish version) has no withdrawal label: title "Rubber and thermoplastic rubber -- Determination of tensile stress-strain properties" (our translation), publication 14-03-2007, 28 pages, price group N, Chemistry Sector, KT 186 Rubber and Rubber Products, "Introduces: ISO 37:2005 [IDT]", "Replaces: PN-ISO 37:1998 - Polish version", ICS 83.060; in the field "Additional elements" — the corrigendum PN-ISO 37:2007/AC1:2008 (we have not read its content). PN-ISO 37:1998 (it introduced ISO 37:1994 and replaced PN-C-04205:1993) has the label "Withdrawn and replaced by PN-ISO 37:2007 - Polish version" and the withdrawal date 14-03-2007. PKN search, term "PN-ISO 37" (08.10.2026): only these two items with the number 37. On the ISO side: evs.ee catalogue — ISO 37:2024 in force since 17.05.2024, in the history ISO 37:2017 (since 10.11.2017); foreword of ISO 37:2024 — the seventh edition replaces the sixth (ISO 37:2017); foreword of ISO 37:2017 — the sixth edition replaces the fifth (ISO 37:2011). The Polish standard therefore adopts the 2005 edition, and PKN has not adopted the newer editions.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database and current PCA documents, read on 08.10.2026). The number appears in 11 records at 10 laboratories; in the current PCA documents (issues from 01.12.2025 to 27.07.2026) — in 11 entries at the same laboratories; none is suspended. Notations: "PN-ISO 37:2007+AC1:2008" — AB 005, AB 033 (with the addition "test pieces according to clause 6.1"), AB 067 and AB 169 (two entries); "PN-ISO 37:2007" and separately "PN-ISO 37:2007/AC1:2008" — AB 147 (alongside also ISO 37:2024) and AB 261; "PN-ISO 37:2007" without the corrigendum — AB 163 and AB 710; "ISO 37:2017-11" — AB 1814; "ISO 37" without a year — AB 128. At four laboratories the standard stands in one cell with standards for plastics (the PN-EN ISO 527 series, PN-EN ISO 6259) and other products: AB 005 (plastics, composites, rubber, pipes), AB 067 (electrotechnical materials and products), AB 163 (plastic pipes and fittings), AB 261 (plastics, rubber and metals, together with standards for cables and metals). The "Laboratories" tab searches for records beginning with "PN-ISO 37:" and shows 7 laboratories (8 entries); it does not show AB 128 ("ISO 37"), AB 1814 ("ISO 37:2017-11") or AB 005, at which the number stands in the middle of a long notation after the standards of the 527 series. The term without the colon would show 17 laboratories, ten of them only through standards with other numbers (PN-ISO 3733, PN-ISO 3754, PN-ISO 3771, PN-ISO 3795); that is why the entry searches with the colon.

WHAT THE LABORATORIES TEST (PCA documents). Quantities: tensile strength and elongation at break, at AB 147 and AB 169 also stress at a given elongation, and in the cells shared with standards for plastics (AB 067, AB 163) — the yield point. Subject: rubber and rubber products (AB 128; AB 147 — test pieces cut from vulcanized sheets or products; AB 1814), rubber and thermoplastic rubber (AB 710), rubber vulcanizate, conveyor belts and other vulcanized products (AB 169 — also the change in properties after accelerated heat ageing at 25–300 °C, together with PN-ISO 188:2000, PN-80/C-04238 and PN-EN ISO 868:2005), sole and upper materials for footwear — solid and microcellular rubbers, plasticized PVC compounds, thermoplastic rubbers, polyurethanes, EVA copolymers — and finished products (AB 033, a subject shared by several methods). Types of test pieces: AB 710 — type 1 and 1A, AB 128 — types 1 and 2, AB 1814 — type 2. Force ranges: 4–2000 N (AB 147), 10–1000 N (AB 033), up to 500 N (AB 128), up to 1 kN at an elongation of up to 230 mm (AB 169), machine 0.2–2500 N and extensometer 20–500 mm (AB 1814); in the cells shared with plastics — up to 300 kN and elongation up to 800 % (AB 005), up to 100 kN (AB 067, AB 163), up to 10 kN and relative elongation up to 1250 % (AB 261).

