ISO 48-2010 pdf free download.Rubber, vulcanized or thermoplastic Determination of hardness (hardness between 10 IRHD and 100 IRHD).
Introduction
The hardness test speófled in ISO 48 le intended to provide a rd measaxement of rubber sltffness, unlike hardness tests on other materiats which measure resistance to permanent deformation.
Hardness is measured from the depth of Indentation 01 a spherical rdentor, under a specified force, ioto a rubber test piece. An empirical relationship between depth of Wdentation and Young’s modulus for a perfectly elastic Isotropic malarial has been used 10 denve a hardness scale which cart conveniently be used for most rubbers.
When It is required to determine the value of Young’s modulus itself. It is expected that an appropnate test method be used. for example that described in ISO 7743.
The guide to hardness testing, ISO 18517, can also be a useful reference.
WARNING — Persons using this International Standard should be familiar with normal laboratory practice. ISO 48 does not purport to address all of the safety probisms, if any, associated with its us.. It is the responsibility of the user to establish appropriate safety and health practices and to
•nsur compliance with any national regulatory conditions.
CAUTION — Certain procedures specified in ISO 48 may involve the use or generation of substances, or the g.n.ration of waste, that could constitute a local nvironmental hazard. Reference should be made to appropriate documentation on safe handling and disposal after us..
I Scope
ISO 48 specifies four methods for the delermralion of the hardness of vulcanized ci thermoplastic rubbers on flat surfaces (standard-hardness methods) and four methods for the delermination of the apparent hardness of curved surfaces (apparent-hardness methods). The hardness is expressed in International rubber hardness degrees (IRHD), The methods cover the hardness range from 10 IRHD to
100 IRHD.
These methods dIffer prtoai1$y In the diameter of the indenting ball and the magnitude of the indenting force. these being chosen to suit the particular appcation. The range of applicatality of each method is indicated in FIgure 1.
ISO 48 does not specify a method for the determination of hardness by a pocitet hardness meter, which is described in ISO 1619-2
ISO 48 specifies the foIowng four methods for the determination of standard hardness.
— Method N (normal test) is appropriate for rubbers with a hardness in the range 35 IRHO to 85 IRHO, but can also be used for hardnesses In the range 30 IRHD to 95 IRHD.
— Method H (high-hardness test) is appropriate Ice rubbers with a hardness to the range 85 IRHD to
100 IRHD.
Method I (low-hardness test) is appropriate for rubbers with a hardness in the range 10 IRHD to
35 IRHO.
— Method M (microtest) is essentially a scaled-down version of the normal test method N, permittIng the testing of thinner and smaller test peeces. It is appropnite for rubbers Mth a hardness in the range 35 IRHO Ic 85 IRHO, but can also be used for hardnesses in the range 30 IRHO to 95 IRHD.
NOTE 1 The value of the hadnees obtained by method it wi5W the ranges 85 IRHD to 95 IRHO and 30 IRHI) to 35 IRHD night not agree precisely with that obtained using method H or method I.. respedively. The difference is not normay signifIcant for technical purposes.
NOTE 2 Because of various surface effects in the rubber and the postibduty of slight surface roughness (jxoduced, for exenipie. by bufltng), the nicrotest night not always give results agreeing with those obtained by the nomiai test.
ISO 48 also specifies four methods, CN, Cl-f, CL and CM, for the determination of the apparent hardness of curved saafaces These methods are modifications of methods N, H. L and M. respectivdy, and are used when the rubber surface tested is curved, r which case there are two possibulibes:
a) the test piece or produci tested is large enough for the hardness instrument to rest ion it or
b) the lest piece or product tested is sinai enough for both the test piece and the instrument to rest upon a common support.
A variant of b) would be where the test piece rests upon the specimen table of the instrument.
Apparent hardness can also be measured on non-standard flat test peces using methods N, H. I arid M.
The procedures described cannot provide for all possible shapes and d.nensions of test piece, but cover some of the commonest types, such as 0-rings.
ISO 48 does nof specify the determination of the apparent hardness of rubber-covered rollers, wtsch is specified in ISO 7287 (all parts).
X hardness (IRKO)
Method I and method CL.
b Methods N and Mend methods CN end CM.
C Method H and method CH.
FIgure 1 — Rang. of applicability
2 Normative references
The following referenced documents are indispensable far the application of ISO 48. For dated references, only th. edition cited applies, For Ls’Idaled references, the latest edition of the reFerenced document (including any amendments) applies.
