JIS K 6253 Rubber, Vulcanized or Thermoplastic - Determination of Hardness

The standard “JIS K 6253 Rubber, vulcanized or thermoplastic - Determination of hardness” developed by the Japanese Industrial Standards organization (JIS) consists of a series of standards organized under the same title:

• The standard “JIS K 6253-1 Part 1: General guide” describes the general rules for determining the hardness of vulcanized rubber and thermoplastic rubber. This standard aims to provide types of methods for determining the hardness of vulcanized rubber and thermoplastic rubber and to assist in selecting a suitable method.

This standard is essentially based on the standard "ISO 18517 Rubber, vulcanized or thermoplastic - Hardness testing - Introduction and guidance" developed by the International Organization for Standardization (ISO). This international standard provides guidance for the determination of the hardness of vulcanized and thermoplastic rubbers. It is designed to provide an understanding of the importance of hardness as a material property and to assist in the selection of an appropriate test method.

• The standard “JIS K 6253-2 Part 2: IRHD method (Hardness between 10 IRHD and 100 IRHD)” describes methods for determining the international rubber hardness grade (IRHD) of vulcanized or thermoplastic rubbers. The methods specified in this standard cover the hardness range from 10 IRHD to 100 IRHD. This standard does not specify a method for determining IRHD with an IRHD pocket hardness meter.

This standard is essentially based on the International Organization for Standardization (ISO) standard "ISO 48-2 Rubber, vulcanized or thermoplastic - Determination of hardness - Part 2: Hardness between 10 IRHD and 100 IRHD". This international standard specifies four methods for the determination of the hardness of vulcanized or thermoplastic rubbers on flat surfaces (standard hardness methods) and four methods for the determination of the apparent hardness of curved surfaces (apparent hardness methods). Hardness is expressed in international rubber hardness grades (IRHD). The methods cover the hardness range from 10 IRHD to 100 IRHD. These methods differ primarily in the diameter of the indented ball and the magnitude of the indentation force, and these are selected to suit the particular application.

This standard specifies four methods for determining standard hardness:

• Method N (normal test): Suitable for rubbers with hardness in the range of 35 IRHD to 85 IRHD, but can also be used in hardnesses in the range of 30 IRHD to 95 IRHD.
• Method H (high hardness test): Suitable for rubbers with hardness in the range of 85 IRHD to 100 IRHD.
• Method L (low hardness test): Suitable for rubbers with hardness in the range of 10 IRHD to 35 IRHD.
• Method M (microtesting): Essentially a scaled-up version of the regular test method N, allowing thinner and smaller test pieces to be tested. Suitable for rubbers with hardnesses in the range of 35 IRHD to 85 IRHD, but can also be used for hardnesses in the range of 30 IRHD to 95 IRHD.

This standard also specifies four methods for determining the apparent hardness of curved surfaces, namely CN, CH, CL and CM. These methods are modifications of the above methods and are used when the rubber surface being tested is curved, in which case there are two possibilities:

• The test piece or product being tested is large enough that the hardness tester can rest on it.
• The test piece or product under test is small enough that both the test piece and the instrument can rest on a common support.

Apparent hardness can also be measured on non-standard flat test pieces using the N, H, L and M methods.

• The standard “JIS K 6253-3 Part 3: Durometer method” describes a method for determining the hardness of vulcanized or thermoplastic rubber using hardness meters.

Essentially, this standard is based on the standard “ISO 48-4 Rubber, vulcanized or thermoplastic - Determination of hardness - Part 4: Indentation hardness (Shore hardness) by the durometer method” developed by the International Organization for Standardization (ISO). This international standard includes a method for determining the indentation hardness (Shore hardness) of vulcanized or thermoplastic rubber using durometers with the following scales:

• A scale for rubbers in the normal hardness range
• D scale for rubbers in the high hardness range
• AO scale for low hardness rubbers and cellular rubbers
• AM scale for thin rubber test pieces in the normal hardness range

This standard is essentially based on the standard "ISO 7619-2 Rubber, vulcanized or thermoplastic - Determination of indentation hardness - Part 2: IRHD pocket measurement method" developed by the International Organization for Standardization (ISO). This international standard includes a method for determining the indentation hardness of vulcanized or thermoplastic rubber by means of a pocket hardness meter calibrated in IRHD. The use of such meters is primarily for control purposes and not for specification purposes (ISO 48 standard applies for specification). It is possible to increase the accuracy by fixing the pocket hardness meter to a support.

• “JIS 6253-5 Part 5: Calibration and verification of hardness tester” is based on the International Rubber Hardness (IRHD) testing machine. Durometer (JIS K 6253-3) and IRHD pocket hardness tester (JIS K 6253-4) are used for calibration and verification.

This standard is essentially based on the standard “ISO 18898 Rubber - Calibration and verification of hardness testing instruments” developed by the International Organization for Standardization (ISO). This international standard includes procedures for the calibration and verification of hardness testers of types A, D, AO and AM as defined in ISO 7619-1, IRHD pocket gauges as defined in ISO 7619-2, IRHD dead load instruments as defined in ISO 48 and dead load instruments using the very low rubber hardness scale as defined in ISO 27588.

Among the numerous tests, measurements, analyses and evaluation studies carried out for businesses in various sectors, our organization also provides testing services defined in the standard “JIS K 6253 Rubber, vulcanized or thermoplastic - Determination of hardness” with its trained and expert staff and advanced technological equipment.