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. First — type of test piece: the results depend on the type, so only the same type is compared; rings give lower tensile strength than dumbbells, miniature test pieces usually higher values; a result without the type of test piece stated cannot be compared with another. Second — "modulus": SE, the stress at a given elongation, is called the "modulus" in the rubber industry, but it is not the slope of the stress-elongation curve. Third — cross-section: the stress is calculated on the area of the original cross-section of the test length. Fourth — Smax and Sb: after yield the stress may drop, and the stress at break is then lower than the tensile strength; these are two different quantities. Fifth — the edition: most laboratories cite PN-ISO 37:2007, i.e. ISO 37:2005; AB 147 gives ISO 37:2024 alongside it, and AB 1814 ISO 37:2017 alone; between the editions, among other things, the requirements for force measurement and dies changed (foreword of 2017) and a calibration schedule was added (2024); the notation "ISO 37" without a year (AB 128) does not say which edition is meant. Sixth — cells shared with standards for plastics: the scope of ISO 37 is vulcanized and thermoplastic rubber, and the document does not show which standard applies to which material; at AB 033 the subject also covers polyurethanes and EVA copolymers — whether they fall within the scope of ISO 37 we DO NOT DECIDE.

WHAT WE DO NOT GIVE. We did not have the text of PN-ISO 37:2007 (ISO 37:2005) or of the corrigendum AC1:2008. From ISO 37:2024 we do not have clauses 7.4–19 or the annexes: WE DO NOT GIVE the rates of stretching for the individual types of test pieces, the number of test pieces, the preparation and conditioning, the test temperature, the way of measuring the test pieces, the formulae (also for rings), the precision and the content of the report; from ISO 37:2017 we additionally have only clauses 7.4–7.5.

Method principle

Standard test pieces — dumbbells (types 1, 1A, 2, 3, 4) or rings (A, B) — are stretched in a tensile testing machine at a constant rate of traverse of the driven grip or pulley, and force and elongation are read during the continuous stretching and at break (ISO 37:2024, clause 4). The stress is calculated on the area of the original cross-section of the test length, the elongation — as a percentage of the test length; tensile strength, stress and elongation at break, stress at a given elongation, elongation at a given stress and, for some thermoplastic rubbers, stress and elongation at yield are determined.

Applications

• Vulcanized and thermoplastic rubber — tensile strength and elongation at break; in the current accreditation scopes 10 laboratories, 11 entries
• Rubber products — conveyor belts, sole materials for footwear, test pieces cut from products (narrow portion of the dumbbell up to 3.0 mm for types 1 and 1A)
• Assessment of changes after heat ageing — together with an ageing standard (at AB 169 with PN-ISO 188:2000)
• With a small amount of material types 3 and 4 or ring B — type 3 e.g. for pipe sealing rings and cable sheathing

Key parameters

Standard

Standard number

PN-ISO 37:2007 (wersja polska; wprowadza ISO 37:2005 [IDT]) z poprawką PN-ISO 37:2007/AC1:2008

Title (PL)

Guma i kauczuk termoplastyczny — Oznaczanie właściwości wytrzymałościowych przy rozciąganiu

Title (EN)

Rubber, vulcanized or thermoplastic — Determination of tensile stress-strain properties

Step-by-step procedure

1. Choice of test piece

   For tensile strength and for studying the effect of the grain direction — dumbbells; for SE and ES — preferably the larger dumbbells (types 1, 2, 1A); rings may be preferable in automated testing; types 3 and 4 and ring B only when material is insufficient (ISO 37:2024, 5–6).

2. Cutting the test pieces

   With a die according to ISO 23529 with the dimensions from Table 2; buffing or levelling the thickness may change the result (6.1, 7.1). WE DO NOT GIVE the details of preparation and conditioning (clauses 10–11).

3. Measuring the dimensions

   Thickness of the narrow portion with a thickness gauge as in method A of ISO 23529:2016, internal diameter of the rings with a cone gauge (7.2–7.3); WE DO NOT GIVE the measurement rules of clause 13.

4. Stretching

   In a machine according to ISO 5893 at a constant rate of traverse; read force and elongation during stretching and at break (clause 4). WE DO NOT GIVE the rates for the individual types and the test temperatures (clauses 14–15).

5. Calculations

   Stress = force / area of the original cross-section of the test length; elongation in % of the test length (3.1–3.2). WE DO NOT GIVE the formulae of clause 16, also for rings.

6. Report

   State the edition of the standard and the type of test piece — results of different types are not comparable (6.1). WE DO NOT GIVE the content of the report from clause 19.

Required equipment and apparatus

Health and safety (OHS)

• The standard states that it does not describe all the hazards associated with its use; safety and health practices are established by the user (ISO 37:2024, warnings 1 and 2)
• TECHNICAL NOTE: the result depends on the type of test piece — only the same type is compared; SE, called the "modulus" in the rubber industry, is not the slope of the curve; PN-ISO 37:2007 is ISO 37:2005, and the current edition is ISO 37:2024 without a Polish edition

Frequently asked questions