ASTM D785-08

Standard Test Method for Rockwell Hardness of Plastics and Electrical Insulating Materials

SIGNIFICANCE AND USE
A Rockwell hardness number is a number derived from the net increase in depth impression as the load on an indenter is increased from a fixed minor load to a major load and then returned to a minor load (Procedure A). A Rockwell alpha (α) hardness number represents the maximum possible remaining travel of a short-stroke machine from the net depth of impression, as the load on the indenter is increased from a fixed minor load to a major load (Procedure B). Indenters are round steel balls of specific diameters. Rockwell hardness numbers are always quoted with a scale symbol representing the indenter size, load, and dial scale used. This test method is based on Test Methods E 18. Procedure A (Section 11) yields the indentation of the specimen remaining 15 s after a given major load is released to a standard 10-kg minor load. Procedure B (Section 12) yields the indentation of the indenter into the specimen after a 15-s application of the major load while the load is still applied. Each Rockwell scale division represents 0.002-mm [0.00008-in.] vertical movement of the indenter. In practice, the Rockwell hardness number is derived from the following relationship:
where: HR=  the Rockwell hardness number, and e=  the depth of impression after removal of the major load, in units of 0.002 mm. This relation only holds for the E, M, L, R, and K scales.
A Rockwell hardness number is directly related to the indentation hardness of a plastic material, with the higher the reading the harder the material. An α hardness number is equal to 150 minus the instrument reading. Due to a short overlap of Rockwell hardness scales by Procedure A, two different dial readings on different scales may be obtained on the same material, both of which may be technically correct.
For certain types of materials having creep and recovery, the time factors involved in applications of major and minor loads have a considerable effect on the results of the measurements.
The results obtained...
SCOPE
1.1 This test method covers two procedures for testing the indention hardness of plastics and related plastic electrical insulating materials by means of the Rockwell hardness tester.
1.2 The values stated in SI units are to be regarded as standard. The values given in brackets are for information only.
1.3 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.
Note 1—This test method and ISO 2039-2 are equivalent. Procedure A of this test method is equivalent to the test method in the main body of ISO 2039-2. Procedure B of this test method is equivalent to the test method in the integral annex part of ISO 2039-2.

General Information

• Status: Historical
• Publication Date: 29-Feb-2008
• ICS: 29.035.20 - Plastics and rubber insulating materials
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.10 - Mechanical Properties

