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`INTERNATIONAL
`STANDARD
`
`ISO
`48-4
`First edition
`2018-08
`
`Part 4:
`
`Rubber, vulcanized or
`thermoplastic — Determination of
`hardness —
`
`Indentation hardness by durometer
`method (Shore hardness)
`Caoutchouc vulcanisé ou thermoplastique - Détermination de la
`dureté —
`Partie 4: Dureté par pénétration par la méthode au duromètre
`(dureté Shore)
`
`Please share your feedback about
`the standard. Scan the QR code
`with your phone or click the link
`Customer Feedback Form
`
`Reference number
`ISO 48-4:2018(E)
`© ISO 2018
`
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`ISO 48-4:2018(E)
`
`
`COPYRIGHT PROTECTED DOCUMENT
`
`© ISO 2018
`All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
`be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
`on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
`below or ISO’s member body in the country of the requester.
`ISO copyright office
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`Published in Switzerland
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`ISO 48-4:2018(E)
`
`
`Contents
`
`Page
`Foreword ........................................................................................................................................................................................................................................iv
`Introduction ..................................................................................................................................................................................................................................v
`Scope .................................................................................................................................................................................................................................1
`Normative references ......................................................................................................................................................................................1
`Terms and definitions .....................................................................................................................................................................................1
`Principle ........................................................................................................................................................................................................................2
`Choice of durometer .........................................................................................................................................................................................2
`Apparatus .....................................................................................................................................................................................................................2
`6.1
`Durometer types A, D and AO ....................................................................................................................................................2
`6.1.1
`Pressure foot .......................................................................................................................................................................2
`6.1.2
`Indentor ...................................................................................................................................................................................2
`6.1.3
`Indicating device ..............................................................................................................................................................2
`6.1.4
`Calibrated spring .............................................................................................................................................................2
`6.1.5
`Automatic timing device (optional) ................................................................................................................5
`6.2
`Durometer type AM ............................................................................................................................................................................5
`6.2.1
`Pressure foot .......................................................................................................................................................................5
`6.2.2
`Indentor ...................................................................................................................................................................................5
`6.2.3
`Indicating device ..............................................................................................................................................................5
`6.2.4
`Calibrated spring .............................................................................................................................................................6
`6.2.5
`Automatic timing device (optional) ................................................................................................................6
`Stand ................................................................................................................................................................................................................6
`6.3
`6.4
`Durometer spring force calibration ......................................................................................................................................6
`Test pieces ...................................................................................................................................................................................................................7
`General ...........................................................................................................................................................................................................7
`7.1
`Thickness .....................................................................................................................................................................................................7
`7.2
`Surface ............................................................................................................................................................................................................7
`7.3
`Conditioning and test temperature ...................................................................................................................................................8
`Procedure.....................................................................................................................................................................................................................8
`9.1
`General ...........................................................................................................................................................................................................8
`9.2
`Test time .......................................................................................................................................................................................................8
`9.3 Measurements .........................................................................................................................................................................................8
`Calibration and checking .............................................................................................................................................................................8
`10.1 Calibration ..................................................................................................................................................................................................8
`10.2 Checking using standard rubber blocks ..........................................................................................................................9
`Precision .......................................................................................................................................................................................................................9
`Test report ...................................................................................................................................................................................................................9
`Annex A (informative) Precision ............................................................................................................................................................................10
`Bibliography .............................................................................................................................................................................................................................15
`
`1
`2
`3
`4
`5
`6
`
`7
`
`8
`9
`
`10
`
`11
`12
`
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`ISO 48-4:2018(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. Each 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.
`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).
`Attention is drawn to the possibility that some of the elements of this document may be the subject of
`patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
`any patent rights identified during the development of the document will be in the Introduction and/or
`on the ISO list of patent declarations received (see www .iso .org/patents).
`Any trade name used in this document is information given for the convenience of users and does not
`constitute an endorsement.
`For an explanation of the meaning of ISO specific terms and expressions related to conformity assessment,
`as well as information about ISO's adherence to the World Trade Organization (WTO) principles in the
`Technical Barriers to Trade (TBT) see the following URL: www .iso .org/iso/foreword .html.
`This document was prepared by Technical Committee ISO/TC 45, Rubber and rubber products,
`Subcommittee SC 2, Testing and analysis.
