ASTM D2240

This test method is based on the penetration of a specific type of indentor when forced into the material under specified conditions. The indentation hardness is inversely related to the penetration and is dependent on the elastic modulus and viscoelastic behavior of the material. The geometry of the indentor and the applied force influence the measurements such that no simple relationship exists between the measurements obtained with one type of durometer and those obtained with another type of durometer or other instruments used for measuring hardness. This test method is an empirical test intended primarily for control purposes. No simple relationship exists between indentation hardness determined by this test method and any fundamental property of the material tested. For specification purposes, it is recommended that Test Method D 785 be used for materials other than those described in 1.1.

FIG. 1 (a) Type A and C Indentor

FIG. 1(b) Type B and D Indentor (continued)

FIG. 1(c) Type O, DO, and OO Indentor (continued)

FIG. 1(d) Type M Indentor (continued)

FIG. 1(e) Type OOO Indentor (continued)

FIG. 1(f) Type OOO-S Indentor (continued)

FIG. 1(g) Type E Indentor (continued)

1. Scope

1.1 This test method covers twelve types of rubber hardness measurement devices known as durometers: Types A, B, C, D, DO, E, M, O, OO, OOO, OOO-S, and R. The procedure for determining indentation hardness of substances classified as thermoplastic elastomers, vulcanized (thermoset) rubber, elastomeric materials, cellular materials, gel-like materials, and some plastics is also described.

1.2 This test method is not equivalent to other indentation hardness methods and instrument types, specifically those described in Test Method D 1415.

1.3 This test method is not applicable to the testing of coated fabrics.

1.4 All materials, instruments, or equipment used for the determination of mass, force, or dimension shall have traceability to the National Institute for Standards and Technology, or other internationally recognized organizations parallel in nature.

1.5 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only. Many of the stated dimensions in SI are direct conversions from the U. S. Customary System to accommodate the instrumentation, practices, and procedures that existed prior to the Metric Conversion Act of 1975.

1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents

ASTM Standards
D1349 Practice for Rubber--Standard Temperatures for Testing
D1415 Test Method for Rubber Property--International Hardness
D374 Test Methods for Thickness of Solid Electrical Insulation
D4483 Practice for Determining Precision for Test Method Standards in the Rubber and Carbon Black Industries
D618 Practice for Conditioning Plastics for Testing
D785 Test Method for Rockwell Hardness of Plastics and Electrical Insulating Materials
F1957 Test Method for Composite Foam Hardness-Durometer Hardness
ISO Standard
ISO/IEC17025:1999 General Requirements for the Competence of Testing and Calibration Laboratories

Index Terms

durometer; durometer hardness; hardness; indentation hardness; micro durometer hardness; ICS Number Code 83.060 (Rubber)

Citing ASTM Standards

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