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D785 − 08
StandardTest Method for
Rockwell Hardness of Plastics and Electrical Insulating
1
Materials
This standard is issued under the fixed designation D785; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope* 3. Terminology
1.1 This test method covers two procedures for testing the
3.1 Definitions used in this test method are in accordance
indention hardness of plastics and related plastic electrical
with Terminology D883.
insulating materials by means of the Rockwell hardness tester.
3.2 Definitions of Terms Specific to This Standard:
1.2 The values stated in SI units are to be regarded as
3.2.1 indentation hardness—the resistance of a material to
standard.Thevaluesgiveninbracketsareforinformationonly.
surface penetration or plastic deformation.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Significance and Use
responsibility of the user of this standard to establish appro-
4.1 ARockwell hardness number is a number derived from
priate safety and health practices and determine the applica-
the net increase in depth impression as the load on an indenter
bility of regulatory limitations prior to use.
is increased from a fixed minor load to a major load and then
NOTE 1—This test method and ISO 2039-2 are equivalent. ProcedureA
returned to a minor load (ProcedureA).ARockwell alpha (α)
ofthistestmethodisequivalenttothetestmethodinthemainbodyofISO
hardness number represents the maximum possible remaining
2039-2. Procedure B of this test method is equivalent to the test method
travel of a short-stroke machine from the net depth of
in the integral annex part of ISO 2039-2.
impression,astheloadontheindenterisincreasedfromafixed
2. Referenced Documents
minor load to a major load (Procedure B). Indenters are round
2
2.1 ASTM Standards:
steel balls of specific diameters. Rockwell hardness numbers
D618Practice for Conditioning Plastics for Testing
are always quoted with a scale symbol representing the
D883Terminology Relating to Plastics
indenter size, load, and dial scale used. This test method is
D2240Test Method for Rubber Property—Durometer Hard-
based on Test Methods E18. Procedure A (Section 11) yields
ness
the indentation of the specimen remaining 15 s after a given
D4000Classification System for Specifying Plastic Materi-
major load is released to a standard 10-kg minor load.
als
Procedure B (Section 12) yields the indentation of the indenter
E18Test Methods for Rockwell Hardness of Metallic Ma-
into the specimen after a 15-s application of the major load
terials
while the load is still applied. Each Rockwell scale division
E691Practice for Conducting an Interlaboratory Study to
represents 0.002-mm [0.00008-in.] vertical movement of the
Determine the Precision of a Test Method
indenter. In practice, the Rockwell hardness number is derived
3
2.2 ISO Standards
from the following relationship:
ISO 2039-2Plastics—Determination of Hardness—Part 2:
HR 5 130 2 e (1)
Rockwell Hardness
where:
1
ThismethodisunderthejurisdictionofASTMCommitteeD20onPlasticsand
HR = the Rockwell hardness number, and
is the direct responsibility of Subcommittee D20.10 on Mechanical Properties.
e = the depth of impression after removal of the major
Current edition approved March 1, 2008. Published March 2008. Originally
load,inunitsof0.002mm.Thisrelationonlyholdsfor
approved in 1944. Last previous edition approved in 2003 as D785-03. DOI:
10.1520/D0785-08.
the E, M, L, R, and K scales.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
4.2 A Rockwell hardness number is directly related to the
Standards volume information, refer to the standard’s Document Summary page on
indentation hardness of a plastic material, with the higher the
the ASTM website.
reading the harder the material.Anα hardness number is equal
3
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. to 150 minus the instrument reading. Due to a short overlap of
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D785 − 08
Rockwell hardness scales by Procedure A, two different dial readingsover115arenotsatisfactoryandshallnotbereported.
readings on di
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:D785–03 Designation:D785–08
Standard Test Method for
Rockwell Hardness of Plastics and Electrical Insulating
1
Materials
This standard is issued under the fixed designation D 785; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope*
1.1 This test method covers two procedures for testing the indention hardness of plastics and related plastic electrical insulating
materials by means of the Rockwell hardness tester.
1.2 The values stated in SI units are to be regarded as the standard. The values given in brackets are for information only.
1.3 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.
NOTE 1—This test method and ISO 2039-2 are equivalent. Procedure A of this test method is equivalent to the test method in the main body of ISO
2039-2. Procedure B of this test method is equivalent to the test method in the integral annex part of ISO 2039-2.
2. Referenced Documents
2
2.1 ASTM Standards:
D 618 Practice for Conditioning Plastics for Testing
D 883 Terminology Relating to Plastics
D 2240 Test Method for Rubber Property—Durometer Hardness
D 4000 Classification System for Specifying Plastic Materials
E 18Test Methods for Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials Test Methods for Rockwell
Hardness of Metallic Materials
E 691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3
2.2 ISO Standards
ISO 2039-2 Plastics—Determination of Hardness—Part 2: Rockwell Hardness
3. Terminology
3.1 Definitions used in this test method are in accordance with Terminology D 883.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 indentation hardness—the resistance of a material to surface penetration or plastic deformation.
4. Significance and Use
4.1 A Rockwell hardness number is a number derived from the net increase in depth impression as the load on an indenter is
increased from a fixed minor load to a major load and then returned to a minor load (ProcedureA).ARockwell alpha (a) hardness
number represents the maximum possible remaining travel of a short-stroke machine from the net depth of impression, as the load
on the indenter is increased from a fixed minor load to a major load (Procedure B). Indenters are round steel balls of specific
diameters. Rockwell hardness numbers are always quoted with a scale symbol representing the indenter size, load, and dial scale
used. This test method is based on Test Methods E 18. ProcedureA(Section 11) yields the indentation of the specimen remaining
15 s after a given major load is released to a standard 10-kg minor load. Procedure B (Section 12) yields the indentation of the
indenter into the specimen after a 15-s application of the major load while the load is still applied. Each Rockwell scale division
1
This method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.10 on Mechanical Properties .
e1
Current edition approved Nov. 1, 2003. Published January 2004. Originally approved in 1944. Last previous edition approved in 1998 as D785-98 .
Current edition approved March 1, 2008. Published March 2008. Originally approved in 1944. Last previous edition approved in 2003 as D785 - 03.
2
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,[e-mail]ards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
D785–08
represents 0.002-mm [0.00008-in.] vertical movement of the indenter. In practice, the Rockwell hardness number is derived from
the following relationship:
HR 5 130 2 e (1)
w
...