GB/T 39693.4-2025 Rubber, vulcanized or thermoplastic—Determination of hardness—Part 4: Indentation hardness by durometer method (Shore hardness) English, Anglais, Englisch, Inglés, えいご
Rubber, vulcanized or thermoplastic - Determination of hardness - Part 4: Indentation hardness by durometer method (Shore hardness)
WARNING 1 - 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 the 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.
1 Scope
This document 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 D scale for rubbers in the high-hardness range;
- the AO scale for rubbers 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 following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. 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 - Determination of hardness - Part 9: Calibration and verification of hardness testers
Note: GB/T 39693.9-2021, Rubber, vulcanized or thermoplastic - Determination of hardness - Part 9:Calibration and verification of hardness testers (ISO 48-9:2018, IDT)
ISO 23529 Rubber - General procedures for preparing and conditioning test pieces for physical test methods
Note: GB/T 2941-2025, Rubber - General procedures for preparing and conditioning test pieces for physical test methods (ISO 23529:2016, IDT)
3 Terms and definitions
No terms and definitions are listed in this document.
4 Principle
An indentor of specified dimensions is pressed into a test piece under a specified load and the depth of indentation measured. This indentation is converted to a hardness value by means of a specified relation.
5 Choice of durometer
When using durometers, the scale should be chosen as follows:
- for values less than 20 with a type D durometer: type A;
- for values less than 20 with a type A durometer: type AO;
- for values over 90 with a type A durometer: type D;
- for thin test pieces (less than 6 mm thick): type AM.
6 Apparatus
6.1 Durometer types A, D and AO
These durometers consist of the components specified in 6.1.1 to 6.1.5.
6.1.1 Pressure foot
The pressure foot for types A and D shall have a diameter of 18 mm ± 0.5 mm and a central hole of diameter 3 mm ± 0.1 mm. For type AO, the pressure foot shall have a minimum area of 500 mm2 with a central hole of diameter 5.4 mm ± 0.2 mm. The tolerances on the dimension of the central hole and the requirement for the size of the pressure foot only apply to instruments used on a stand.
6.1.2 Indentor
The indentor shall be formed from a hardened-steel rod of diameter 1.25 mm ± 0.15 mm to the shape and dimensions shown in Figure 1 for type A durometers and Figure 2 for type D durometers. Type AO durometers shall have a round indentor with a radius of 2.50 mm ± 0.02 mm in accordance with Figure 3.
6.1.3 Indicating device
This is a device for allowing the extent of protrusion of the point of the indentor beyond the face of the pressure foot to be read. It shall be calibrated directly in terms of units ranging from 0 for the maximum protrusion of 2.50 mm ± 0.02 mm to 100 for zero protrusion obtained by placing the pressure foot and indentor in firm contact with a suitable flat, hard surface (e.g. glass).
6.1.4 Calibrated spring
This is used to apply a force, F, expressed in millinewtons, to the indentor in accordance with one of the following formulae:
- For type A durometers:
where HA is the hardness reading taken from the type A durometer.
- For type D durometers:
