The ISO 48 standard, published by the International Standards Organization (ISO), consists of the following sections under the main title of "Rubber, vulcanized or thermoplastic - Hardness determination":
The ISO 48-1 standard provides guidance for determining the hardness of vulcanized and thermoplastic rubbers. The purpose of this standard is to provide an understanding of the importance of hardness as a material property and to assist in the selection of an appropriate test method. For the purposes of this standard,
The ISO 48-2 standard describes four standard hardness methods for determining the hardness of vulcanized or thermoplastic rubbers on flat surfaces and four apparent hardness methods for determining the apparent hardness of curved surfaces. Hardness is expressed in international rubber hardness grades (IRHD). These hardness methods cover the hardness range of 10 IRHD to 100 IRHD.
The four methods for determining standard hardness are:
The four methods for determining apparent hardness ((CN, CH, CL, and CM methods) are modifications of the N, H, L, and M methods, respectively, and are used when the rubber surface being tested is curved.
The ISO 48-3 standard defines a dead load method for determining the hardness of very soft vulcanized or thermoplastic rubbers using a very low rubber hardness scale.
The ISO 48-4 standard describes a test method for determining the indentation hardness (Shore hardness) of vulcanized or thermoplastic rubber using durometers with the following scales:
The ISO 48-5 standard describes a test method for determining the indentation hardness of vulcanized or thermoplastic rubber by means of a pocket hardness meter calibrated in international rubber hardness grades (IRHD). The use of such meters is primarily for control purposes. It is possible to increase the sensitivity by fixing the pocket hardness tester to a support.
The ISO 48-6 standard describes a method for determining the apparent hardness of vulcanized or thermoplastic rubber roller covers, expressed in international degrees of rubber hardness (IRHD). This method is in principle similar to the methods used in ISO 48-2 to determine the hardness of rubber in that it essentially consists of measuring the penetration depth of a spherical indentor operating under a certain force.
The ISO 48-7 standard defines a method for determining the apparent hardness of vulcanized or thermoplastic rubber cylinder heads, expressed by Shore hardness, for measurements where only medium precision is required. The method and apparatus used are mainly those described in the ISO 48-4 standard.
The ISO 48-8 standard describes a method for determining the apparent hardness of vulcanized or thermoplastic rubber cylinder heads, expressed as the Pusey and Jones indentation value. The Pusey and Jones plastometer apparatus is used to measure the indentation depth of an indenter under a certain force into the rubber surface. The Pusey and Jones indentation value is an inverse measurement of hardness, meaning the harder the rubber, the lower the Pusey and Jones indentation value.
The ISO 48-9 standard describes procedures for the calibration and verification of durometers of types A, D, AO and AM, IRHD pocket measuring instruments, IRHD dead load instruments and constant load instruments using the very low rubber hardness scale.
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