`This first edition of ISO 48-4 cancels and replaces ISO 7619-1:2010 which has been technically revised.
`The main changes compared to the previous edition are as follows:
`— a new standard number has been given.
`—
`in the Introduction, an explanation of the purpose of the grouping work has been added.
`—
`in 6.3.1, the description has been improved to distinguish hand-held instruments and on-a-stand
`instruments more clearly.
`—
`in Clause 8, the description for the required time for conditioning has been improved for better
`understanding.
`—
`in 9.2, the use of talcum powder has been removed.
`—
`in Annex A, precision results from ITPs that were carried out in 1985 and 2007 have been included.
`A list of all parts in the ISO 48 series can be found on the ISO website.
`Any feedback or questions on this document should be directed to the user’s national standards body. A
`complete listing of these bodies can be found at www .iso .org/members .html.
`
`iv
`
`
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`ISO 48-4:2018(E)
`
`
`Introduction
`
`ISO/TC 45/SC 2 established a principle that it would be helpful for users if standards on the same subject
`but covering different aspects or methods were grouped together, preferably with an introductory
`guidance standard, rather than being scattered throughout the numbering system. This has been
`achieved for some subjects, for example curemeters (ISO 6502) and dynamic properties (ISO 4664).
`In 2017, it was decided to group standards for hardness and, subsequently, it was agreed that they
`would be grouped under the ISO 48 number. The new standards together with the previously numbered
`standards are listed below.
`— ISO 48-1: former ISO 18517
`— ISO 48-2: former ISO 48
`— ISO 48-3: former ISO 27588
`— ISO 48-4: former ISO 7619-1
`— ISO 48-5: former ISO 7619-2
`— ISO 48-6: former ISO 7267-1
`— ISO 48-7: former ISO 7267-2
`— ISO 48-8: former ISO 7267-3
`— ISO 48-9: former ISO 18898
`The hardness of rubber, as measured by a durometer (Shore hardness) or an IRHD pocket meter, is
`determined from the response of the rubber to an applied indentation. The response is complex and
`will depend on:
`a)
`the elastic modulus of the rubber;
`b)
`the viscoelastic properties of the rubber;
`c)
`the thickness of the test piece;
`d) the geometry of the indentor;
`e)
`the pressure exerted;
`f)
`the rate of increase of pressure;
`g)
`the interval after which the hardness is recorded.
`Because of these factors, it is inadvisable to relate results using a durometer (Shore hardness) directly to
`IRHD values, although correlations have been established for some individual rubbers and compounds.
`Durometers were originally portable hand-held instruments that have proved to be particularly
`convenient for making measurements on products. By now a lot of laboratories also use them on a stand
`with a weight applied to the pressure foot in order to improve precision significantly.
`NOTE
`ISO 48-2 specifies hardness measurements for determination of hardness between 10 IRHD and
`100 IRHD. Further information on the relationship between the durometer values and IRHD values is given in
`References [5][6][7].
`
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`INTERNATIONAL STANDARD
`
`ISO 48-4:2018(E)
`
`Part 4:
`
`Rubber, vulcanized or thermoplastic — Determination of
`hardness —
`
`Indentation hardness by durometer method (Shore
`hardness)
`WARNING 1 — Persons using this document should be familiar with normal laboratory practice.
`This document does not purport to address all of the safety problems, if any, associated with its
`use. It is the responsibility of the user to establish appropriate safety and health practices and to
`determine the applicability of any other restrictions.
`WARNING 2 — Certain procedures specified in this document might involve the use or generation
`of substances, or the generation of waste, that could constitute a local environmental hazard.
`Reference should be made to appropriate documentation on safe handling and disposal after use.
`
`1 Scope
`
`2 Normative references
`
`verification of hardness testers
`
`This document specifies a method for determining the indentation hardness (Shore hardness) of
`vulcanized or thermoplastic rubber using durometers with the following scales:
`— the A scale for rubbers in the normal-hardness range;
`— the D scale for rubbers in the high-hardness range;
`— the AO scale for rubbers in the low-hardness range and for cellular rubbers;
`— the AM scale for thin rubber test pieces in the normal-hardness range.
