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Ref. No. : lSO/R 868-1968(E)
UDC 678.51.8 : 620.178.15
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IS0
IN TE RN AT1 ON A L ORGAN I Z AT I O N FOR STAND A RD IZATl O N
IS0 RECOMMENDATION
R 868
PLASTICS
DETERMINATION OF INDENTATION HARDNESS OF PLASTICS
BY MEANS OF A DUROMETER (SHORE HARDNESS)
1st EDITION
November 1968
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation K 868, Plastics - Determination of indentation hardness uj'plastics by meatis
of a durumeter (Shore hardness), was drawn up by Technical Committee ISO/TC 61, Plastics, the Secretariat
of which is held by the United States of America Standards Institute (USASI).
Work on this question led, in 1965. to the adoption of a Draft IS0 Recornmendation
In September 1966, this Draft IS0 Recommendation (No YSX) was circulated to all the IS0 Member
Bodies for enquiry. It was approved, subject to a few modificatioris of an editorial nature. by the following
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Member Bodies :
Australia India South Africa, Rep. of
Austria I ran Spain
Belgium Ireland Sweden
Brazil Israel Switzerland
Bulgaria Italy Thailaiid
Canada Japan Turkey
Chile
Korea, Rep. of [J.A.R.
Czechoslovakia
Net herlands United Kingdom
Finland Polar id
IJ .s .A.
Germany Portugal U .S .S.K.
Hungary
Kornania
'I WO Member Bodies opposed the approval of the Draft :
France
New Zealand
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 ('ouncil, which
decided, in November 1968, to accept it as an IS0 RECOMMENDATION.
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ISO/R 868-1968 (E
IS0 Recommendation R 868 November 1968
PLASTICS
DETERMINATION OF INDENTATION HARDNESS OF PLASTICS
BY MEANS OF A DUROMETER (SHORE HARDNESS)
1. SCOPE
1.1 This IS0 Recommendation describes the procedure for determining the indentation hardness of plastics
by means of durometers of two types; durometer Type A is used for softer plastics and durometer Type D
for harder plastics (see Note, clause 7.2). The method permits measurement either of the initial
indentation or of indentation after specified periods of time, or both.
NOTE. - The durometers and the methods described in this IS0 Recommendation are referred to as Type A Shore and
Type D Shore durometers and durometer methods.
1.2 These methods are empirical tests intended primarily for control purposes. No simple relationship exists
between indentation hardness determined by this method and any fundamental property of the material
tested. For specification purposes, it is recommended that IS0 Recommendation R 48, Dereminution of
hardness of vulcanized natural and synthetic rubbers, should be used for the softer materials.
2 PRiNCIPLE
This method measures the penetration of a specified indenter forced into the material under specified conditions.
The indentation hardness is inversely related to the penetration and is dependent on the modulus of elasticity and
the viscoelastic properties of the material. The shape of the indenter and the force applied to it influence the results
obtained so that there may be no simple relationship between the results obtained with one type of durometer
and those obtained with either another type of durometer or another instrument for measuring hardness.
3. APPARATUS
The durometers, Types A and D, consist of the following components :
3.1 Presserfoot, with a hole between 2.5 and 3.5 mm in diameter, centred at least 6 mm from any edge of the
foot.
3.2 Indenter, formed from a hardened steel rod between 1.10 and 1.40 mm in diameter to the shape and
dimensions shown in Figure 1, for Type A durometers, and Figure 2, for Type D durometers.
3.3 Indicaring device, for reading the extent of protrusion of the point of the indenter beyond the face of the
presser foot; this may be read directly in terms of units ranging from zero, for the full protrusion of
2.50 k 0.04 mm, to 100, for nil protrusion obtained by placing the pressure foot and indenter in fm
contact with a flat piece of glass.
3.4 Calibrated spring, for applying force to the indenter in accordance with one of the foiiowiq equations :
Force in grammes-force = 56 + 7.66 HA
(a)
where HA is hardness reading on Type A durometer;
Force in grammes-force = 45.36 HD
(b)
where HD is hardness reading on Type D duromter.
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ISO/R 868 - 1968 (
4. TEST PIECE
4.1 For the determination of hardness by the Type A Shore durometer method, the test piece should be at
least 5 mm thick, and by the Type D Shore durometer method, at least 3 mm thick. A test piece may be
composed of thinner layers to obtain the necessary thickness, but determinations made on such test
pieces may not agree with those made on one-piece test pieces because the surfaces between plies may
not be in complete contact.
4.2 The dimensi
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