ASTM_D_785_-_08_2015.pdf

Designation:D78508(Reapproved 2015)Standard Test Method forRockwell Hardness of Plastics and Electrical InsulatingMaterials1This standard is issued under the fixed designation D785;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This test method covers two procedures for testing theindention hardness of plastics and related plastic electricalinsulating materials by means of the Rockwell hardness tester.1.2 The values stated in SI units are to be regarded asstandard.The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.NOTE1This test method and ISO 2039-2 are equivalent.Procedure Aof this test method is equivalent to the test method in the main body of ISO2039-2.Procedure B of this test method is equivalent to the test methodin the integral annex part of ISO 2039-2.2.Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD2240 Test Method for Rubber PropertyDurometer Hard-nessD4000 Classification System for Specifying Plastic Materi-alsE18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 ISO Standards3ISO 2039-2 PlasticsDetermination of HardnessPart 2:Rockwell Hardness3.Terminology3.1 Definitions used in this test method are in accordancewith Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 indentation hardnessthe resistance of a material tosurface penetration or plastic deformation.4.Significance and Use4.1 A Rockwell hardness number is a number derived fromthe net increase in depth impression as the load on an indenteris increased from a fixed minor load to a major load and thenreturned to a minor load(Procedure A).A Rockwell alpha()hardness number represents the maximum possible remainingtravel of a short-stroke machine from the net depth ofimpression,as the load on the indenter is increased from a fixedminor load to a major load(Procedure B).Indenters are roundsteel balls of specific diameters.Rockwell hardness numbersare always quoted with a scale symbol representing theindenter size,load,and dial scale used.This test method isbased on Test Methods E18.Procedure A(Section 11)yieldsthe indentation of the specimen remaining 15 s after a givenmajor load is released to a standard 10-kg minor load.Procedure B(Section 12)yields the indentation of the indenterinto the specimen after a 15-s application of the major loadwhile the load is still applied.Each Rockwell scale divisionrepresents 0.002-mm(0.00008-in.)vertical movement of theindenter.In practice,the Rockwell hardness number is derivedfrom the following relationship:HR5 1302 e(1)where:1This method is under the jurisdiction ofASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.10 on Mechanical Properties.Current edition approved Oct.1,2015.Published October 2015.Originallyapproved in 1944.Last previous edition approved in 2008 as D785-08.DOI:10.1520/D0785-08R15.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available 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 standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 HR=the Rockwell hardness number,ande=the depth of impression after removal of the majorload,in units of 0.002 mm.This relation only holds forthe E,M,L,R,and K scales.4.2 A Rockwell hardness number is directly related to theindentation hardness of a plastic material,with the higher thereading the harder the material.An hardness number is equalto 150 minus the instrument reading.Due to a short overlap ofRockwell hardness scales by Procedure A,two different dialreadings on different scales may be obtained on the samematerial,both of which may be technically correct.4.3 For certain types of materials having creep and recovery,the time factors involved in applications of major and minorloads have a considerable effect on the results of the measure-ments.4.4 The results obtained by this test method are not gener-ally considered a measure o