`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 48-9, Rubber, vulcanized or thermoplastic — Determination of hardness — Part 9: Calibration and
`ISO 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test methods
`No terms and definitions are listed in this document.
`ISO and IEC maintain terminological databases for use in standardization at the following addresses:
`— ISO Online browsing platform: available at https: //www .iso .org/obp
`— IEC Electropedia: available at https: //www .electropedia .org/
`© ISO 2018 – All rights reserved
`
`3 Terms and definitions
`
`
`
`1
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`ISO 48-4:2018(E)
`
`
`4 Principle
`
`5 Choice of durometer
`
`An indentor of specified dimensions is pressed into a test piece under a specified load and the depth
`of indentation measured. This indentation is converted to a hardness value by means of a specified
`relation.
`When using durometers, the scale should be chosen as follows:
`—
`for values less than 20 with a type D durometer: type A;
`—
`for values less than 20 with a type A durometer: type AO;
`—
`for values over 90 with a type A durometer: type D;
`—
`for thin test pieces (less than 6 mm thick): type AM.
`These durometers consist of the components specified in 6.1.1 to 6.1.5.
`The pressure foot for types A and D shall have a diameter of 18 mm ± 0,5 mm and a central hole of
`diameter 3 mm ± 0,1 mm. For type AO, the pressure foot shall have a minimum area of 500 mm2 with a
`central hole of diameter 5,4 mm ± 0,2 mm. The tolerances on the dimension of the central hole and the
`requirement for the size of the pressure foot only apply to instruments used on a stand.
`The indentor shall be formed from a hardened-steel rod of diameter 1,25 mm ± 0,15 mm to the shape
`and dimensions shown in Figure 1 for type A durometers and Figure 2 for type D durometers. Type AO
`durometers shall have a round indentor with a radius of 2,5 mm ± 0,02 mm in accordance with Figure 3.
`This is a device for allowing the extent of protrusion of the point of the indentor beyond the face of the
`pressure foot to be read. It shall be calibrated directly in terms of units ranging from 0 for the maximum
`protrusion of 2,50 mm ± 0,02 mm to 100 for zero protrusion obtained by placing the pressure foot and
`indentor in firm contact with a suitable flat, hard surface (e.g. glass).
`This is used to apply a force, F, expressed in millinewtons, to the indentor in accordance with one of the
`following formulae:
`— For type A durometers:
`F = 550 + 75HA
`where HA is the hardness reading taken from the type A durometer.
`— For type D durometers:
`
`6 Apparatus
`
`6.1 Durometer types A, D and AO
`
`6.1.1 Pressure foot
`
`6.1.2
`
`Indentor
`
`6.1.3
`
`Indicating device
`
`6.1.4 Calibrated spring
`
`2
`
`
`
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`
`F = 445HD
`where HD is the hardness reading taken from the type D durometer.
`— For type AO durometers:
`F = 550 + 75HAO
`where HAO is the hardness reading taken from the type AO durometer.
`NOTE
`The rubber industry uses the term equation for the relationships herein termed formula. The term
`formula is used to describe the table of ingredients in a rubber compound.
`Dimension in millimetres
`
` a The protrusion shown is valid for a reading of 0.
`
`Figure 1 — Indentor for type A durometer
`
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`
`Dimension in millimetres
`
` a The protrusion shown is valid for a reading of 0.
`
`Figure 2 — Indentor for type D durometer
`
`Dimension in millimetres
`
` a The protrusion shown is valid for a reading of 0.
`
`Figure 3 — Indentor for type AO durometer
`
`4
`
`
`
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`
`Dimension in millimetres
`
`Figure 4 — Indentor for type AM durometer
`
`6.1.5 Automatic timing device (optional)
`
` a The protrusion shown is valid for a reading of 0.
`The timer shall be automatically activated when the pressure foot is in contact with the test piece and
`shall indicate the end of the test time or lock the test value at its completion. Use of a timing device
`for the test time improves precision. When the instrument is used on a stand, the time tolerance shall
`be ±0,3 s.
`This durometer consists of the components specified in 6.2.1 to 6.2.5.
`The pressure foot shall have a diameter of 9 mm ± 0,3 mm and a central hole of diameter
`1,19 mm ± 0,03 mm.