ISO 18898, Rubber — Cekbrafton and ven6catlon of hardness testers
ISO 23529. Rubber — Gen.raf procedures for preparing arid conditioning teat pieces for physical test
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3 Terms and definitions
For the purposes of ISO 48, the following terms and definitions apply.
3.1
international rubber hardness degree scale
IRHO scale
hardness scale chosen so that 0 represents the hardness of material having a Young’s modulus of zero and
100 represents the hardness of a malarial of lriftnule Young’s modulus
NOTE 1 fcIowlng characleristlcs applying over most of the ncrmal rang. of hardnesses
a) one international rubber har&iess degree always represents approximately the same proportional difference in Young’s ntodt*is
b) for highly elaslic rubbers, the IRHD end Shore A scales ar, comparable.
3.2
standard hardness
hardness obtained using the procedures described In methods N, H. I arid M on test pieces of the standard thidcness end not less than the minimum lateral dimensions specified
NOTE Standard hardness is reported to the nearest whole number in IRHO
3.3
apparent hardness
hardness obtained using the procedures descobed in methods N, H, L and M on test pieces of non-standard dimensions, as well as hardness values obtained using methods CN, CH. CL and CM
NOTE I Apparent hardness ta reported to the neatest whole number Ii IRHO
NOTE 2 Values obtained by methods CN, CH, CL and CM are always given as apparent hardnesaes since tests are commordy made on me conIete article where th lt’ucknesi of the rubber cal vary arid, in many cases, the lateral dwnensions might not provele the rmnivium distance beheeen the mdenior and the edge necessary to eliriwiate edge efiects Thus the readings obtained do not in general coincide whi readings obtained on standard lest pieces as delbied In methods N. H, Land Moron a flat parallel-faced alth of lb. same liclwess as the arhcie Moreover, me reacleigs might depend appreciably on the method of support of the whole arid whether or not a presser foot is used Therefore, results obtamed on curved surfaces are arbitrary v,ea applicable only to test pieces or articles of one particular shape and of particular dimensions, and supported ii one pwil way, and In extreme cases such v.ies can differ from lb. standard hardness by as much as 10 IRHO Furthermore, surfaces that have been tiuffed or otherwise prepared to rurnove cloth martcings. etc., osi give sighey different hardness Values from those with a smooth. moulded
4 PrInciple
The hardness test consists In measunng the difference between the depths of indentation of a ball Into the rubber under a small contact force and a large (indenting) foroe From this drnerence. multiplied when using the microtest by the scale factor 6, the hardness in IRHD is obtained from Tables 3 to 5 or from graphs based on these tables or from a scale, reading dweclly In IRHO, calculated from the tables and fitted to the indentation-measuring instrument. These tables and curves are derived from the empirical relationship between indentation depth and hardness given In Annex A.
5 Apparatus
5.1 General
Calibration and verification of the apparatus shall be perfoi’m.d In accordance with ISO 18898.
5.2 Methods N, H, Land M
The essential parts of the apparatus are as specified In 5.2.1105.2.6. the appropriate dimensions and forces being shown in Table 1.
5.2.1 Vertical plunger, hav.ng a ngld ball or spherical surface on the lower end, and means for supporting the plunger so that the spherical tip is kept slightly above the surface of the annular foot prior to applying the contact force.
5.2.2 Means for applying a contact force and an additional indenting force to the plunger. making allowance for the mass of the plunger, enduding any fittings attached to It, and for the force of any sp.lng acting on it, so that the forces actually transmitted through the spherical end of the plunger are as specified.
5.2.3 Means for measuring the Increase in depth of indentation of the plunger caused by the Indenting force, either in metflc units or reading directly In IRHD.
The gauge employed may be mechanical, optical or electrical
5.2.4 Flat annular fool normal to the axis of the plunger and havmg a central hole for the passage of the plunger.
The foot rests upon the test piece and exerts a pressure on Ii of 30 kPa ±5 kPa pt’ovlded that the total load on the loot does not fail outside the values given In Table 1. The foot shall be rigidly connected to the lndentation.measuring device. so that a measurement is made of the movement of the plunger relative to the foot (i.e. the top surface of the test piece), not relative to the surface supporting the test piece.
