ISO 48-4:2018 pdf free download.kubber, vulcanized or thermoplastic — Determination of hardness — Part 4: Indentation hardness by durometer method (Shore hardness).
ISO/TC 45/SC 2 established a principle that It woiiltl bi’ helpful [or users listandards on the same suhiect 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 br some subjeeLs. for exaniple curemeters liSt) 6502) and dynamic propcrties(lSO 4664).
In 2017. ii was decided to group standards for hardness and, subsequently, ii was agreed that they would he grouped under the ISO 49 number, The new st.indards together with the previously numbered standards are listed below.
— ISO 48.1: lormer ISO 18517
— ISO 411-2: former 1St) 411
— ISO 49-3: former ISO 27588
— ISO 49-4: former ISO 7619.1
— 1Sf) 411-5: former 1Sf) 7619-2
— 1Sf) 48-6: former 1St) 7267-1
— ISO 48-7: former ISO 7267-2
— ISO 48-11: former ISO 7267-3
— ISO 48-9: former 15(1 19898
The hardness of rubber, as measured by a durorneter (Shore hardness) or an IRHD pocket meter. is determined from the response of the rubber to an ipplied Indentation. The response is complex and will depend on:
a) the elastic modulus of the rubber;
h) the viscoclastic properties ot the rubber:
c) the thickness of the test piece;
il) the geometry of the indentor;
e) the pressure exerted:
f) the rate ol increase ol pressure;
g) the interval alter which the hardness is recorded.
Herause ol these factors, it is lnatlv isablc to relate results using a durometer (Shore hardness) directly Lu 114111) values, although correlations have hen established br some individual rubbers and compounds.
Durometers were originally portable hand-held instrumenis th.it have proved to he parilcularly convenient for making measurements on products. Ily now a lot of laboratories also use them on a stand with a weight applied to the pressure loot In order to improve precision significantly.
NOTE ISO 411.2 SpecIfies hardness measurements for determination of hardness between  and . Further infornialion on the relationship between the durometc’r values and fRill) values is given in
WARNIN(3 I — 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 lie 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.
I Scope
ISO 48-4 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 1) scale for rubbers in the high-hardness range;
— the AO scale br ruhlwrs in the low—hardness range and for cellular rubbers:
— the AM scale for thin rubber test pieces in the normal-hardness range.
2 Normative references
The lollowing documents are referred to in the text in such a way that some or all of their content constitutes requirements of ISO 48-4. 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 — t)eterniination of hardness — Port 9: Culibrat ion mid verification of hardness testers
ISO 23529, Rubber — General proceduresfrirprepurincj and conditiomny test pieces/or rkvsic’ul test suet liod
6.2.5 Automatic timing device (optional)
The timer, if used, shall be automatically activated when the pressure toot is in contact with the test piece and shall indicate the end of the Lest time or lock the test value at its completion. Use of a timing device for the test time improves precision. The Lime tolerance shall be ±0,3 s.
6.3 Stand
6.3.1 The original concept of a durorneter was a portable instrument that could be used, for example. on a product in service. llowevei better precision can be expected Lw using a stand with a weight centred on the axis of the indentor to apply the pressure foot to the test piece. L)urometer types A, I) and At) may he used either as hand-held instruments or mounted on a stand. Type AM durometers shall always he mounted on a stand. Clearly, when a stand is Lised, the portability is lost.
N0TI As a general trend, it can be expected that the preciswn will lollow the order:
hand held durometer Hand held durometer equipped with torce-calibrated hand—grip < i)urometer using a stand < Durnnwter 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 loot and orientation of the test piece. A detailed study of the reproducibility of rubber hardness tests can he lound in Reference FBI.
6.3.2 The operating stand shall be capable ol supporting (tie pressure-tiot surface oh the duroiiieter parallel to the test piece support table.
6.3.3 The stand shall he capable of applying the test piece to the indentor, or vice versa, without shock. N0’l’I A maximum speed oF 3,2 mm/s has been Found to he suitable.
6.3.4 The total mass of the durometer and extra mass to overcome the spring torce shall be:
9.2 Test time
Apply a force in accordance with 33 and 13 sufficient oniy to obtain Firm contact lwtveen the pressure loot and the test piece and take the reading at the speciFied time alter the pressure toot 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 he used, provided they arc stated in the test report. Rubbers of unknown types should be treated as vulcanized.
NOTE I Atesttimeof 15s has been introduced forthermoplastic rublwrhecatis hehardness valuecontinues to decrease over a longer period oltitne th.in for vulcanized rubber, this test time being the same as that specified for plastics in ISO 8611.
NOTE 2 It a flow curve is recorded tar at least 15 s (hardness every 0.1 s) for an unknown material, the appropriate measuring tltiw (3 s or 15 s) can be selected instead of treating it as vulcanized.
9.3 Measurements
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 M) and at least 0.8 mm apart (or type AM. and determine the median value.
If the time interval after which each reading was taken is different Ironi :i ,recortI the individual va I ties of t hi’ Indent at tori ha rdiiess together wit Ii (he time interval alter vti ich each reading was t a ken, and deterini aic the med ian value a rid the maxim u 01 a rid in I iii mu in vi lues oht a I iied.
10 Calibration and checking
10.1 Calibration
The instrument shall he calibrated regularly LI sing suitable in ments for measuring force, indentation depth and indenter geometry in accordance with ISO 48-9.
NOTE Abrasive material can strongly wear the indenter, Therefore, recalibrat ion or replacement of the indenter can be needed more often than the standard frequency.