`The indentor shall be formed from a hardened-steel rod of diameter 0,79 mm ± 0,025 mm to the shape
`and dimensions shown in Figure 4.
`This is a device for allowing the extent of protrusion of the point of the indentor beyond the face of the
`pressure foot to be read. It shall be calibrated directly in terms of units ranging from 0 for the maximum
`protrusion of 1,25 mm ± 0,01 mm to 100 for zero protrusion obtained by placing the pressure foot and
`indentor in firm contact with a suitable flat, hard surface (e.g. glass).
`
`6.2 Durometer type AM
`
`6.2.1 Pressure foot
`
`6.2.2
`
`Indentor
`
`6.2.3
`
`Indicating device
`
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`6.2.4 Calibrated spring
`
`6.2.5 Automatic timing device (optional)
`
`6.3 Stand
`
`This is used to apply a force, F, expressed in millinewtons, to the indentor in accordance with the
`formula:
`F = 324 + 4,4HAM
`where HAM is the hardness reading taken from the type AM durometer.
`NOTE
`The rubber industry uses the term equation for the relationships herein termed formula. The term
`formula is used to describe the table of ingredients in a rubber compound.
`The timer, if used, shall be automatically activated when the pressure foot is in contact with the test
`piece and shall indicate the end of the test time or lock the test value at its completion. Use of a timing
`device for the test time improves precision. The time tolerance shall be ±0,3 s.
`6.3.1 The original concept of a durometer was a portable instrument that could be used, for example,
`on a product in service. However, better precision can be expected by using a stand with a weight centred
`on the axis of the indentor to apply the pressure foot to the test piece. Durometer types A, D and AO may
`be used either as hand-held instruments or mounted on a stand. Type AM durometers shall always be
`mounted on a stand. Clearly, when a stand is used, the portability is lost.
`NOTE
`As a general trend, it can be expected that the precision will follow the order:
`Hand held durometer < Hand held durometer equipped with force-calibrated hand-grip < Durometer using a
`stand < Durometer equipped with a timer and using a stand.
`Precision is affected by a number of factors, including parallax error, time of load application, speed of
`applying the load to the foot and orientation of the test piece. A detailed study of the reproducibility of
`rubber hardness tests can be found in Reference [8].
`6.3.2 The operating stand shall be capable of supporting the pressure-foot surface of the durometer
`parallel to the test piece support table.
`6.3.3 The stand shall be capable of applying the test piece to the indentor, or vice versa, without shock.
`NOTE
`A maximum speed of 3,2 mm/s has been found to be suitable.
`6.3.4 The total mass of the durometer and extra mass to overcome the spring force shall be:
`— 1
` kg for types A and AO;
`— 5
` kg for type D;
`— 0 25
` kg for type AM.
`The force values shall be in accordance with Table 1.
`
`1+ ,
`
`00
`
`5+ ,
`
`00
`
`,+
`05
`
`00
`
`,
`
`6.4 Durometer spring force calibration
`
`6
`
`
`
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`ISO 48-4:2018(E)
`
`
`Table 1 — Durometer spring forces
`
`Type AM
`
`mN
`Type A and AO
`
`Spring force
`550
`1 300
`2 050
`2 800
`3 550
`4 300
`5 050
`5 800
`6 550
`7 300
`8 050
`75
`±37,5
`
`Type D
`
`—
`4 450
`8 900
`13 350
`17 800
`22 250
`26 700
`31 150
`35 600
`40 050
`44 500
`445
`±222,5
`
`Indicated durometer value
`
`0
`10
`20
`30
`40
`50
`60
`70
`80
`90
`100
`Millinewtons (mN) per unit
`
`Spring force tolerance
`
`7 Test pieces
`
`7.1 General
`
`7.2 Thickness
`
`7.3 Surface
`
`324
`368
`412
`456
`500
`544
`588
`632
`676
`720
`764
`4,4
`±8,8
`Test pieces shall be prepared in accordance with ISO 23529.
`For the determination of hardness using type A, D and AO durometers, the thickness of the test piece
`shall be at least 6 mm.
`For the determination of hardness using type AM durometers, the thickness of the test piece shall be at
`least 1,5 mm.
`For sheets thinner than 6 mm and 1,5 mm (see above), the test piece may be composed of not more than
`three layers, in order to obtain the necessary thickness. However, determinations made on such test
`pieces might not agree with those made on single-layer test pieces.