Table 1 — Forces and dimensions of apparatus
NOTE I In the .,…..4ol. when using kth,neile in which the lest piecs lotte a preseed upweds by a spnrç. the value. 0( the fool pressure end 5* tot. on me tact we those acting diJing me period of applcallon ol the total foivi Defoe 5* mosntlng love of 145 mNis epØ, the Ics on the oats greeter by 5* a,noisd. and heave equab 3 raN 530 n*J.
NOTE 2 Not all poae5* ccm(Wwiior. of dinene4ons end totes given in thee talte *41 meet V* p’eseue requirements c(524.
5.2.5 Means for gently vibrating the apparatus, for exempt. an electrically operated buzzer, to overcome any slight friction.
(Thes may be omitted In Instruments where friction Is effectively eliminated.)
5.2.6 Chamber for the test piece, when tests are made at temperatures other than a standard laboratory temperature.
This chamber shall be equipped with a means of maintaining the temperature within 2 C of the des#ed value The foot and vertical plunger shall extend through the top of the chamber, arid the portion passing through the top shall be constructed from a matenal having a low thermal conductivity A sensrng device shalt be located within the chamber near or at the location of the test piece, lot measLaing the temperature (see ISO 23529).
5.3 Methods CN, CH, CL and CM
The apparatus used shall be essentially that described In 5.2 but differing In the following respects.
5.3.1 CylIndrical surfaces of radius greater than 50 mm
The base of the instrument shall have a hole below the plunger, allowing free passage of me annular fool such that measurement may be made above or below the base.
The lower surface of the base shall be In the form of two c)Ilnders parallel to each other and the plane of the base. The diameter of the cinders and thel distance apart shall be such as to locate and support the itisbuinerit on the curved surface to be tested. 5Jtematively. the modified bass may be fitted with feet movable ii universal joints so that they adapt themselves to the curved surface
5.3.2 Surfaces with double curvature of larg. radius greater than 50 mm
The InstrwTierit with adjustable feet described in 5.3.1 shalt be Used.
5.3.3 CylIndrical surfacs of radius 4 mm to 50 mm or small test pieces with double curvature
On surfaces too small to support the instrument, the test piece or article shall be supported by means of special jigs or V-blocks so that the Indenlot Is vertically above the lest surface Wax may be used to fix small items to the test piece table.
In general. an instrument as descnbed for method M should be used ooly w$iere the thickness of the rubber tested is less than 4 mm.
NOTE Inatnirnents for method M in wiwch the test piece table pressed upwards by a spring are nat suitable far use an large lest pieces or aracles atm a large rius of curvature.
5.3.4 Small 0-rings and articles of radius of curvature less than 4 mm
These shall be held In suitable jigs or blocks or secured by wax to the Instrument table. Measurements shall be made using the instrument for method M
No test shall be made it the smallest radius is less than 0,8 mm.
6 Test pieces
6.1 General
Test pieces shall be prepared In accordance with ISO 23529.
6.2 Methods N, H, Land U
62.1 General
The test pieces shall have theE upper and lower surfaces flat, smooth and parallel to one another.
Tests intended to be comparable shall be made on test pieces ot the same thickness.
6.22 ThIckness
622.1 Methods N and H
The standard test piece shall be 8 mm to 10mm thick and shall be made up 01 one or more layers 01 rubber. the thinnest 01 which shall not be less than 2 mm thick, All surfaces shall be flat and parallel.
Non-standard test pieces may be either thicker or thinner, but not less than 4 mm thick.
62.2.2 Method I
The standard test piece shall be 10mm to 15mm thick and shall be made up of one or more layers of rubber. the thinnest of which shall not be less than 2 mm thick. All surfaces shall be flat and parallel,
Non-standard test pieces may be either thicker or thinner, but not less than 6 mm thick.
62.2.3 Method M
The standard test piece shall have a thickness 012mm ± 0,5 mm. Thicker or thinner test pieces may be used. but in no case less than 1 mm thick, Readings made on such test pieces do not in general agree with those obtained on the standard test piece.
6.2.3 Lateral dimensions
6.2.3.1 Methods N, H and L
The lateral dimensions of both standard and non-standard test pieces shall be such that no test is made at a distance from the edge of the test piece less than the appropriate distance shown In Table 2.
When test pieces thicker than 4 mm are tested on the mroest instrument because the lateral dimensaons or the avallable hat area do not permit testing on a normal instrument, the test shall be made at a distance from the edge as West as possible.
6.3 Methods CN. CII. CL and CM
The test piece shall be either a complete article or a piece cut therefrom, The underside of a cut piece shall be such that it can be property supported dunng the hardness test If the surface on which th test is to be made is cloth-marired, it shall be buffed prior to testlng Test pieces shall be alowed to recover at a standard laboratory temperature (see ISO 23529) for at least 16 I, after buffing and shall be conditioned in accordance with Clause 8. The conditioning period may form part of the recovery period.
7 Time interval between vulcanization and testing
Unless Otherwise specified for technical reasons, the following requrements shall be observed (see
ISO 23529):
– For all normal test purposes, the minimum time between vulcanization and testing shall be 16 h. In cases of arbitration, the minimum lime shall be 72 h.
— For non-product tests, the maximum time between vulcanization and testing shalt be 4 weeks and, for evaluations Intended to be comparable, the tests. as far as possible, shall be carried out alter the same time interval.
— For product tests, whenever po6sllle, the time between vulcanization and testing shall not exceed 3 months. In other cases, tests shall be made wIthin 2 months of the date of receipt by the purchaser of the product.
8 CondItioning of test pieces
8.1 When a test Is made at a standard laboratory temperature (see ISO 23529), the test pieces shall be maintained at the conditions of test foe at least 3 h immediately before testing.
8.2 When tests are made at higher or lower temperatures, the test pieces shall be maintained at the conditions of test for a period of lime sufficient to reach temperature equilibrium with the testing environment. or for the period of time reilred by the specification oovenng the material or product being tested, and then immediately tested.
9 Temperature of test
The test shall normally be carried out at standard laboratory temperature (see ISO 23529). When other temperatures are used, these shall be selected from the list of preferred temperatures specified In ISO 23529
10 Procedure
Condition the test piece as spedfled in Clause 8.
Lightly dust the upper and lower surfaces of the test piece with dusting powder. Place the test piece on a horizontal rigid surface. Bring the foot into contact with the surface of the test piece. Press the plunger end indenting ball for Sc on to the rubber, the force on the ball being the contact force.
NOTE Talc ties been taind lobe a iuitabls clusling pawder
If the gauge Is graduated in IRHD, adjust It to read 100 at the end of the 5s period; then apply the additional indenting force and maintain lot 30s, when a died readuig of the hardness in IRHO is obtained.
If the gauge is graduated in metric uMs. note the differential indentation I) (in hundredths of a millimetre) of the plunger caused by the additional indenting force, applied for 30 s. Convert this (after multiplying by the scale factor of 6 when using the apparatus for the microtest) Into IRHO, usig Tables 3 to 5 or a graph constructed therefrom.
Durmg the loading penods, vibrate the apparatus gently unless it is essentially free of friction.
11 Number of readings
Make one measurement at each of a minimum of three different points distributed over the test piece and separated from each other by a minimum of 6mm, and take the median of the results when these are arranged In increasing order.
12 Expression of results
Express the hardness, to the nearest whole number, as the median of the individual measurements in IRHD. indicated by the degree sign () followed by
a) either the letter S indicating that the test piece was of the standard thickness or. for tests on non-standard lest pieces, the actual test piece thickness end the smaller lateral dimension (in milimetres) (the result then being an apparent hardness):
b) the code-letter for the method, I.e. N for the normal test, H lot the high-hardness test. L for the low-hardness test arid fbi for the miuolest
C) for tests on curved surfaces, the prefix letter C.
EXAMPLE 1 5, SN
EXAMPLE2 16, BxZ5mm,t.
EXAMPI&3 90. CH
13 Precision
Precision results of inierlaboiatoq, test programmes (FTPS) are given in Mnex B.
14 Test report
The lest report shalt include the following particulars:
a) a reference to this International Standard (ISO 48:2010);
b) lest piece details:
1) the dinensions of the test piece,
2) the number of layers and the thicluiess of the thinnest layer.
3) In the case of curved or irregularty shaped test pieces, a desaiplion of the test piece.
4) the method of preparatIon of the test piece from the sample. for example moulded, butted, cut out,
5) details of the compound and the cure, where appropnate;
c) lest method:
1) the method used,
2) for curved lest pieces, the way In wtiioh the test piece was mounted;
d) lest details:
1) the ume and temperature of conditioning prior to testing,
2) the tempeiature of test, and the relative hemedey. if necessary.
3) any deviation from the procedure spec Itled.
e) lest results:
1) the number of lest pieces.
2) the individual lest results,
3) the median of the individual results, expressed as in Clause 12;
f) the date of the test.