`For comparative-test purposes, the test pieces shall be similar.
`NOTE
`Measurements made on thin test pieces of soft rubber will be influenced by the support table and will
`give a result which is too high.
`The other dimensions of the test piece shall be sufficient to permit measurements at least 12 mm away
`from any edge for types A and D, and 15 mm and 4,5 mm away from any edge for type AO and type AM,
`respectively.
`The surface of the test piece shall be flat and parallel over an area sufficient to permit the pressure foot
`to come into contact with the test piece over an area having a radius of at least 6 mm from the indentor
`point for types A and D, 9 mm for type AO and 2,5 mm for type AM.
`Satisfactory hardness determinations cannot be made on rounded, uneven or rough surfaces using
`durometers. However, their use in certain specialized applications is recognized, e.g. ISO 48-7 for the
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`ISO 48-4:2018(E)
`
`
`8 Conditioning and test temperature
`
`9 Procedure
`
`9.1 General
`
`9.2 Test time
`
`determination of the hardness of rubber-covered rolls. In such applications, the limitations to their use
`shall be clearly identified.
`For all test purposes, the minimum time between vulcanization and testing shall be 16 h. Where
`practical, test pieces shall be conditioned immediately before testing for a minimum period of 1 h at one
`of the standard laboratory temperatures specified in ISO 23529. The same temperature shall be used
`throughout any single test or series of tests intended to be comparable.
`Place the test piece on a flat, hard, rigid surface (e.g. glass). Apply the pressure foot to the test piece, or
`vice versa, as rapidly as possible but without shock, keeping the foot parallel to the surface of the test
`piece and ensuring that the indentor is normal to the rubber surface.
`Apply a force in accordance with 6.3.3 and 7.3 sufficient only to obtain firm contact between the
`pressure foot and the test piece and take the reading at the specified time after the pressure foot is
`in firm contact with the test piece. The standard test time is 3 s for vulcanized rubber and 15 s for
`thermoplastic rubber. Other test times may be used, provided they are stated in the test report. Rubbers
`of unknown types should be treated as vulcanized.
`NOTE 1
`A test time of 15 s has been introduced for thermoplastic rubber because the hardness value continues
`to decrease over a longer period of time than for vulcanized rubber, this test time being the same as that specified
`for plastics in ISO 868.
`NOTE 2
`If a flow curve is recorded for at least 15 s (hardness every 0,1 s) for an unknown material, the
`appropriate measuring time (3 s or 15 s) can be selected instead of treating it as vulcanized.
`Make three (known material) or five (unknown material) measurements of hardness at different
`positions on the test piece at least 6 mm apart for types A, D and AO and at least 0,8 mm apart for type
`AM, and determine the median value.
`If the time interval after which each reading was taken is different from 3 s, record the individual
`values of the indentation hardness together with the time interval after which each reading was taken,
`and determine the median value and the maximum and minimum values obtained.
`The instrument shall be calibrated regularly using suitable instruments for measuring force,
`indentation depth and indenter geometry in accordance with ISO 48-9.
`NOTE
`Abrasive material can strongly wear the indenter. Therefore, recalibration or replacement of the
`indenter can be needed more often than the standard frequency.
`
`9.3 Measurements
`
`10 Calibration and checking
`
`10.1 Calibration
`
`8
`
`
`
`© ISO 2018 – All rights reserved
`
`ClearCorrect Exhibit 1060, Page 14 of 22
`
`

`

`Licensed to Finnegan, Henderson, Farabow, Garrett & Dunner LLP / Aaron Sterngass (aaron.sterngass@finnegan.com)
`ISO Store Order: OP-877739 license #1/ Downloaded: 2025-02-25
`Single user licence only, copying and networking prohibited.
`
`ISO 48-4:2018(E)
`
`
`10.2 Checking using standard rubber blocks1)
`
`11 Precision
`
`12 Test report
`
`Press the instrument against a suitable flat, hard surface (e.g. glass) and adjust, where possible, the
`reading on the scale to give a value of 100.
`Continue the instrument check using a set of standard rubber blocks covering the measurement
`range. All adjustments shall be made in accordance with the manufacturer's instructions. The set
`of standard rubb